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The Cambridge encyclopedia of space  missions, applications, and exploration

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THE CAMBRIDGE ENCYCLOPEDIA OF

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Since the launch of Sputnik in 1957, over 8 000 satellites and spacecraft have been launched from over 30 countries, costing hundreds of billions of dollars. Over 350 people have made the incredible journey beyond our atmosphere and we all benefit in countless ways from the use of space. This unique Encyclopedia aims to give a global perspective of our occupation and use of space, whether scientific, industrial, commercial, technical or military. After setting the stage by describing the space environment, orbits and ground tracks, launchers and launch sites, the authors go on to discuss the main space applications (telecommunications, navigation and Earth observation, military), as well as science missions, planetary exploration and space stations. The wealth of full-colour illustrations makes all the information highly accessible, resulting in an invaluable source for everyone interested in our use of space, and the perfect reference book for those working in or studying the space arena.

The Cambridge Encyclopedia of Space Missions, Applications and Exploration Since the launch of Sputnik in 1957, over 8000 satellites and spacecraft have been launched from over 30 countries, costing hundreds of billions of dollars. Over 350 people have made the incredible journey beyond our atmosphere and we all benefit in countless ways from the use of space. This unique Encyclopedia aims to give a global perspective of our occupation and use of space, whether scientific, industrial, commercial, technical or military. After setting the stage by describing the space environment, orbits and ground tracks, launchers and launch sites, the authors go on to discuss the main space applications (telecommunications, navigation and Earth observation, military), plus science missions, planetary exploration and space stations. The wealth of full-colour illustrations makes all the informa¬ tion highly accessible, resulting in an invaluable source for everyone interested in our use of space, and the perfect refer¬ ence book for those working in, or studying, the space arena. Fernand Verger

is Emeritus Professor of Geography at l’Ecole

Normale Superieure, Paris. He was NASA Principal Investigator for the Landsat-1 and -2 programme, and project director of the preliminary programme for assessing the SPOT satellite. Isabelle Sourbes-Verger

is a researcher at the Centre National de

la Recherche Scientifique and Fondation pour la Recherche Strategique, Paris. is a cartographic engineer at the Centre National de la Recherche Scientifique and has worked on many Raymond Ghirardi

geographical and geopolitical projects. is a researcher at the Fondation pour la Recherche Strategique, and Associate Professor at the Universite de Marne

Xavier Pasco

laVallee.

The Cambridge Encyclopedia of

Space Missions, Applications and Exploration Fernand Verger, Isabelle Sourbes-Verger, Raymond Ghirardi

with contributions by Xavier Pasco Foreword by John M. Logsdon Translated by Stephen Lyle and Paul Reilly

Cambridge UNIVERSITY PRESS

PUBLISHED BY THE PRESS SYNDICATE OF THE UNIVERSITY OF CAMBRIDGE The Pitt Building,Trumpington Street, Cambridge, United Kingdom CAMBRIDGE UNIVERSITY PRESS The Edinburgh Building, Cambridge, CB2 2RU, UK 40 West 20th Street, New York, NY 10011 -4211, USA 477 Williamstown Road, Port Melbourne, VIC 3207, Australia

EAST SUSSEX"

Ruiz de Alarcon 13,28014 Madrid, Spain Dock House, The Waterfront, CapeTown 8001, South Africa http://www.cambridge.org

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English translation © Cambridge University Press 2003

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MARK. French edition © Editions Belin 1997

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This book is in copyright. Subject to statutory exception

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and to the provisions of relevant collective licensing agreements,

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no reproduction of any part may take place without the written permission of Cambridge University Press.

Previously published in French as Atlas de geographic de 1'espace First published in English 2003

Printed in the United Kingdom at the University Press, Cambridge

Typeset in Joanna 10.25 /12.5 pt, in QuarkXpress™ [ds]

A catalogue record for this book is available from the British Library

Library of Congress Cataloguing in Publication data Verger, Fernand. [Adas de la geographie de 1'espace. English] The Cambridge encyclopedia of space: missions, applications, and exploration/by Fernand Verger, Isabelle Sourbes-Verger, Raymond Ghirardi; with contributions by Xavier Pasco, p.

cm.

Includes bibliographical references and index. ISBN 0 521 77300 8 1. Astronautics-Encyclopedias. 2. Rocketry-Encyclopedias. 3. Outer space-ExplorationSpace Policy-Encyclopedias. I. Sourbes-Verger, Isabelle. II. Ghirardi, Raymond. III.Tide. TL788.V48 2002 629.4'03-dc21

ISBN 0 521 77300 8 hardback

2002067408

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Contents Foreword vii Preface ix

Chapter One

The environment of outer space Deep space Near space

2 4

Chapter

Two

Orbits 9 General principles 10 Sun-synchronous satellite orbits 16 The geostationary satellite orbits 20 Lagrange points and associated orbits Space probe orbits 26

25

ChapterThree

Ground tracks

31

Overview 32 From orbit to Earth: mapping the ground track Types of ground track 39 Ground tracks and orbital cycles 42

Chapter Four

Occupation of space 45 The geography of spaceborne objects 46 Satellites and probes 57 Civilian and military applications 61

vi | Contents

ChapterTen

Chapter Five

Space policy and budgets

Telecommunications

7

6

Budgets and space activities throughout the world Russia and the CIS Republics 73 The United States 79 Europe 87 Japan 95 China 99 India 101 Israel, Canada, Brazil and Australia 103

68

279

Geographical constraints 280 Frequencies and reservations 285 Missions 288 Geography of space telecommunications International systems 298 Regional systems 308 National systems 314

296

Chapter Eleven Chapter Six

Positioning and navigation

Access to space 105

Overview 318 Systems using downlink signals 318 Systems using uplink signals 328

Overview 106 International comparison 107 Russia and the CIS Republics 119 The United States 129 Europe 141 Japan 149 China and India 153 Israel, Brazil and other countries 157

Chapter Twelve

Military applications of space Status of military activity 334 Collection of information 336 Telecommunications 349 Space: the new battlefield? 353

Chapter Seven

Circumterrestrial scientific missions Scientific research 160 Study of the Earth 162 Observation of the circumterrestrial environment Astronomical observation 180 Other fields of investigation 187

159

Chapter Thirteen 167

Chapter Eight

Exploration beyond geocentric orbit Exploration and geography 192 The Moon 193 Solar System observation missions

200

Chapter Nine

Earth observation

225

Overview 226 Sensors 228 Images of the Earth 238 Meteorology 241 Remote sensing of terrestrial resources 247 Optical remote sensing systems 250 SAR-equipped Earth resource systems 266 Remote sensing-the way ahead 273

317

191

Living in space

359

Human occupation of space 360 First steps in space 364 The first space stations 367 The Space Shuttle, Mir and Buran 370 The International Space Station 375 Future Chinese programme 381

Bibliography Internet sites Index 390

383 385

333

Foreword

This is an exciting volume, hard to put down. Its coverage is

The first artificial Earth satellite went into orbit less than a

literally cosmic in scope. No area of space activity goes unex¬

half-century ago. This volume sets out in both words and

amined. The book’s visualizations of various aspects of space

images humanity’s achievements, benefits, and aspirations

activities and capabilities are unique, provide new perspec¬

since that historic step towards homo sapiens a space-faring

tives on what actually goes on in the region beyond the

species. It provides an understanding of the physical, eco¬

atmosphere. Just to pick one example, Figure 4.3 is a remark¬

nomic, and political realities that must be taken into account as

able achievement. It summarizes in one chart the whole

next steps are planned. It depicts the many uses that have

history of space activity in a clear and immediately under¬

already been made of the capability to put people and machines

standable fashion.To see the clustering of satellites in various

into space, and suggest next steps in space development.

Earth orbits, and then the relatively few space probes that

As the volume discusses the building blocks of space activ¬

have explored the Solar System away from Earth, charts the

ity - spaceports, launch vehicles, and various space missions

path of space development to date in a fashion that dramati¬

themselves, its words are complemented throughout by

cally improves upon what can be communicated by words

innovative visual and graphical presentations and by well-

alone. There are many, many similar standout depictions of

chosen photographs. The text is of course an essential element

complex information throughout the volume.

of any encyclopedia, and the text here both provides compre¬

Most of us who have spent long careers working in the

hensive and reliable information and offers penetrating

space sector are wont to say ‘space is just a place,’ then

insights regarding the factors that shape activity in space. That

ignore the implications of that reality as we discuss what

said, it is its visual material that sets this volume apart from

happens in orbit and beyond. Not so Fernand Verger and his

any previous attempts to capture in one place the complexity

colleagues. Professor Verger is one of the most distinguished

of space activity. Professor Verger and his associates have spent

geographers in France, and his influence on this volume is

many years perfecting their depictions of space activity, and

evident. The Cambridge Encyclopedia of Space takes a geographical

they have made a real contribution to our appreciation of how

perspective whenever possible. It first of all describes outer

far we have come in opening up the space frontier, and to the

space in physical terms, as an environment with its own

increasingly

natural characteristics that both facilitate and limit what can

exploitation. The Cambridge Encyclopedia of Space will be an essen¬

be done there. This unique perspective sets the stage for the

tial reference work for every space professional and a boon for

rest of the work.

those just learning about this new arena for human activity.

global

character

of space

John M. Logsdon Director, Space Policy Institute The George Washington University Washington, DC, USA

exploration

and

Preface

Over the last forty years, circumterrestrial space has been

from the chapter specifically devoted to space policy, the

gradually occupied as unmanned satellites have been put into

means of access and main areas of application are presented

orbit to carry out a range of different functions, and in a

to show how the various programmes express different

more limited way, as human beings have also increased their

national preferences and their consequences for world

presence, annexing the closer regions of the cosmos to the

affairs. The geopolitical aspect of the space phenomenon is

inhabited world. It has hence become possible to build up a

indeed a key feature, since satellites procure for us a new

geography of space, and it is this idea that lies at the heart of

vision of our planet and a clearer picture of its resources.

the present work.

Hence, remote sensing which is so important for carto¬

Designed along the lines of an explanatory atlas, this ency¬

graphic applications raises the problem of how data should

clopedia allows the reader to understand the extent to which

be made available, for it is as relevant to national indepen¬

space has been occupied and to follow the main motivations

dence and international security as it is to territorial devel¬

underlying its development. To begin with, it provides a car¬

opment. In the same way, the flow of information, by

tographical view of this occupation, briefly specifying the

telephone or television, for positioning or other purposes,

conditions that prevail in the medium and the physical laws

provides the subject for a cartographic representation which

that hold sway over the use of circumterrestrial space. Many

illustrates the main areas of exchange, the weakened and

constraints must be faced in space development. These con¬

transformed notion of border, and the appearance of ever

straints explain the unequal distribution of satellites and

sharper international features heavily dominated by the

probes gravitating in a number of different orbits, nearby or

United States. Finally, the navigation programmes are closely

distant, circular or eccentric, equatorial, polar or other,

linked to questions of strategic independence in a field

depending on their mission, whether it be for exploration of

where applications are still emergent.

our cosmic neighbourhood or further afield, civilian Earth

Space activities thus have many repercussions and, on a

observation, telecommunications, military surveillance, or

global level, increase the weight of the dominant powers,

human occupation.

whether they be military or civilian. These manifest them¬

However, space-based activities can also be considered in

selves on an economic level through the development of new

terms of their relationship to Earth. The successive passages of

systems made possible by state-of-the-art technology and

satellites criss-cross the whole surface of our planet, their

answer to a growing need to dominate the markets. Space

tracks winding around it like the thread around a ball of wool.

bestows an undeniable advantage upon those that lay claim

Satellites supply a new image of the globe and encourage links

to it, not only by the information it offers, but also by the

between different peoples. At the same time, the complexity

possibilities for direct intervention which it opens up.

of space technology creates a genuine hierarchy amongst the

Finally, the occupation of space by human beings and pro¬

countries of the world, reasserting the traditional balance of

jects to set up long-term space outposts lead to new

power on Earth, yet introducing new features. The main steps

prospects, although sensitive to the vacillation of political

in space conquest have led to the steady constitution of what

commitment.

appears today to be an exclusive club of space powers.

Going beyond a simple description of the way current

However, the different activities have been mastered to quite

projects attempt to occupy space, this work aims to provide

varying degrees. Almost all countries around the planet now

a conceptual basis for a genuine geography of space,

use space systems. Many are those who operate the satellites

without which it would be difficult to comprehend its

that only a much more restricted group of countries are able

development or the growing number of related issues in

to put together. On the other hand, very few nations can pro¬

today’s world.

vide their own launch capacity, and even fewer can claim to master the whole range of manned and unmanned, civilian and military space resources.

Acknowledgements

The present book aims to describe and account for space

Images have been supplied by CNES, Spotlmage, DLR, ESA,

endeavour around the world and to provide a careful analy¬

GRGS, ImageSat, ISAS, ISRO, NASA, NASDA, NRSA, Radarsat,

sis of the policies that guide the great space powers. Apart

Space Imaging.

Chapter One

The environment of outer space

Deep space

In the Solar System distance measurements are commonly

Trojans around 5 AU (see fig. 8.30).

expressed in astronomical units (AU). One AU is the length of the

■ Several hundred other objects, similar to asteroids, which

semi-minor axis of the Earth’s orbit, that is, 149 597 870 km.

gravitate beyond the orbit of Neptune. These form the

In the distant universe, which extends beyond the range of

Kuiper Belt. Pluto and its moon Charon are now consid¬

today’s probes, they are expressed in light years (1 light year

ered as members of this group.

= 9.461 x 1012 km) or parsecs (1 parsec = 3.26 light years). Deep space refers to the central part of the Solar System

■ The comets, which have eccentric orbits, and primitive tra¬ jectories with semi-major axes measuring several tens of thousands of AU.

(fig. 1.1).This contains: ■ one star, the Sun, of radius 696 000 km,

In addition, like the rest of the interplanetary medium, deep

■ the nine principal planets whose mean distances from the

space is filled with:

Sun, or mean heliocentric distances, vary between 0.39 AU for Mercury and 3 9.44 AU for Pluto (see table 1.1).

■ a flow of ionised particles originating in the Sun and known as the solar wind,

The motion of the planets against the celestial sphere of

■ interplanetary dust.

fixed stars has been observed since the earliest times,

Certain parameters are used to locate positions of celestial

earning them the name of wandering bodies (from the

bodies in the Solar System relative to Earth.

Greek

The geocentric distance depends on both the orbit of the celes¬

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10 cm

First flight

MK-4 M

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MSU-SK

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MVIRI

Meteosat 3-7

MSU-S

Okean-Ol 1-4, Sich 1

MSU-M

Okean-Ol 1-4, Sich 1

VHRSR

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VISSR

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ERS 1

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ERS 2

LISS-3

IRS 1C, ID

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IRS 1C, ID

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1996

MOS

1996

Priroda

AVNIR

1996

ADEOS

Priroda

POLDER

1996

ADEOS

OCTS

1996

ADEOS

MVIRSR

1997

Feng Yun-2 1

Figure 9.13. The spectral bands used by the main imaging sensors launched and planned in 2002.

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1 USA

Russia Ukraine Europe Canada China China-Brazil 1 India Japan

Sensors

MICROWAVE

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First flight

Satellite

SeaWiFS

1997

Seastar (OrbView 2)

VIRS

1997

TRMM

HRVIR

1998

SPOT 4

Vegetation

1998

SPOT 4-5

AVHRR-3

1998

NOAA 15-L-M

ETM+

1999

Landsat 7

1999

Feng Yun-1 3

OCM

1999

IRS-P 4

MSU-A

1999

Okean-O

MSU-V

1999

Okean-O

1999

Ikonos 2

CCD Cam

1999

CBERS 1, 2

IRMSS

1999

CBERS 1, 2

WFI Cam

1999

CBERS 1, 2

ASTER

1999

Terra (AM 1)

MISR

1999

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1999

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2002

MERIS

2002

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HRST (NEMO) Resource 21

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ARIES X Star

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Satellite nationalities USA Russia Ukraine Europe Canada China China-Brazil India Japan "1 Australia

Seasat

SAR

1978

SIR A

1981

STS 2

SIR B

1984

STS

SAR

1991

Almaz

SIR C

1994

STS 68

X-SAR

1994

STS 68

AMI SAR

1991

ERS 1-2

SAR

1992

JERS1

SAR

1995

Radarsat 1

Travers SAR

1996

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2002

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237

Images of the Earth

The mass of images supplied by the various sensing systems

concept when referring to images obtained by scanning is

described above form the satellite Earth observation archives,

that of the ground area — field or spot — corresponding to a

supporting meteorology and remote sensing in the strictest

pixel or the closely related idea of Ground Sample Distance

sense but also military reconnaissance.

(GSD), both of which are sometimes regarded by extension

With the growing stockpile of such images comes the need for simple referencing

as units of resolution.

principles. The principles

Working from the concepts of global field of view, instan¬

adopted may be based on the themes treated in the images -

taneous field of view and resolution, three main scalar levels

clouds, water, land - or on the geographical coordinates of

can be defined (fig. 9.14):

the region surveyed, this being the method favoured for

A: planetary images: these cover an expanse of the planet

indexing data from the major satellite remote-sensing sys¬

from limb to limb and are acquired from a high altitude

tems: Landsat with the World Reference System and SPOT

- generally from geostationary orbit some 36 000 km

with the SPOT Reference Grid (Grille de Reference SPOT, GRS).

above the Earth. Images at this level have kilometre-range

Within these overall structures, straightforward criteria are

resolution. They are used in meteorology and global cli¬

then required for classification to cope with the different

mate research (radiation budget etc.).

acquisition modes and - a greater challenge still - the very

B: Images at regional level: these cover smaller expanses and

many forms of image processing. These criteria are needed to

are acquired from lower altitudes. Ground resolution is

assign images to categories for subsequent archiving but also

in the 100 m or 10m range. Applications here are car¬

for educational purposes.

tography and terrestrial resource surveying.

Scalar levels A simple approach to the classification of

images

ground resolution

altitude (km)

10 - 2.5 km

36 000

examples of satellites

major uses

Meteosat

meteorology

GOES

climatology

Kosmos 1940

oceanography

satellite images is based on the concept of scale - scale of field and resolution. Strictly speaking, the concept of scale is fully meaningful only when applied to images in the very literal pictorial sense. The photographic film used in the KVR 100 camera on SPIN 2 (SPace INformation) or in the Metric and Large Format Cameras on Shuttle Spacelab missions

meteorology

1500 1-2 km

Meteor

to 800

NOAA 15

records images for which there is a geo¬

Earth resources studies

metric relationship between ground dis¬ MOS

tances and the distances on the original film. But in the case of a scanner sweeping the ground and collecting signals which

900 120 - 25 m

define the luminescence of the instanta¬

Landsat 1-5

cartography

to

JERS

700

Almaz

Earth resources studies

ERS

neous field of view on the ground, the concept of scale begins to blur, coming to mean the basic ground unit - the area represented by one picture element

20 -10 m

900

SPOT 1-4

cartography

to

Shuttle (metric camera)

Earth resources studies

250

(pixel), the basic constituent of an image. An image consisting of a patchwork of

\

pixels can be built up to the desired scale 800

in the same way that a true photograph taken by the Metric Camera or MKF 6 can be enlarged or reduced at will.

4-0.3 m

to 150

While the criterion of scale is satisfac¬ tory for true photographs, a more helpful 238

Figure 9.14. Classification of satellite images by scalar level.

Yantar KH 11 Helios 1A-B Ikonos 2

military observation arms control verification urban cartography

Images of the Earth

C: Images at local level: these cover restricted areas and are

|

Primary images acquired by satellite remote sensing are

acquired by vertical or oblique viewing, often from very

used far less widely than the derived products, in sharp con¬

low altitudes. Metre and decimetre range resolutions are

trast to the situation in aerial photography interpretation.

obtained. Initially used for military reconnaissance pur¬

Secondary images, which exist in much larger quantities, can

poses, these images are now finding civil applications at

be classed according to various criteria. One of the most

metre-level resolution.

straightforward is whether only one or more than one pri¬

Between these main levels there are many intermediate lev¬

mary image was used to produce the derived image. Images

els. Limb-to-limb images acquired by the AVHRR sensor on

derived from a single image are described as monogenic and

NOAA satellites are, for example, situated between levels A

those resulting from a combination of images are called

and B. Each pixel represents a ground area in excess of 1 km2

polygenic (fig. 9.15).

and utilisation is a mix of meteorology and terrestrial

Monogenic secondary images are derived from a single

resource surveying (location of local upwellings, study of

image. They may be the product of enlargement, reduction,

Sahel vegetation etc.). Similarly, SPOT imagery and photos

correcting geometric anamorphosis, change in projection or

taken from the Mir space station are positioned somewhere

contrast adjustments. Contrast may be

between levels B and C.

accentuated by

extending the grey scale in such a way that the darkest grey in the entire image is shown as black and the lightest grey as

Types of processing

white. This operation can also be performed in a small

Another system of classification is based on the nature of the

mobile window to heighten local contrasts in the image

image itself and the type of processing applied to it. This

without regard to relative values in the image as a whole.

scheme rests on a distinction between primary and derived

Changes in the grey scale do not necessarily obey a monoto¬

or secondary images. Images in the first category are those

nic function and may substitute for initially rising values,

which have retained the geometry of acquisition and have

values which rise and fall alternately.

undergone no specialised processing. They can be termed

Other modifications may be governed by probability.

‘primary images’, although their primary status is difficult to

Images may for example be created in which each grey

define. The negative of a photographic film remains a pri¬

tone occupies an equal surface area or relates to a gaussian

mary image even after development. But can an image

distribution.

obtained by visualising an analog recording on film still be

The original images may be simplified by reducing inten¬

regarded as a primary image? When an image is digitised by

sity levels or by sampling information elements and reduc¬

sampling, is the output a primary or a secondary image?

ing the number of pixels. It is also possible by filtering to

PRIMARY IMAGES

SECONDARY MONO¬

IMAGES

POLYGENIC

GENIC

external

internal

time

spectrum

space

mm

data inside

outside



1

geometric

accentuation of general contrast

scale

1

1_1

treatment

superimposition

kJ‘

'*$

mosaic

accentuation of local contrasts

geometric

analysis

classification gradient extraction

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f

1 r

1 r

ir

y

£ false-colour composition

multiband classification

differential image

diachronic mosaic

ir

r\

Wm

smoothing

r

hypsometric image

Figure 9.15. Types of satellite remote-sensing image resulting from the most common forms of processing.

multiple resolution image

space-map, GIS image

239

240

;

Earth observation

replace the primary image with an image conveying the dif¬

genuinely panoramic view for any given viewpoint. By com¬

ferences in value between adjacent pixels (a gradient image)

puter processing it is thus possible to derive a new image

or alternatively with a smoothed image in which each origi¬

corresponding to a viewpoint independent of the actual view¬

nal pixel is replaced by the pixel most frequently encoun¬

points of observation. What is really useful here is the direc¬

tered in a specified area.

tional aspect — the diachronic treatment which necessarily

Polygenic secondary images are composite products built

goes with it is more of a handicap than anything else as there is

up from several primary images in an internal process rely¬

always the possibility of some change to objects between two

ing solely on remote-sensing data.

image acquisitions. This problem can be overcome to some

The most common type is the conventional false-colour

extent by an arrangement used on some satellites - on JERS 1

composite in which each of three primary images acquired

channels B3 and B4 for example - in which forward viewing

simultaneously in three spectral bands by a multiband sensor

is combined with nadir viewing in the same revolution; this

is translated by one of the sensitive layers of a colour film

limits to just a few fractions of a second the time-lag between

using the subtractive (cyan, magenta, yellow) colour process

two stereoscopic acquisitions. The POLDER system equipping

or by the colours of the TV screen using additive (green,

the ADEOS series works in the same way, combining fractions

blue, red) colour mixing. As computer displays have come

of wide-angle images acquired from two viewpoints some

into more widespread use, subtractive synthesis has given

distance apart.

way to additive mixing of the primary colours. This is essen¬

Scalar polygenic processing involves combining images at

tially a spectral technique for deriving images and spectral

varying scales. Combining an Ikonos multispectral image with

polygenic processing can form the basis for many other

a pixel area of 4 m x 4 m and a panchromatic image made up

types of processing, such as classification by segmentation or

of 1 m x 1 m pixels amounts to double polygenic processing -

by clustering around mobile points.

both spectral and scalar - insofar as the combined data relates

Diachronic processing — another form of polygenic treat¬ ment — involves combining images acquired at different

to different spectral bands and unequal surface areas. External polygenic processing comes into play where data

dates. This may simply involve superimposing a positive

acquired otherwise than by satellite remote sensing is com¬

image acquired at one date and a negative image acquired at

bined with satellite data. One impressive example of such

another. Differences between the two images thus appear as

treatment is the production of maps in which a satellite image

areas of lighter or darker shading. Another approach is to use

is used as background, information of a topographic or

diachronic data to reference pixels so as to characterise fami¬

toponymic nature being superimposed on the image. Geo¬

lies by their evolution. Images of this kind have been pro¬

graphical Information Systems (GIS) which choose to incor¬

duced to define areas of coastal erosion and accretion in the

porate satellite data often generate considerable demand for

time interval between two given successive satellite passes or

polygenic images of this type. In some cases, administrative

again to monitor the evolution of vegetation frontiers or

and statistical data are combined with classifications based on

shrub die-back in zones subject to desertification. Derivation

multispectral imagery. This particular technique, which calls

of images by diachronic composition has other applications

for a firm grasp of the geometry of essentially heterogeneous

too, one being to fill localised lacunae in particular images.

data coupled with a sound understanding of the subject mat¬

Small isolated clouds may for example mask certain points

ter, is becoming an increasingly widespread feature of the

on the surface of the Earth but there is every chance that the

civil and military exploitation of satellite data.

cloud positions will be different on images acquired on sub¬

Images can therefore be differentiated by form of deriva¬

sequent days: by taking the maximum values for thermo¬

tion — from one, or more than one primary image — and, in

graphic images of the same locations several days running, it

the case of polygenic derivation, by the treatment applied to

is generally easy enough to eliminate the offending clouds —

them, which may be spectral, diachronic, directional or

which are colder than the ground. Similarly, it becomes pos¬

scalar, and by whether non-satellite inputs are included in

sible to draw up notional maps of small regional units by

the process. These forms of differentiation determine the

combining the changing faces of landscapes over a year.

nature of the informational content. Images are distin¬

Directional polygenic treatment involves combining images of the same area acquired from different viewpoints. This is

guished too by the types of treatment applied to the source images in order to generate them.

the only available means of reconstituting terrain contours

The widening range of data sources and forms of process¬

from two images. A pair of SPOT images acquired at different

ing is attributable in part to the growing number of satellites

angles in the course of two different orbital revolutions can

— which feed enormous collections of images — and in part

thus be used to produce digital elevation models. Digital mod¬

to advances in computer-based image processing techniques.

els of this kind, in conjunction with the colours deduced from

The biggest problem now facing users is that of deciding

the radiometric readings indicated by a multispectral image,

what images to choose and what treatment to apply to them

can by computer calculation be used to derive and display a.

for a given application.

Meteorology

Meteorology offers a range of practical applications which

casts for the general public. They are of interest too in agri¬

make a major contribution to human safety and the security

culture as an input to forecasting of frost, rainfall and fog and

of air and sea transport. Thanks to satellite data, the paths of

to research into snowcover and the effects of drought.

tropical cyclones for example can now be predicted far more

Climatology is another area in which meteorological satel¬

reliably. On the basis of such predictions, shipping is rerouted

lite data is of interest. While this discipline is less demanding

and preventive action is taken in the zones through which

than meteorology in terms of how quickly data must be sup¬

hurricanes pass. Meteorological information is also of consid¬

plied, it does require much longer time sequences.

erable importance for the conduct of military operations and

The contribution which observation from space could

for the planning of photographic reconnaissance missions -

make to meteorology was recognised at an early stage,

hence the existence of dedicated military programmes such as

prompting the launch of non-geostationary satellites in the

the Defense Meteorological Satellite Program (DMSP).

first instance and, from 1966 onwards, geostationary satel¬

There is a permanent demand for meteorological data

lites (fig. 9.16).

from the media with their requirement for short-term fore¬

Figure 9.16. Time chart of meteorological satellites.

241

242

i

Earth observation

Non-geostationary satellites

and Meteor III from 1985. There can be no doubt that the

Explorer 7, a satellite which measured the overall radiation

integration of civil and military activity within the Soviet mil-*

of the Earth and Sun, was launched as early as 1959, followed

itary-industrial complex made for synergies between the

as from 1960, by the TIROS series, a family of experimental

various programmes and today, in a difficult economic envi¬

satellites designed to gather images of the cloud system. This

ronment, is helping to maintain a basic capability.

was the first family of satellites to couple measurements in

In the United States, with 40 or so dedicated military satel¬

the visible and the thermal infrared. The early satellites in the

lites already launched, a May 1994 presidential directive gave

TIROS series (1-7), with an inclination of around 40°, could

official impetus to efforts to forge closer links between the

not provide full coverage of the Earth but they flew at suffi¬

NOAA and DMSP programmes. The first satellite in the result¬

ciently low altitude to support adequate ground resolution,

ing new series is scheduled for delivery in 2005.This should

and this despite the relatively poor angular resolution offered

reduce by half the number of satellites that are needed, with

by the infrared sensors available at that time.

an accompanying improvement in performance.

TIROS 8 saw a switch to Automatic Pictures Transmission

The low orbits occupied by polar satellites ensure high

(APT) to a large number of image receiving stations and, as

ground resolution and hence a detailed description of cloud

from TIROS 9, it was decided to opt for the sun-synchronous

formations, landforms and seascapes and of the distribution

orbit, from which the Earth can be observed almost in its

of surface temperatures. Comparison of data acquired at dif¬

entirety with constant solar illumination.

ferent dates in both the visible and the thermal infrared

The TIROS satellites paved the way for the Environmental Science Services Administration (ESSA) series, characterised

bands is also facilitated by the mostly sun-synchronous orbits occupied.

by improved spatial resolution despite higher altitudes of

An ability to determine cloud and ground temperatures is

around 1600 km. In parallel to this effort on the civil front,

of great interest, as is information about temperatures at the

the Americans were also proceeding with a first series of

surface of the oceans — and here meteorological satellites

launches under the Defense Meteorological Satellite Pro¬

today make a substantial contribution to oceanography. Data

gramme (DMSP).

acquired in the visible and the thermal infrared by, for exam¬

With its Nimbus experimental satellites, NASA was able to

ple, NOAA satellites have contributed much to an improved

explore numerous innovations, with particular emphasis on

understanding of upwellings and of the horizontal move¬

techniques for vertical sounding of the atmosphere and,

ments of water masses of differing temperatures. Such data is

with the last satellite in the series, on the detection of atmos¬

also widely used in the study of landscape evolution. The

pheric and marine pollution. A number of sensors developed

AVHRR sensors equipping NOAA satellites supply data in

thanks to the Nimbus programme went on to equip the

either Global Area Coverage (GAC) or more frequently Local

ITOS-NOAA operational series managed by the meteorologi¬

Area Coverage (LAC) form. GAC data relates to 4 km x 3.3 km

cal administration; the replacement as from NOAA 6 of the

ground patch areas at the nadir point while LAC data describe

VHRR sensor by the AVHRR version saw a sharp improve¬

a smaller basic unit, 1.1 km x 1.1 km at the nadir point.

ment in the performance offered by these satellites.

The FengYun 1A, IB and 1C satellites launched by China

These weather satellites may also carry various kinds of

in 1988, 1990 and 1999 respectively operate from sun-

measuring instrument. TIROS-N and the subsequent NOAA

synchronous orbits at an altitude of 890-900 km and have

satellites were equipped with a TIROS Operational Vertical

similar functions to those of the American NOAA satellites.

Sounder (TOVS) system consisting of three instruments: ■ the High Resolution Infrared Radiation Sounder (HIRS)

Orbview 1, launched in April 1995 by Orbimage Corpo¬ ration, is the world’s first commercial meteorological satel¬

for establishing the humidity and temperature profile of

lite. From its sun-synchronous orbit at an altitude of 740 km,

the atmosphere up to an altitude at which atmospheric

Orbview 1 supplies, thanks to its Optical Transient Detector

pressure is no more than 10 hectopascals;

(OTD), meteorological forecasting data but also cloud-to-

■ the Microwave Sounding Unit (MSU) for establishing the

cloud lightning imagery which it would be impossible to

temperature profile of the atmosphere in the presence of

obtain from the ground. Lightning imaging research has also

cloud cover;

been performed - with greater frequency though limited to

■ the Stratospheric Sounding Unit (SSU) for establishing

the intertropical zone — by the US—Japanese Tropical Rainfall

the temperature profile of the stratosphere.

Measuring Mission (TRMM) satellite launched in 1997 (see

The Soviet Union, and subsequently Russia, built up sub¬

chapter 7). TRMM features a number of NASA-supplied

stantial space meteorology programmes, though these got

instruments - a 5-channel Visible Infra-Red Scanner (VIRS)

underway a little later than their American counterparts.

offering 2 km resolution, the 9-channel TRMM Microwave

Launch of a number of Kosmos experimental craft - three-

Imager (TMI) and a Lightning Imaging Sensor (band centred

axis stabilisation being introduced as from 1966 with Kosmos

on 0.7774 |xm) offering 5 km resolution at the nadir — and

122 and inclinations close to 81° being achieved on Kosmos

the NASDA-supplied Precipitation Radar (PR) instrument.

144, 156 and 184 — was followed by that of three series of

MEGHA-Tropics is a project allowing for most frequent pas¬

Meteor satellites, Meteor I as from 1969, Meteor II from 1975

sages above tropical cyclones studied by ESA.

Meteorology

j

Lastly, the European organisation Eumetsat is pressing ahead with the METeorological Operational Satellite (METOP) programme, which involves providing sun-synchronous satellites to meet, in cooperation with NOAA, meteorologi¬ cal requirements over the years 2001—2010. The METOP 1 satellite, which will effect its descending node pass at 09:00, is built round a downsized Envisat platform carrying a series of sensors, including an AVHRR 3 (6 spectral bands from 0.68 |xm to 12.5 |xm), an HIRS 3 (20 spectral bands from 0.69 |im to 14.95 |xm) and two Advanced Microwave Sounder Units (AMSU A1 and A2) - operating 13 and 2 channels respectively — which will establish atmospheric humidity and temperature profiles. Figure 9.17. Satellites making up the World Weather Watch. The long tradi¬

Geostationary satellites

tion of public service and international cooperation in meteorology entered a

Geostationary meteorological satellites came on the scene

new phase with the advent of satellites. Creation of the World Weather Watch

somewhat later than their non-geostationary meteorological

is a fine example of this new departure.

counterparts. Geostationary satellites were first used for mete¬

The World Weather Watch arose out of a United Nations recommendation

orological purposes by NASA with its Application Technology

made in 1961 to the World Meteorological Organisation (WMO), an agency

Satellites (ATS) designed to test technologies that could benefit

which had been in existence since 1951. Its brief is to provide operational ser¬

from the geostationary environment for various types of appli¬

vices supported by a global system for observation of the circulation of cloud

cation. Although the bulk of the tests were devoted to telecom¬ munications, meteorology was by no means absent from this

masses, by means of geostationary and non-geostationary satellites belong¬ ing to various member states of the organisation. The system is built around a core structure of five geostationary satellites

American programme and indeed it was ATS 1 which in 1966 supplied the first-ever images of the Earth from 36 000 km and ATS 3 which a year later sent back the first colour images from

positioned around the Earth in such a way as to provide global coverage, except for the polar caps up to 8° from the poles. The five radii indicate the orbital positions designated by the WMO for the ring of geostationary satel¬

the same orbit. Meteorology from the Clarke orbit made its

lites. They are complemented by a number of satellites in near-polar orbit,

operational debut with the Synchronous Meteorological Satel¬

which provide coverage of the higher latitudes which cannot be seen from the

lites (SMS 1 and 2) launched in 1974 and 1975.The SMS satel¬

equatorial plane. They also supply more detailed information about cloud

lites form part of the ring of geostationary meteorological

cover and marine/continental temperature distributions.

satellites providing complete coverage of planet Earth with the exception of the very high latitudes, which are not observable

bands, mainly in the SWIR, are added — GOES 9 for instance

from this specific equatorial orbit.

gathers data in the following five spectral bands: 0.55 |xm-

This ring coverage is supplied by satellites occupying the following five stations (fig. 9.17): ■ 140° east: Geostationary Meteorological Satellite, Japan (GMS 5 since 1995); ■ 74° east: Insat, India (Insat 2D since 1997; Insat 2E is on standby since 1999 at 83° east);

0.75 |xm, 3.80 (jim-4.00

(Jim,

6.50 p.m-7.00 p.m, 10.20 (xm-

1 1.20 |xm and 11.50 p.m-12.50

(Jim.

Meteosat Second Generation (MSG) satellites are equipped with a number of new sensors, including the Spinning Enhanced Visible/IR Imager (SEVIRI) which will scan the entire visible segment of the globe every quarter of an hour

■ 0°: Meteosat, Europe (Meteosat 7 since 1997);

in 12 channels. Another of the sensors, the High Resolution

■ 75° west: Geostationary Operational Environmental Satel¬

Visible (HRV) will offer a 1 km ground resolution in the 0.50

lites, USA (GOES 10 since 1997); ■ 135° west: Geostationary Operational Environmental Satellites, USA (GOES 9 since 1996).

|xm-0.90

(Jim

spectral band. MSG 1 has been launched in

August 2002. Data from geostationary satellites can be received by a

In addition to these nominal orbital positions, most satellites

large number of stations and indeed satisfactory dissemina¬

are stationed at one time or another in different waiting

tion and effective utilisation depends on this.

positions (immediately after launch) or standby positions

In the case of the Meteosat series for example, data is digi¬

(at the end of their operational lives or following operating

tised on board the satellite, transmitted in real time to

incidents). Thus when GOES 6 (GOES East) failed on 21 Jan¬

ground, where it is geometrically corrected, and then

uary 1989, GOES 7 (GOES West) was moved first, in Spring

retransmitted to Meteosat, which distributes it. Digital pro¬

1989, from 75° west to 108° west and again, in Autumn the

cessing is performed by Primary Data User Stations (PDUS)

same year, to 98° west. This failure left only four satellites

and analogue processing by Secondary Data User Stations

operational in 1989 (fig. 9.18).

(SDUS).There are some 2000 secondary stations but a much

These satellites gather data primarily in a visible (fig. 9.19)

smaller number of primary stations. SDUS receive Wefax

and a thermal infrared band. In some cases other spectral

analogue data on a free access basis whereas, for part of the

243

244

Earth observation

(1980)

O SMS

2 (1975) O—

SMS 1 (1974)

-O (1980)

GOES 2 (1977)

O

METEOSAT 1 (Dec. 1977 - Apri

(Nov. 1981 - Sept.

GOES 4 (1980) O GOES 5 (1981)

GOES

6

(1983)

i=rr

O

(1989) O

(Feb. 1993 to May 1995)

(1989) (

•O GOES 7 (1987)

5

(1992) (1995)

t

(1996)

O

O

(1996)

(March 1989) ^

(Feb. 1990 - April 1990)

(June

GOES 8 (1994)

O

Q--O

(1995)

GOES 10 (25 April 1997)

(July 1997) (

METEOSAT 7 (2 September 1997) 4

lower part of the figure shows changes in the positions of satellites until their transfer to disposal orbits above the geostationary orbit.

digital data received by PDUS, encryption arrangements and

gramme (MOP) comprising three new operational satellites:

royalty payments have been introduced. Meteosat also dis¬

Meteosat 4, in service from 1989 to 1995, and Meteosat 5

tributes data supplied by Data Collection System (DCS)

and 6, launched in 1991 and 1993 respectively. In 1997

In view of the success of meteorological satellites, the various experimental programmes have been converted to operational status.

16

METEOSAT 6 (November 1993-June 1996) C

Figure 9.18. The positions of geostationary meteorology satellites. The

ground platforms.

i

(1989)

O GOES 9 (1995)

O

(Nov 1989)

t

(1984)

Eumetsat launched Meteosat 7 under the Meteosat Transition Programme. Two further geographical positions - in addition to the five World Weather Watch positions referred to above — are

Following the launch in 1977, 1981 and 1988 of the first

occupied by the Russian Elektro 1 satellite (at 76° east)

three Meteosat satellites, Eumetsat - established in 1986 —

launched on 31 October 1994 and China’s FengYun 2 satel¬

was given the job of funding the Meteosat Operational Pro¬

lite (at 105° east) launched on 12 June 1997.

Meteorology

120°

100

O

ELEKTRO 1 (31 October 94) • —--

-O

GMS 1 (July 77)

rEOSAT 2 (August 1981) PEOSAT 3 (August 1988 - June 1989)

© INSAT-1 B (October 83-august 93)

il 1990)

rEOSAT 5 (May 1991) i 1997)

1 '»-© (Dec. 81-June 89)

GMS 3 (August 84)

GMS 3 (Dec. 89-June 95) Q

Q IN SAT-1 A (4 September 82)

rEOSAT 4 (June 1989 - January 1990)



GMS 2 (August 81-Sept. 84) GOES 3 (1978)

1990 - Nov. 1990)

180

FENG YUN-2 B (10 June 97)

GOES 1 (1975)

(June 1981 - July 1981)

luary 1990 - April 1990)

160

140

... (July 95)

IN SAT-1 C (July 88-Nov. 89) # • INSAT-1 D (June 90) • IN SAT-2 A (July 92) ® INSAT- 2 B (July 93) • INSAT- 2 C (6 December 95) ® INSAT- 2 D (3 June 97) • INSAT- 2 E (2 April 99)

GMS 4 (Sept. 89) (Dec. 89-June 95)

(june 95) ©---# GMS 5 (March 95)

|

245

246

i

Earth observation

Figure 9.19. Image produced from data acquired using the ‘visible’channel

southwards in Africa and Latin America. The cloud-bands that can be seen at

on Meteosat (4 November 1986). This image, processed by the European

high altitudes are caused by fronts associated with cyclonic conditions. One

Space Agency, took 25 minutes to acquire by a west-to-east sweep;

such front has reached the northerly part of the Western Sahara. The irregular

the scanning motion was obtained by rotation of the satellite (see fig. 9.8a),

cloud masses off the coast of South Africa are the product of condensation

the succession of scanlines being obtained by switching the telescope axis

over cold surface water. The areas of clear sky are due to high atmospheric

from north to south.

pressure, particularly over Europe. Image courtesy of ESA.

The band of cloud over the Atlantic and West Africa at equatorial latitudes corresponds to rising moist air in the intertropical confluence zone. It extends

Remote sensing of terrestrial resources

Remote sensing of terrestrial resources is placed, in the field

value, make available new types of information whose rele¬

of observation, somewhere between the acquisition of

vance to meteorology, geology and cartography soon became

low resolution meteorological data and very high resolution

apparent to the scientists who had access to this classified

military reconnaissance. Satellites designed for the remote

data. But to develop a satellite for civil purposes it was neces¬

sensing of terrestrial resources saw service in space some¬

sary, in the United States, to allay the misgivings of those who

what later than non-geostationary meteorological satellites

were worried that the greater accessibility of information

and benefited from the experience accumulated with them.

would be detrimental to national security and also to per¬

But while this technological debt is very clear, there are

suade potential users to pool their efforts in developing a

marked differences in the way the programmes in the two

joint programme. The very different needs of the various cat¬

areas are structured. Pursued through international coopera¬

egories of user — geologists, geographers, agronomists and

tion, satellite meteorology has much in common with a pub¬

environmental experts - created a great many problems when

lic service, enjoying from the outset very specific users

it came to defining the technical characteristics of the sensors

expressing carefully targeted needs. Remote sensing of ter¬

required and considerably complicated the arrangements for

restrial resources on the other hand found itself for some

managing and commercialising the programmes (fig. 9.20).

time having to make a tool available to users before there was

With the manned space programmes came much greater

any real expression of demand, which in any case was often

opportunity for innovative experiments. Using hardware from

met in part by aerial photography.

the successful Apollo Moon missions, the Skylab flights were

And while the vast majority of sensors used for satellite

used to test various new instruments, such as the sensors mak¬

meteorology encompass a field of view stretching from one

ing up the Earth Resources Experiment Package (EREP). The

limb to the other, the overall field of terrestrial resource remote

Salyut and Mir stations and the Space Shuttle also provided

sensors is limited by an instrument look angle, as is also the

platforms for considerable observation activity. The Shuttle for

case for military reconnaissance sensors. Viewing angles are

example provided an environment for testing Shuttle Imaging

generally narrower for military than for civil applications.

Radars (SIR) and for Spacelab photographic missions involving

In the very earliest years of the space age, the potential con¬

the Metric Camera and the Large Format Camera (fig. 9.21).

tribution which Earth observation from space could make to

The Mir station - which in its basic configuration incorporates

geography was beginning to be perceived. When, looking

a series of high resolution still cameras (Kate 140, Kate 200,

down from low orbit, the astronauts on board the first

KFA 1000, KAP 350 and MKF6 MA) - was able with the arrival

manned spacecraft — such as Vostok, Voskhod, Mercury and

of the Priroda module equipped with passive and active

Gemini — saw with their own eyes the Earth unfold before

remote-sensing instruments to support an operational mission

them, they were struck by the implications of this vision for

specifically devoted to the environment, oceanography and

an understanding of the terrestrial landscape. It was common

atmospheric research.The German sensor MOMS 02 was twice

at that time to talk of‘geographical satellites’. A 1956 report

used in Spacelab, in April 1993 onboard the Space Shuttle and

by the American Academy of Sciences bore the title‘Spacecraft

in 1996 on Priroda (MOMS 02P).

in Geographic Research’ and a study which the same Acad¬

Other experiments were conducted as part of the Heat

emy commissioned from the Office of Naval Research and

Capacity Mapping Mission (HCMM), devoted to fairly fine

NASA in 1965 was called ‘Geography from Space’. And while

resolution thermal infrared imagery, from a number of Kos-

the qualifier ‘geographical’ subsequently came to be used less

mos satellites and above all from Nimbus 7 with its Coastal

frequently, the fact remains that a whole series of satellites are

Zone Colour Scanner (CZCS).

fundamentally important to geography as a whole, even if the

Operational missions in the visible and near infrared, some¬

terminological preference is now to refer to resources, the

times coupled with the thermal infrared, have been conducted

environment or simply ‘Earth observation’.

under a number of automatic satellite programmes. The most

Earth observation was first developed for military purposes

important of these - those which have succeeded in providing

(see chapter 12). In a situation in which international air law

a high level of continuity of image provision and consistent

provided for the sovereignty of states over their airspace, the

user access to the images acquired - are the American Landsat

planetary nature of the movements described by satellites was

programme which began as early as 1972, the French SPOT

recognised as a key to the acquisition of information over

programme which got underway in 1986 and the Japanese

areas hitherto regarded as inaccessible. The first remote¬

MOS and Indian IRS programmes with start dates in 1987 and

sensing images did however, in addition to their strategic

1988 respectively.The trend towards involving more and more

2 47

248

Earth observation

Figure 9.20. Time chart of satellites performing Earth resource remote¬

sensing missions. A number of Russian military reconnaissance satellites

of imaging into the satellite domain. Radar imagery from

and some weather satellites which also perform terrestrial resource missions

space made its debut with the launch on 26 June 1978 of the

have only been shown in the time-charts covering their primary activity. The

American Seasat satellite. The technique used on this and the

Chinese FSW satellites shown here also serve military purposes.

other satellites in the series was that of Synthetic Aperture Radar, which uses the satellite’s motion along its orbit to cre¬

countries is continuing with conventional systems such as the

ate a virtual aperture much wider than the real aperture,

Chinese-Brazilian CBERS satellite, launched in 1999, but also

thereby providing improved resolution (see fig. 9.9c). It is

thanks to the development of simpler and significantly

more commonly referred to by its acronym SAR (fig. 9.22).

cheaper systems derived from the Uosat platform developed

Setting aside its military applications, the main users of

by the University of Surrey; these less complex systems are

radar imagery for the remote sensing of terrestrial resources

intended to allow emerging countries to familiarise them¬

are the Russian Almaz programme, the European ERS satelhtes,

selves, albeit in a limited way, with this type of application.

the Japanese Earth Remote Sensing Satellite (JERS) programme

Progress was rather slower in the radar imaging field.

and the Canadian Radarsat series, although some work has

There still seemed little prospect in the 1960s of being able

also been done from the Space Shuttle and the Priroda module

to fly radar imagers onboard satellites in view of the amount

attached to the Mir space station.

of energy required to receive back a measurable signal, fol¬

SAR systems are becoming more diverse, with the use of a

lowing its emission by the onboard sensor and a ‘round trip’

range of different incidence angles, horizontal or vertical

of more than a thousand miles. Radar as an application

polarisation at reception or emission, and an increasing vari¬

seemed to be restricted to aviation, where it was already in.

ety of bands (see fig. 9.13). The specific features required for

very wide use. Subsequent advances in solar array and radar

particular types of use depend on the surface texture of the

technologies did however make it possible to take this form

areas studied, their vegetation cover and water content.

Remote SENSING OF TERRESTRIAL RESOURCES

Figure 9.21. Photograph taken by the Large Format Camera. This photograph was taken on 8 October 1984, from an altitude of 230 km, on Space Shuttle flight 41G. The image, originally recorded on 23 cm x 46 cm film, covers a ground area 344.67 km in length and 172.33 km in width. It depicts the area round Cape Canaveral in Florida. Another smaller-field image of the same area, supplied by SPOT, is reproduced in part in fig. 5.19. Image courtesy of NASA.

Figure 9.22. Image acquired by X-SAR Synthetic Aperture Radar. This German-ltalian experimental radar sensor was flown on Space Shuttle mission STS 59. It uses the X-band. This image, acquired on 12 April 1994, shows an area of the Algerian Sahara in which small relief features associated with outcrops of resistant strata are partly hidden by sand-stripes without backscatterin the X-band. Image by courtesy of DLR/DPAF.

\

249

Optical remote-sensing systems

The Landsat programme

of developing the sensors went to the Goddard Space Flight

The idea of a civil Earth observation programme began to

Center which already had experience of meteorological and

take shape as early as 1962, prompted by the enthusiasm

geophysical satellites but was new to Earth observation —

with which photographs of the Earth from manned space¬

unlike the Johnson Space Center, which continued to concen¬

craft had been greeted by a very wide audience and also by

trate

the interest generated among scientists having access to clas¬

observers this decision by NASA had one fundamental draw¬

sified data acquired by military reconnaissance satellites. A

back, which was that the Goddard team would be looking to

meteorological satellite programme was seen too as a possi¬

test its new systems rather than giving priority to meeting the

ble framework for experimentation. And yet it would be

requirements of future users. There were other problems too:

post-Apollo

applications. According

to

some

another ten years before the first satellite in the Landsat series

the sometimes conflicting demands of the various partici¬

was lofted. The length of that intervening period suggests

pants in the project, the need to avoid friction with the

how difficult it was, for structural and political reasons, to

Department of Defense and that of complying with national

get from the idea to a system that was up and running.

policy directives, all of which meant specifying technical

The period from 1962 to 1966 was taken up at NASA with study of the various technical options for such a programme.

capabilities that would be acceptable to all concerned in what was a highly sensitive area.

The Department of Defense having refused to declassify the

A programme for the study of Earth resources from auto¬

technologies embodied in its military satellites and with the

matic satellites was in the end approved by the US House of

bulk of NASA’s resources tied up in the manned space pro¬

Representatives in 1969. In keeping with the political deci¬

gramme, it was hardly surprising that thought should first

sion which finally emerged, the programme was presented as

turn to manned spacecraft as a platform for Earth observa¬

an investment which would benefit the whole of mankind.

tion experiments. The NASA laboratories were moreover pri¬

And while the first satellite under the programme was

marily interested in developing new sensor technologies and

initially called ERTS 1 (Earth Resources Technology Satellite),

as this implied relatively long lead times, most of the pro¬

it was later renamed Landsat 1, a designation retained for the

posed projects targeted post-Apollo applications.The reason¬

rest of the series.

ing at that time was that astronauts would need to test a

Landsat 1, 2 and 3, launched from the Yandenberg Space

number of systems before an operational automatic system

Center in 1972, 1975 and 1978 and based on the platform

could be developed. For their part, potential users such as the

used for the Nimbus meteorological satellites, made up an ini¬

Geological Survey tended to favour relatively unsophisticated

tial series within this family of satellites (see fig. 9.20). They

satellites which could be tailored to their requirements and

operated from a circular Sun-synchronous orbit at an altitude

made available in a short space of time. This approach corre¬

of 920 km and effected their descending node pass at 09:30

sponded to NASA’s minimalist option for Earth observation

(fig. 2.27).They had an 18-day orbital cycle (see fig. 3.25).

based on three types of satellite - large, medium and small.

Landsat 4 and 5, launched in 1982 and 1984, again from

The balance of opinion within NASA was weighted towards

Vandenberg, formed a second series. Their orbit, while still

the most complex of these structures.

circular and Sun-synchronous, was now lower at 690 km.

The decision to go ahead with the Landsat programme was in the end taken under pressure from the user agencies, and

250

on

Equator crossing time in the descending pass was 09:37 and the orbital cycle lasted 16 days (see fig. 3.26).

more particularly the Department of Agriculture and the

Although some users, familiar with photointerpretation,

Department of Interior with of course the Geological Survey.

would have liked the Landsat series to have been equipped

The latter, particularly unhappy with the protracted soul-

with photographic cameras, this option was rejected because

searching at NASA, even went so far as to petition Congress

of technical constraints and also as a result of opposition

for funds to launch a satellite which it proposed to develop

from the Pentagon, NASA preferring not to cross swords

itself. And although NASA, by reacting immediately, did suc¬

with it on this issue. The early Landsat craft carried two sen¬

ceed in retaining responsibility for the project, it found itself

sors, the Return Beam Vidicon (RBV) TV camera and the

committed to developing the satellite to a short timescale.

MultiSpectral Scanner (MSS). An RBV camera had earlier seen

Even so, another year passed before an official decision was

service in the Ranger lunar observation programme and, at

taken, in October 1968, on the choice of sensors.The satellite

the time the Landsat instrument payload was being elabo¬

would use existing technologies except in respect of sensors,

rated, a more advanced version was being developed, though

on-board recorders and the data processing system. The task

it had not been assigned any particular mission. The RBV was

Optical REMOTE-SENSING SYSTEMS

Figure 9.23. Multispectral image acquired by the Multi Spectral Scanner

while the bare soil and the low-chlorophyll crops characterising the acquisi¬

(MSS) on Landsat 1. MSS images are made up of pixels each representing a

tion period (February) appear orange-tawny or yellow. A complete MSS scene

56 m x 79 m ground area. This image of the Ganges delta is a false-colour

is a non-rectangular parallelogram (see fig. 3.2) whose base represents 185

composite combining channels 4 (in yellow), 5 (in magenta) and 7 (in cyan).

km on the ground. The rectangular extract reproduced here covers a ground

The waters of the Bay of Bengal are roily, which explains the particularly light

area of 172 km. Image: courtesy of NASA.

blue which prevails. The chlorophyll-rich mangrove forests are shown in red

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251

252

Earth observation

not moreover one of the instruments used by the military.

law on the commercialisation of remote sensing data and, in

Use of the sensor attracted support from the Department of

1985, handed responsibility for the Landsat programme

the Interior but a fair degree of opposition had to be over¬

over to a private entity, the Earth Observation Satellite Cor¬

come on the way to its adoption. Landsat 1 and 2 were

poration (EOSAT). Image archiving was left to the Depart¬

equipped with one version of the RBV, while the third satel¬

ment of Commerce. The US government does however still

lite in that first series carried another model (fig. 9.6 and

find itself subsidising the Landsat programme for want of a

table 9.1). The results were disappointing however and it was

real market.

not kept on for the second Landsat series.

Landsat 6, built for EOSAT under NOAA responsibility,

The other sensor, MSS, was the product of both civil and

was lost on 5 October 1993 during an unsuccessful launch

military research at the University of Michigan. Scientists at

on a Titan II vehicle. The lost satellite had been equipped with

NASA took the view that agricultural studies would benefit

the new Enhanced Thematic Mapper (ETM), featuring six

particularly from this multispectral scanner whereas Earth

bands in the visible, NIR and SWIR ranges offering a spatial

science specialists were concerned at the more limited reso¬

resolution of 30 m, one band in the thermal infrared with a

lution it offered. The Department of Agriculture having put

resolution of about 100 m and lastly a new panchromatic

all its weight behind the effort to get the sensor flown, NASA

band with a resolution of 15 m. It was not until 1998 that

grasped this opportunity to counterbalance the power of the

Landsat 7 was launched. The trend was by this time towards

Department of the Interior. In February 1969 the decision to

achieving savings by pursuing civil and military objectives in

equip the satellites with MSS was taken.

tandem but disagreement between DoD and NASA on the

The MSS carried by the second Landsat series scans a

sensors to be flown was initially something of an obstacle.

185 km wide swath.The MSS scenes acquired by the Landsat

When a decision was taken in 1994, it went in favour of a

family constitute the first near-exhaustive collection cover¬

single sensor, ETM + , prompting a transfer of military fund¬

ing the surface of the Earth’s exposed land masses at various

ing to NASA which had in the meantime become sole prime

seasons (fig. 9.23).

contractor for the satellite. Programme organisation and

The second series was further equipped with a seven-

satellite data management are performed jointly by NASA,

channel radiometer, the thematic mapper (TM), offering

NOAA and the US Geological Survey, part of the Ministry of

improved spatial resolution. TM-acquired scenes are of excel¬

the Environment. The EOSAT corporation, itself bought out

lent quality overall and represent a considerable improve¬

by Lockheed in 1996, now concentrates on commercialising

ment in the precision of remote-sensing scan data.

remote-sensing images.

The two Landsat series differed too in the data transmis¬

The ETM+ sensor draws heavily on its forerunner on

sion modes used. Satellites in the first series either transmit¬

Landsat 6, though with a number of improvements, includ¬

ted data in real time direct to ground receiving stations,

ing resolution enhancement to 60 m in the thermal infrared.

when they were in their line of sight, or recorded it on¬

What the future holds in store after Landsat 7 is only partly

board for subsequent transmission to the ground stations.

clear. There are plans to equip future Landsat craft with an

On-board processing is no longer a feature of satellites in the

Advanced Land Remote Sensing System (ALRSS) and testing

second series. These rely solely on real-time transmission,

of new instruments can be expected under NASA’s New Mil¬

either directly or indirectly via a geostationary relay satellite

lennium Programme, basically a research and development

(TDRSS) which retransmits data received to the White Sands

programme focusing on remote sensing, communications

station in the United States.

and power production. The Earth Orbiting 1 (NMEO ^plat¬

Although the volume of images acquired and their rele¬

form is likely to carry a new-generation Earth Surface Spec-

vance to a wide range of users bear ample witness to the

troradiometer dubbed Advanced Landsat together with an

technical success of the Landsat programme, hesitations as to

Integrated Multispectral Atmospheric Sounder (IMAS). These

its status have placed a continuing question mark over its

developments are in keeping with the broader role which

future. The intention at the outset was that Landsat data

has now been assigned to Landsat in environmental moni¬

should benefit the international community and charging

toring. They also allow civil aims to be tied in with high tech¬

for images distributed was based almost entirely on the costs

nology projects derived from research pursued under the

of reproduction and forwarding. This policy, which was sim¬

Strategic Defense Initiative.

ilar to that adopted for satellite meteorology data, was designed to generate interest among potential users in

The SPOT Programme

advance of a commercial system. As early as 1979 the Carter

The SPOT (Satellite Pour 1’Observation de la Terre, Earth observation

Administration, aware of the NOAA’s experience in the

satellite) programme was approved in 1978 by the French

management of weather satellites, gave it temporary respon¬

government, with Belgium and Sweden-as minority part¬

sibility for operating the Landsat system as a step towards its

ners. A proposal to establish this second satellite system

eventual privatisation. Despite continuing debate as to.

for permanent observation of the Earth had previously

whether the Landsat system could be run profitably, Con¬

been submitted to the European Space Agency but had not

gress adopted in 1984, while Ronald Reagan was in office, a

gained acceptance.

OPTICAL REMOTE-SENSING SYSTEMS

Figure 9.24. Image of Paris acquired by SPOT 5 (HRG Supermode) on 16 May 2002. © CNES 2002 Distribution Spotlmage.

!

253

254

i

Earth observation

Figure 9.25. SPOT Grid Reference System (GRS). The geographical number¬

oblique-viewing corridor straddling ground track N 19 appears in darker.

ing (N series) of the ground tracks applies to the 369 tracks which make up

green. Scenes obtained by oblique viewing are always centred on a J-series

the complete orbital cycle. They are numbered from east to west starting

line but their centre may deviate in longitude from the GRS nodal point.

from track N1 which crosses the Equator at 29° 36 east. The chronological

The figure shows for J 264 two scenes acquired by vertical viewing with

numbering (R series) of the tracks applies to the 369 tracks in order of over¬

twinned sensors during a pass along N 19. These scenes can be referenced

pass (see fig. 3.26). The observation swaths, relating to twin-HRV vertical

as K 37 and K 38 on J 264.

viewing, are numbered geographically in the K series. As each ground track is associated with a series of scene pairs, each track in the N series is bordered

Figure 9.26. Panoramic image derived from SPOT stereopairs. This

by two scenes referenced by K values equal to 2N in the east and 2N-1 in the

panoramic view of Reunion Island was obtained from SPOT images acquired

west. The lines in the J series are parallels of latitude. The 950 km wide

between 1986 and 1993. SPOT images © ONES 1986-1993, distributed by SPOT Image, produced by ISTAR.

Piton de la Fournaise Piton des Neiges

La Pointe des Galets

Optical REMOTE-SENSING SYSTEMS

150

120

120'

I

150

Kiruna Arctic circl

Ramstein (Eagle Vision) Prince Albert Obninsk £i Gatineau Q Islamabad

.Taejon Maspalom;

Singapoi

Cotopaxi

irepare

Cuiaba Hartebeesthoek 9 Cordoba

Hobart

Antarctic circle

Figure 9.27. SPOT receiving stations in 2002. Eagle Vision is a prototype mobile receiving station being tested by Matra. It comprises a 3.6 m

The basic concept was to treat remote sensing as a com¬ mercial endeavour rather than as a scientific activity, as had

antenna and two trailers. This system is suitable for operation with all commercial satellites.

been the case with a number of programmes (Landsat, ERS, MOS) at their inception. The decision to offer better resolu¬

gramme, again demonstrating a willingness to look for new,

tion than the Landsat systems was thus driven in part by a

untried solutions. The existence of two utilisation environ¬

desire to enter the international market with a higher perfor¬

ments for space systems is potentially of economic interest

mance offering. The same thinking prompted the creation of

since many elements, including the platform, are capable of

Spotlmage, a private law subsidiary of CNES, a move which

‘dual use’. But adopting such an approach does at the same

had the further advantage of giving CNES responsibility for a

time imply a penalty in terms of adaptability. In the case of

national programme clearly distinct from the programmes

the SPOT 4/Helios 1 pair, the advantages outweighed the

pursued cooperatively in an ESA framework. The need for

disadvantages, particularly as the aim on the military side

public support in the early stages was nevertheless clearly

was to acquire an initial capability, which gave the design

recognised from the outset since the initial funding alloca¬

authority a reasonable degree of freedom. With the military

tion covered the cost of developing and launching the first

developing its own expertise and hence an ability to elabo¬

two satellites in the series. But it was not until 1990 and the

rate more precise requirements and with the growing

decision on funding of SPOT 3 that the commercial viability

emphasis on the flexibility needed to adapt to emerging civil

of the SPOT programme was officially called into question.

requirements, it seems likely that the joint approach will

SPOT was however already demonstrably an operational pro¬

produce more limited benefits when the programme moves

gramme and this contrasted sharply with the vagaries of

on to SPOT 5/Helios 2.

American policy on the status of Landsat. The diplomatic

SPOT satellites move in a circular, sun-synchronous orbit at

benefit to France of possessing the only commercial system

an altitude of 830 km. They effect the descending node pass

in existence was seen as justifying continued investment.

at 10:30 and have a 26-day orbital cycle (see fig. 3.26).

The SPOT programme took a further step forward with

SPOT 1, 2 and 3 each carry a High Resolution Visible (HRV)

the successful launch of SPOT 4 in March 1998. SPOT 5 was

instrument based on linear array sensors (fig. 9.8d). The

launched in May 2002. The SPOT follow-up system known

sensors can operate in two modes. In panchromatic (P) mode

as Pleiades is under active discussion. This involves a constel¬

the spectral response band is fairly wide (0.51

ptm to

lation of smaller satellites designed to meet national require¬

0.73 |xm) but the ground area represented by individual

ments, possibly with a dual approach, and to be developed in

pixels is small (10 m x 10 m on the ground). The multiband

synergy with the Italian COSMO-Skymed program.

(XS) mode comprises three narrower spectral bands (XS1:

The decision to proceed simultaneously with develop¬

0.50 |xm-0.59 |xm, XS2: 0.61

p.m-0.68 pun and XS3:

ment of the civil SPOT satellites and the Helios defence

0.79 p,m-0.89 p,m) but the ground area represented by each

satellites marked something of a turning point in the pro-

pixel is four times as large at 20 m x 20 m. Extracts from diese

255

256

S

Earth observation

images are shown in figures 6.7, 6.9, 6.19, 6.21, 6.30, 6.42

MOS (Momo)

and 6.45. Data acquired in the two modes can also be com¬

Japan’s first remote-sensing programme combines, in a char- ■

bined to form multiple resolution images (see fig. 9.15), ally¬

acteristically innovative approach, development of internal

ing the planimetric accuracy of the XP mode with the fuller

capabilities and, like the other major space powers, participa¬

spectral signature derived from XS data.

tion in Earth observation on a global basis. The main features

A particularly novel feature of the SPOT system is the abil¬

of MOS, and indeed of the JERS programme, reflect Japanese

ity to perform oblique viewing on either side of the satellite

interest in management of planet Earth, from global environ¬

nadir by remotely controlled repositioning of the HRY tele¬

ment issues to the monitoring of major risks, together with a

scope entrance mirror. Scenes can thus be acquired in a cor¬

concern to establish technical credibility at international

ridor 950 km wide (fig. 9.25).This feature offers a number

level. As with its other space programmes, NASDA’s first steps

of advantages, such as the ability to make better use of good

in remote sensing took the form of extensive cooperation

local meteorological conditions or again more flexible

with the United States, one aspect of which was to reutilise

observation of events at optimum dates: crop development

various technologies under US licence, with the gradual

stages, volcanic eruptions, flooding, fires etc.

introduction of improvements as national expertise grew.

This capability can again be exploited to acquire stereo¬

The scientific nature of the programme was at the same time

scopic image pairs of one and the same scene taken at differ¬

emphasised to prevent any disputes arising with the United

ent angles on successive days. It is also possible to reconstitute

States under the “Super 301” agreement governing the liber¬

landforms using photogrammetry techniques and to obtain

alisation of US-Japanese commercial relations.

digital elevation models giving a three-dimensional vision of the terrain (fig. 9.26 and 9.27).

The Japanese satellites MOS 1 and MOS 1 b (Marine Obser¬ vation Satellite) — subsequently renamed Momo 1 and lb,

SPOT 4 is the first of a new generation of SPOT satellites to

Momo meaning peach blossom - have circular, sun-syn¬

be built around a new platform MK2 which allows for an

chronous orbits at an altitude of 910 km and with a 17-day

expanded payload and extended operational life. The HRVIR

orbital cycle, 237 orbits being completed in that time.

instrument operates in four spectral bands: B1 (0.5 |xm—0.6 |xm),B2 (0.61 pim-0.68 |xm),B3 (0.78 pun-0.89 pun) and

The satellites carry three systems: ■ the Multispectral Electronic Self-Scanning Radiometer

short-wave infrared (1.58 pum—1.75 pun), offering ground

(MESSR) which collects data in four spectral bands simi¬

resolution of 20 m. In addition, the M-band, with ground

lar to the Landsat MSS response bands; ground resolution

resolution of 10 m, covers the same part of the spectrum as

is 50 m (fig. 9.28).The electronic scanning capability

B2 (0.61 pun-0.68 pun).

is shared with the SPOT HRV instrument. The MESSR

SPOT 4 is further equipped with a four-channel ‘vegetation’ instrument,

three

of

the

channels

being

responsive

to the same spectral bands as the HRVIR instrument: B2 (0.61 pm-0.69 pm), B3 (0.78 pm-0.89 pun) and short¬

comprises two sensors, each observing a strip 100 km wide, with 15 km overlap, giving a total swath width of 100 km + 100 km - 1 5 km = 185 km. ■ the Visible and Thermal Infrared Radiometer (VTIR),

wave infrared (1.58 pun—1.75 pm), the fourth being respon¬

which scans a 1500 km wide swath using a rotating mir¬

sive to blue: B0 (0.43-0.47 pm).The vegetation instrument

ror mechanism. One spectral band corresponds to the vis¬

offers much cruder resolving power: 1150m but with a much

ible portion of the spectrum, the other three to the

wider field of view (2200 km), enabling virtually the entire

infrared range: the 6 pun-7 pun band for the study of

surface of the globe to be covered daily. This system is thus

stratospheric water vapour; the 10.5 pun— 11.5 pun and

extremely well suited to the task of monitoring the continen¬

11.5 pim-12.5 pun bands for thermography of the Earth

tal biosphere and crops around the planet (see fig. 9.43).

and its cloud cover.

SPOT 5 provides higher ground resolution: 5 m and 2.5 m

■ the Microwave Scanning Radiometer (MSR), which

in panchromatic mode (fig. 9.24) and 10 m in multispectral

measures water vapour, snow and ice quantities across a

mode across all three spectral bands in the visible and near

3 17 km ground strip.

infrared. The spectral band in the short-wave infrared band is maintained at a resolution of 20 m due to technical con¬

The IRS programme

straints. Its instrumentation is also likely to include an inde¬

India’s resolve to develop a national Earth observation capa¬

pendent High Resolution Stereoscopic (HRS) system with a

bility was first asserted in the late 1970s with the launch in

forward/backward viewing capability and resolution of 10 m.

1979 of Bhaskara 1, followed in 1981 by Bhaskara 2. A far

The philosophy underlying the system is the continuity

more ambitious programme followed as from 1988 in the

and improvement of SPOT products. However, it confirms the

shape of the Indian Remote Sensing (IRS) satellite series

current trend towards smaller and cheaper satellites providing

devoted not only to environmental research but also to land

metre resolution images. In this respect, the new system

and oceanographic applications.

Pleiades will have a very high resolution capability, allowing it •

The originality of the Indian approach resides in the prior¬

to compete with the new commercial systems and may be a

ity assigned to domestic requirements, and in particular more

constellation of smaller satellites.

effective land use through improved general cartography and

Optical REMOTE-SENSING SYSTEMS

Figure 9.28. Mosaic of images acquired by the Momo 1 satellite. This mosaic, built up from four images acquired by the MESSR sensor on 3 and 20 December 1987, depicts Tokyo Bay and the surrounding area. Image courtesy of NASDA.

I

257

258

Earth observation

Figure 9.29. IRS receiving stations in 2002.

improved monitoring of major risks. Here was a situation in

A second satellite with similar specifications, IRS ID, was

which space capabilities were in harmony with land use

launched on 29 September 1997 (fig. 9.30).

management priorities in a developing sub-continent. As has

IRS P3, launched in March 1996 on an Indian PSLV vehicle

been the case across the entire Indian space programme, the

into sun-synchronous orbit at an altitude of 820 km, is pur¬

approach chosen was that of encouraging technology trans¬

suing a range of environmental missions, including the

fers and engaging in wide-ranging cooperative projects with

study of chlorophyll concentrations in seawater, vegetation

the various space powers.

indices, cloud cover investigations and geological cartogra¬

IRS 1 A, launched in 1988 aboard a Soviet rocket, occupied

phy. The sensors equipping the satellite are designed more

a sun-synchronous orbit at an altitude of 900 km. It had a

for spectral than spatial resolution. Like IRS 1C it features a

22-day orbital cycle and executed the descending node pass

WiFS, though with an additional sensor in the 1.5 |xm—

at 10:25. It was equipped with the LISS 1 and LISS 2 (Linear

1.7 |xm band, and its instrumentation also includes an

Imaging Self Scanning) instruments collecting data in four

18-channel Modular Opto-electronic Scanner (MOS) pro¬

spectral bands. A follow-on satellite having the same charac¬

viding resolutions between 580 m and 2520 m. The next

teristics, IRS IB, was launched in 1991.

satellite in the series, IRS P4, carrying an Ocean Colour Mon¬

The LISS 2 equipped IRS P2 satellite, placed in orbit by an Indian PSLV launcher in 1994, occupied a sun-synchronous orbit at an altitude of 817 km, with a descending node pass at about 10:40 and a 24-day orbital cycle.

itor (OCM) sensor covering 9 spectral bands, was launched on 25 May 1999. Where optical imagery is concerned, the Indian remote¬ sensing programme is now emerging as the most ambitious

IRS 1C, lofted by a Russian launch vehicle in December

of the government programmes being pursued by the vari¬

1995, took civil remote sensing substantially further down

ous space powers. No less than three satellites are currendy

the road towards higher resolving powers, almost ten years

scheduled for launch, one devoted primarily to oceanogra¬

on from a similar major contribution by the first SPOT satel¬

phy. IRS P5 and IRS P6 will pursue complementary missions.

lite. This it was able to do thanks to the PAN sensor, which

Assigned to agricultural applications, IRS P6 will carry a

offered ground resolution of about 5 m in a panchromatic

multispectral ‘vegetation’ sensor with 10 m resolution. IRS

spectral band (0.50 (xm-0.75 pjn). Other lower resolution

P5 will be used for cartographic purposes, with 2.5 m reso¬

sensors - LISS 3 and the Wide Field Sensor (WiFS) — also

lution or even better. Launch in around 2003 of Carto-Sat, a

formed part of the instrument payload.

satellite with a resolution understood to be as high as 1 m, is

IRS data are received by India’s Shadnagar station but also

also planned. In choosing to operate two separate systems

by stations around the world (fig. 9.29). They are commer- - side-by-side, the main consideration for India was no doubt cialised in conjunction with Space Imaging-Eosat, already

the need to keep within the launch capabilities of its

responsible for the commercial distribution of Landsat data.

PSLV vehicles, giving it full autonomy in the conduct of its

Optical REMOTE-SENSING SYSTEMS

Figure 9.30. Image acquired by the PAN sensor on IRS ID. The image shows part of the township of Mumbai'in India. Courtesy of NRSA, India.

observation programme. But this approach had the added

mercial market, fully vindicating the policy of commerciali¬

advantage of greatly increasing the number of information

sation by Space Imaging-Eosat. Nor is it by any means

sources and extending coverage.

inconceivable that future satellites could also be used for

In addition to meeting domestic demand, India is looking

military purposes, a policy development which would not

to serve the Asian market, which is predicted to grow

in principle be at odds with the civil nature of the Indian

rapidly. Attractive prices and finer resolution than its rivals

space programme insofar as such military users would be

have allowed IRS 1C to make a successful entry in the com¬

regarded simply as customers.

|

259

260

Earth observation

The Resurs system

part to the unresponsive nature of the commercial structures

The Resurs system is built around two families of satellites,

involved and in part to the increasingly tough competition at *

Resurs F and Resurs O, which are seen as offering a comple¬

international level, leaving little prospect of establishing an

mentary range of capabilities for Earth resource surveying

adequate alternative source of funding. Manufactured by

purposes. Resurs satellites have to date been limited to pas¬

TsSKB (or OKB Koslov) of Samara, the Resurs F satellites can

sive remote sensing. The programme, which came into being

be traced back to the earlier Vostok craft and are close rela¬

in the heyday of Soviet space power, is now having to con¬

tives of the Kosmos reconnaissance satellites (see chapter

tend with drastically reduced funding and consequent

12). They occupy low circular orbits at altitudes between

uncertainty as to its future prospects. Commercialisation of

250 km and 350 km and have a short operational life. The

Resurs products is also proving extremely difficult, due in

altitude at which they fly can if required be lowered to below

Figure 9.31. Extract from a KVR 1000 image. This photograph of the Baghdad

of Resurs satellites are those of third-generation military

region was taken by a KVR camera onboard a Russian Yantar Kometa military

reconnaissance satellites (see fig. 12.1) but some of their

reconnaissance satellite. The Baghdad urban area can be seen in consider¬

products are used for civil purposes, particularly by the

able detail on the left bank of the Tigris. The extract shown here covers a

authorities responsible for cartography. This trend has

ground area 18.6 km wide and 16 km long. KVR 1000 image. Processed by

become increasingly marked with the fall-off in funding and

200 km to give better resolution. The general characteristics

Sovinformsputnik. Distributed by SPOT Image.

OPTICAL REMOTE-SENSING SYSTEMS I 261

the growing need to find commercial outlets in order to maintain the system’s capabilities. The first operational satellite in the Resurs FI series was launched in 1986 and this was followed by many others. Resurs F1 satellites have an average mission duration of only two weeks, compared with a standard one month in orbit for the F2 series, extendable to up to one-and-a-half months. A Resurs F3 version modelled closely on FI but operating at a lower altitude was used on a few occasions in 1993. These satellites are equipped with still cameras (Kate 200 and KFA 1000 for Resurs FI, MK 4 for F2) providing spatial resolutions between 15 m and 5 m; the KFA 3000 camera on-board Resurs F3 gave up to 2 m resolution. In conjunc¬ tion with stellar viewing techniques, the multiband pho¬ tographs taken by these satellites (fig. 9.31) allow for precise geographical position determination of certain images of the Earth. Exposures are returned to Earth in recoverable cap¬ sules. The greatest strength of the photographic equipment carried by Resurs F craft is its very high spatial resolution. The F1M enhanced version scheduled for 1994 did not in the end make its debut until November 1997. Further improved F2M versions were to have come into service beginning 1997 but launch has had to be postponed owing to funding difficulties. The launch on 17 February 1998 of a Kosmos satellite of theYantar Kometa class marked a new departure in the fund¬

images. The Swedish station at Kiruna — which also receives SPOT images — is equipped to receive some Resurs O data and the European company Eurimage also possesses a data collection of commercial interest. Resurs Ol N4 was placed in orbit on 10 July 1998 and will be followed in the next few years by Resurs Ol N5. These satellites feature a number of new sensors, some from Belgium, Germany and Italy, but this is still essentially a mul¬ timission platform. The first of the new generation Resurs DK family devel¬ oped by TsSKB of Samara is scheduled to be launched in 2003. But although the programme was given priority status by the Russian Space Agency in 1996, it remains chronically underfunded, partly as a result of the very small overall space budget and also because what little funds are available have for a long time now been almost entirely eaten up by the international space station programme. The initial project, a fairly ambitious one, underwent some descoping in 1997 to bring it into line with a shrink¬ ing budget but - despite assurances that the technical specifi¬ cations were now final - funding continued to be a problem. Later in the same year the project had therefore to be simpli¬ fied yet further, the Director-General of the Russian Space Agency at the same time announcing that the programme had priority status for both civil and military requirements. Weighing in at 7 tonnes, the satellite will operate from an altitude of between 400 km and 600 km, extending its ser¬

ing and commercialisation of this type of system. This was the first of four missions in a joint venture by the Russian Sovinformsputnik organisation, which is responsible for commer¬ cialising Russian space products, and the American Aerial Images Inc., a specialist in the development of advanced digi¬ tal imagery. The aim is to provide ‘SPIN 2’ imagery covering the world’s main capitals and most towns with more than 50 000 inhabitants.Two cameras, a KVR 1000 with 2 m reso¬

AD EOS

lution and aTK 350 with 10 m resolution, provide 160 km x 40 km and 300 km x 200 km images respectively. A single TK 350 image thus covers the same area as seven KVR 1000 images and the system also has stereoscopic capability. The Resurs O satellites use the same platform as the Meteor 3 series. The first operational flight unit, bearing the name Kosmos 1939, was launched in 1988. Resurs O satellites operate from orbital altitudes of between 600 km and 700 km and are fitted with multispectral sensors similar in many ways to those equipping the Landsat series. They are used primarily for coastal waters surveillance, detection of industrial pollu¬ tion sources and agricultural monitoring. Resurs O satellites have an operational life of 3 to 5 years. Launched in November 1994, Resurs 01 N3 was the first satellite in the series.The first of its two scanners, MSU SK, operates in spectral regions rang¬ ing from the visible (0.5 pm—1.1 pm with resolutions of about 170 m) to the thermal infrared (600 m resolution), while the second, MSU E, covers the visible and the near infrared with 45 m resolution. Resurs O data is commercialised by the Russian consor¬ tium Sovzond, whose offering includes current and archived

Japan’s ADEOS 1 (Advanced Earth Observation Satellite) was launched on 11 August 1996 but contact with the craft was lost on 30 June 1997 with only 20% of the data collection mission completed. This failure has been traced back to structural damage to the solar array paddle. It was placed in a sun-synchronous orbit at an altitude of 797 km, with a descending node pass at 10:30 and a 41-day orbital cycle. It carried a substantial and varied instrument payload. The Advanced Visible Near Infrared Radiometer (AVNIR) operated in the visible (0.42 pm0.50 |xm, 0.52 pm-0.60 pm, 0.61 pm-0.69 pm) and the near infrared (0.76 pm-0.89 pm) at 16 m resolution and in a panchromatic band (0.52 pm—0.69 pm) at 8 m resolution across an 80 km strip width (fig. 9.32). The Ocean Colour and Temperature Scanner (OCTS) delivered poorer spatial resolution (700 m) and greater (1400 km) strip width but had finer spectral resolving power in the visible (0.402 pm0.422 pm, 0.433 pm-0.453 pm, 0.479 pm-0.500 pm, 0.511 pm-0.529 pm, 0.555 pm-0.575 pm, 0.660 pm0.680 pm), the near infrared (0.745 pm-0.785 pm, 0.845 pm-0.885 pm), the short-wave infrared (3.55 pm-

vice life to 3 years. In panchromatic imaging mode it is expected to provide 1 m resolution, this being the minimum currently imposed by the Russian government, with resolu¬ tions of 2-3 m in multispectral mode and 6-8 m in the near infrared waveband.

262

'

Earth observation

Figure 9.32. Multispectral image acquired bytheAVNIR sensor on ADEOS1. The image shows the same region (Department of Iwate, Japan) as that

Sensing System (NROSS) programme (the latter cancelled

appearing in fig. 9.39. © NASDA.

in 1988); and a Total Ozone Mapping Scatterometer (TOMS). The

CNES-supplied

Polarisation/Directionality

of Earth

Reflectance (POLDER) sensor collected data over a 1440 km x 1920 km area, which meant that a specified region could 3.88 |xm) and the thermal infrared (8.25 |xm-8.80 pan,

be observed from different angles in successive passes. Mea¬

10.3 pm-11.4 |xm, 11.4 |Jtm-l 2.7 |xm). A number of these

surements were taken in eight spectral bands in the visible

wavebands are particularly well suited to the study of matter

and near infrared in natural and polarised light. The data

contained in seawater and more particularly chlorophyll dis¬

gathered in this way will contribute to a better understand¬

tributions. OCTS readings were moreover obtained using a

ing of the directional properties of solar radiation reflected

rotating scanner and the resulting oblique viewing angles

by the Earth and the atmosphere.

allowed most specular reflection of solar rays off the ocean

A second satellite in the series, ADEOS 2, is to be launched

surface to be avoided. NASA supplied two instruments: an

in 2002 and will operate from a similar orbit to its forerun¬

NSCAT scatterometer derived from the Seasat model but

ner. ADEOS 2 will carry sensors developed by NASDA, one of

improved for the US Navy as part of the Navy Remote Ocean

which will be an advanced microwave radiometer (AMSR).

Optical REMOTE-SENSING SYSTEMS

I

Seostor

lution while the high resolution CCD camera, which has some

The OrbView 2 or Seastar satellite from the firm Orbimage

limited stereoscopic capability, is able to supply images with

was launched in August 1997. It is equipped with SeaWiFS,

20 m resolution in five spectral bands. Phenomena detected in

an eight-channel sensor covering a spectral range from 402

wide view by the WFI can thus be ‘zoomed’ by the CCD

nm to 885 nm. Data collected is used to determine chloro¬

though with a time lag of up to three days. Lastly the Infrared

phyll, humic substance and sedimentation levels in the

Multispectral Scanner (IRMSS) operates in four spectral bands,

oceans and inland lakes and the concentration of atmos¬

imaging a 120 km swath with a resolution of 80 m. The last

pheric aerosols, the latter information providing a basis for

two sensors provide complete Earth coverage in a 26-day cycle.

signal correction decisions. OrbView 2 imagery also covers

The form commercialisation policy will take would still

land-based vegetation. Its 2800 km swath is sufficient for full

seem to be undecided. Judging by approaches made to West¬

daily coverage of the Earth’s surface and colour imagery from

ern firms concerning a high resolution sensor, it seems likely

the satellite is continuously downlinked in real time and can

however that improved resolution will be a feature of the

be acquired by HRPT ground stations.

new satellites. Independently of future CBERS, China is also pursuing a

UoSat

different programme known as ZY 2. Commercialisation is

The UoSat series of small satellites are designed and built by

not a priority in itself but rather expresses the need for the

Surrey Satellite Technology Ltd. (SSTL), a company set up in

two countries to develop their territories.

1985 by the University of Surrey to support technology transfer

to

industry

and

commercial

development

of

Ikonos

research activity. The UoSat series is also used to test satellite

Following a series of failures - Early Bird, Lewis and the first

miniaturisation. A number of these mini-satellites

are

Ikonos satellite - and the decision not to proceed with Clark,

equipped with various remote-sensing instruments, often

very high resolution commercial remote sensing got under¬

with low spatial resolution, examples being Kitsat, a joint

way in earnest with the successful launch by Space Imaging,

project with South Korea (1992) and Posat, in association

of Ikonos 2 on 24 September 1999 (Fig. 9.33).

with Portugal (1993). The most powerful satellite in the

Ikonos marked an important new departure in two respects:

series is the 325 kg UoSat 12, a cooperative venture with

the resolution offered and reliance on private funding. Lock¬

the University of Singapore, launched from Baikonur on

heed Martin, the largest American space enterprise, was devel¬

21 April 1999. It carries a four-band multispectral sensor

oping plans for a commercial remote-sensing system as early

with 32m resolution and a 10 m resolution panchromatic

as 1991 and in June 1993 it applied for a licence covering

sensor. The scenes generated cover ground areas of 3 3 km x

images with 1 m resolution. That request was granted the fol¬

3 3 km and 10 km x 10 km respectively.

lowing April by the US Department of Commerce in pur¬

CBERS, ZY2

in December 1994 to the creation of Space Imaging by Lock¬

The CBERS (China Brazil Earth Resources Satellite) programme

heed Martin, Raytheon’s E Systems and Mitsubishi. With Lock¬

is a fine example of creative cooperation by China and Brazil in

heed’s buy-out of Hughes’ shares in Eosat, the company -

suance of the presidential directive of 23 March 19 94. This led

the development of two satellites in the Landsat category.

which with its new affiliate became Space Imaging Eosat -

Approved in 1988, the programme brought China external

went on to acquire a complete end-to-end capability. Current

funding for development, manufacture and launch of the ini¬

estimates suggest the overall cost of the Space Imaging opera¬

tial satellite. The programme was also for China a fast route to a

tion (2 satellites, 2 launchers, 1 primary and 2 secondary sta¬

civil satellite with a 2-year design life — which contrasts

tions, plus imaging hardware and software) may amount to

favourably with the short observation times available on FSW

some $500 M, equivalent to about a year’s income.The com¬

capsules. For Brazil the agreement was part of a broader policy

pany’s strategy would seem to be to fully exploit its technical

aimed at introducing Brazilian high-technology products to

superiority and financial strength while encouraging regional

the Chinese market and was also a means of diversifying coop¬

franchises, such as the one granted Mitsubishi.

erative links in satellite imagery, a major priority for the Brazil¬

Operating from a sun-synchronous circular orbit at an alti¬

ian space programme since 1978.The programme was to have

tude of 681 km, the satellite is supplying images in panchro¬

been operational by 1993 but, owing to delays in Brazilian

matic mode (0.45 pm—0.90 pm) with resolution varying

funding, CBERS 1 did not in fact reach orbit until October

from 0.82 m at nadir to 1 m and 1.12 m up to 26° and 45°

1999. A follow-up satellite is to be launched, with integration

respectively either side of nadir. It also provides multispectral

likely to be performed in Brazil, and discussions are continu¬

images with resolutions of3.2mto8mina range of bands

ing on the construction of two further units, CBERS 3 and 4.

also used by Landsat: 0.45 pm-0.52 pm, 0.52 pm-0.60 pm,

The CBERS series is unusual for its ability to provide global coverage with its multi-sensor payload combined with a high

0.63 pm-0.69 pm, 0.76 pm-0.90 pm. Strip width is limited to 13 km.

revisit frequency. The Wide Field Imager (WFI) provides a syn¬

Revisit capability using one satellite only is 3.9 days for

optic view of the Earth every five days with 260 m spatial reso¬

1 m resolution in panchromatic mode and 4m in multispec-

263

264

I

Earth observation

Figure 9.33. First image acquired by the lkonos-2A satellite. This metrerange resolution image depicts downtown Washington; the Washington Mon¬

tral mode; for 0.82 m resolution, the revisit figure is 11 days.

ument and the Ellipse can be made out on the left and, on the right, the

When a satellite pair is available, a 3.2 day capability will be

National Museum of American History and the Department of Commerce

achieved, and even a single day in regions at 51° latitude.

complex. © Space Imaging.

Finally, the satellite offers very flexible data collection since final programming can be performed up to a few minutes before the satellite pass.

EROS

Ikonos data is forwarded by the Norman Station in Okla¬

The launch of the Israeli satellite EROS A1 by the Russian

homa (USA) to a number of stations around the world:

launch vehicle Start 1 in December 2000 signalled the arrival

Shadnagar (India), Dubai (United Arab Emirates), Neustrelitz

of a new player in the market for one metre resolution

(Germany) and Chung-Li (Taiwan). A limitation was however

imagery. The 250 kg satellite follows a circular orbit at altitude

placed on universal distribution of 1 m resolution images

480 km and provides a resolution of 1.8 m in panchromatic

when the US Congress voted in 1996 to outlaw the distribu.-

mode and 0.8 m using an oversampling technique (fig. 9.34).

tion of images of Israel where these were of higher resolution

It constitutes the first element in a constellation comprising at

than those available from international competitors.

least two EROS A satellites, the second being scheduled for

Optical remote-sensing systems

!

launch in 2002, and six EROS B satellites to be launched over

tion, which places their requests first among those submit¬

the next five years. Given the agility of the system, a single

ted by AAD partners. PAS partners' requests go to the top of

satellite provides a mean revisiting time of 1.8 days, descend¬

the list of images to be acquired by the next available satellite.

ing to 1.1 days with two satellites, whilst six satellites will be

Conflicts between two geographically adjacent PAS partners

able to cover every point of the globe at least once a day and

are mediated on a first-come, first-served basis, for the most

eight satellites will allow revisitation more than twice daily.

timely response, with a delivery time of 48 hours before the

Although this is a civilian programme, Israel is using

image is made available. The most original type of partner¬

experience gained in the field of military reconnaissance.

ship is the third, whereby the customer can hold exclusive

Indeed, one aim is to obtain some financial return on devel¬

rights to images produced by a given satellite over a zone of

opment of the military Offeq satellite. The company respon¬

radius 2000 kilometres around the ground receiving station.

sible for marketing is ImageSat, with headquarters in Cyprus

This station with both uplink and downlink capabilities is

but largely run from Tel Aviv. It is a joint venture between

supplied by ImageSat as part of the SOP program. It allows

Israeli companies IAI and ELOP, and the US company Core

the customer to control which angles are viewed by the satel¬

Software Technology. The marketing policy favours sale of

lite as soon as it flies into the relevant coverage zone. The

images to government bodies within the framework of

satellite then downlinks the required images exclusively to

specifically drawn contracts known as SOPs (Satellite Operat¬

the SOP customer. ImageSat insists that there is no possibility

ing Partnerships). Technical specifications are designed to

of conflicting orders in the same zone since by definition

meet civilian as well as security needs, including urban plan¬

only one country can have an SOP in a given zone. It would

ning and development of the oil and gas industries. Data

only be by increasing the number of satellites that several

from space is intended to complement aerial photography

countries might access the same zone via different satellites.

products. This explains the 50 cm resolution planned for

The Israeli Ministry of Defence is supposed to pay Image¬

EROS B, which may actually be launched in preference to

Sat International about $ 15 million for the exclusive rights to

EROS A1 if market requirements should justify it.

all photographs of Israeli territory taken by the EROS 1 civil¬

EROS data can be acquired via three main channels: acqui¬

ian satellite.The exclusive receiving rights, signed on 3 Janu¬

sition, archiving and distribution (AAD), priority acquisi¬

ary 2001, include not only Israeli territory, but also the area

tion service (PAS), and satellite operating partnership (SOP).

within a 2000 km radius.The region extends to Libya in the

The so-called AAD system is currently based on thirteen relay

west, Sudan in the south, the Gulf of Oman in the east, and

stations which can downlink, store and forward data. These

CIS countries in the north. The entire territory of Iraq, Iran

are set up in South Africa, Argentina, South Korea, Italy,

and Syria is included within the area, as well as almost all of

Japan, Russia, Singapore, Sweden, Taiwan, the United States,

Libya, most of Sudan and the Muslim republics of the former

Norway and Canada. The second option can be exercised by

Soviet Union.

any customer within the bounds of existing SOPs. Priority

The success of the EROS programme thus directly depends

acquisition service partners have priority in satellite tasking.

on the interest shown by government bodies and the num¬

Partners submit image requests to the ground control sta¬

ber of SOPs purchased.

Figure 9.34. Image of

Izmir acquired by EROS Al© ImageSat.

265

SAR-equipped Earth resource systems

Seasat

procedure with military satellites. With a total propellant

The American Seasat 1, launched on 26 June 1978, was the

load of 1350 kg and routine consumption of only 100 g a

first satellite designed for remote sensing of the Earth’s sur¬

day, a substantial reserve was available and this was primarily

face using synthetic aperture radar. By the time it ceased

used for such orbit manoeuvres.

functioning on 10 October the same year it had sent back

Almaz 1 was equipped with an HH-polarised SAR operat¬

images covering 125 million km2 of territory in North

ing in the X-band and two antennas, one left-pointing, the

America, Western Europe, the North Pacific region, the arctic

other right-pointing. The SAR’s incidence angle could be

zones and the North Atlantic. Seasat paved the way for many

adjusted within a 30° to 60° range either side of nadir. Reso¬

other programmes.

lution was about 15 m. Almaz data was commercialised by

The Seasat SAR, equipped with a single rightward-point¬

the American Space Commerce Corp., by Almaz Corp. and by

ing radar antenna, offered little flexibility, there being no

other distributors such as Hughes STX. Whether the launch

scope for modifying its wavelength (L-band = 23 cm), inci¬

of Almaz IB, with a more varied payload thought to include

dence angle (20° nadir deviation) or HH polarisation.

two SARs, eventually materialises will depend on whether

Despite this shortcoming, the scientific results obtained were

the US-Russian company Sokol Almaz Radar manages to

of the greatest importance, demonstrating in particular the

secure the necessary funding.

relevance of SAR imagery to the study of ocean swell direc¬ tions, the surface manifestations of internal waves, topo¬

The ERS, Envisat programme

graphic gradients, ground surface roughness and geological

The European Space Agency’s European Remote Sensing

structures (see fig. 9.37).

satellite (ERS) programme was given the go-ahead in 1982

Seasat carried a number of other instruments, including a

by the Agency’s then 12 member states and Canada. The deci¬

radar altimeter used to measure wave heights to 10 cm verti¬

sion to opt for radar sensing was largely determined by the

cal accuracy and a scatterometer for measuring wind speed

meteorological conditions, and in particular the predomi¬

and direction at ocean surface (fig. 9.35).The instrument pay-

nance of cloud cover, prevailing in many ESA member states.

load also featured two passive sensors, a scanning radiometer

Germany played a particularly important role in the deci¬

operating in the visible and the thermal infrared and a Scan¬

sion-making process, especially in view of its industrial

ning Multichannel Microwave Radiometer (SMMR) similar to

strength in this area.

the one on Nimbus 7.

ERS 1 occupied a sun-synchronous orbit at an altitude of 785 km. It operated a 35-day orbital cycle until 20 December

Almaz

1993 but then switched to a 3-day cycle, a higher revisit fre¬

With the Almaz (‘diamond’) satellite series, the Soviet Earth

quency being more suitable for the study of ice cover during

observation programme entered new territory. Derived from

the Arctic winter. The repeat cycle was then extended to 168

military stations of the same name — which were subsequendy

days for the geodesic utilisation phase, which continued to

reinstated in the Salyut programme - the Almaz platform was

the end of the satellite’s service life on 10 March 2000. These

built by OKBTchelomei, now NPO Machinostroienya.

cycle changes were effected by means of very slight varia¬

The first satellite was ready for service in 1981 but its

266

tions in altitude and inclination.

launch was vetoed by the then Defence Minister D. Ustinov

The observation payload included a broad range of

who was on particularly bad terms with the engineer-in-

advanced technology sensors. The Active Microwave Instru¬

chief YN. Tchelomei. The programme did not resume until

ment (AMI) included a Synthetic Aperture Radar (SAR)

1984, the year in which both men died. A prototype with the

operating in the C-band (5.3 GHz) withVV polarisation.The

designation Kosmos 1870 was launched on 22 July 1987

SAR could operate in image mode, where it covered strips of

and underwent a two-year programme of testing. Almaz 1,

the Earth’s surface about 100 km across, whose central axis

the first operational unit, was launched from Baikonur on

was located some 300 km to the side of the satellite track

30 March 1991. It had a theoretical design life of two to

(see fig. 9.9a). In the second (‘wave’) operating mode, the

three years but in fact fell back in October 1992. This very

5 km x 5 km field provided discrete sub-images every 200 or

large spacecraft weighing over 18 tonnes and measuring

300 km. The two modes were mutually exclusive. The AMI

15 metres end to end operated from a 300 km orbital alti¬

also featured a scatterometer used to determine wind direc¬

tude at 73° orbital inclination. Orbits could be adjusted to

tion and speed at the surface of the sea by means of measure¬

enable the satellite to acquire close-up images, a common

ments taken across a 500 km wide swath, with a standoff

SAR-EQUIPPED EARTH RESOURCE SYSTEMS

Figure 9.35. Cartographic representation of winds at the surface of the sea

scatterometer readings. The earliest studies of this kind were carried out in

based on Seasat scatterometer readings. An understanding of wind phenom

1978 using Seasat-this image of wind speed and direction at the surface of

ena at global level is essential to the study of energy exchanges. Work in

the Pacific Ocean was acquired using the Seasat scatterometer. The colours

this area had fora longtime to rely on the study of cloud displacement but is

represent wind speed and the arrows wind direction. Image NASA, produced

now backed up by the mapping of sea-surface winds based on spaceborne

byJPL.

between 250 km and 750 km to the right of the satellite

item in the ERS 1 payload is the Along Track Scanning

track. Measurements were taken in relation to three axes pro¬

Radiometer (ATSR), a high-precision passive microwave

ceeding from the sub-satellite point. One axis was perpen¬

instrument operating in the infrared. Two final instruments

dicular to the satellite track, the other two following the

equipping ERS 1 are the Precise Range and Range Rate Equip¬

bisectors forward and backward of the angles formed by the

ment (PRARE), which failed to function correctly from the

ground track and the first axis (see fig. 9.11). Backscatter

time the satellite was launched, and a laser reflector. Data col¬

readings for a given point on the surface of the sea were thus

lected by the SAR far exceed on-board recording capabilities

taken in succession (forward beam, perpendicular beam and

and it has therefore to transmit over 100 million bits of infor¬

lastly backward beam) with very short time intervals.

mation per second in real time to ground receiving stations.

ERS 1 also carries a radar altimeter working in the Ku-band

The ERS satellites are essentially multidisciplinary in scope.

(13.9 GHz) for measurements of vertical distance to 10 cm

Information provided by the infrared radiometer concern¬

accuracy. The altimeter can be used to determine the frontier

ing ocean surface temperatures and by the radar altimeter

between free-flowing sea and pack ice, the elevation of the

(operating in ‘ice’ mode) concerning the evolution of polar

polar icecaps or the significant height of ocean swell. Another

ice cover is of great relevance to environmental research and

!

267

268

Earth observation

150°

150°

120°

120°

Klruna Arctic circle 0 Fairbanks

60° 0 Prince ; Albert Gatineau

0 NqinriSn Maspalomas

Hyderabad

Cotopaxi

Ingapoi

Cuiaba Cordoba

Alice Sprii Johannesburg

Hobart

Syowa Antarctic

O'Higgins

Figure 9.36. ERS 1 data receiving stations January 2000.

the study of changes at global level. The prominence given to

Wavering by Japan on pricing for JERS data does however

study of the ice regions is clear from the geographical loca¬

reveal some inconsistencies in its national space policy. MITI,

tions of the receiving stations at Kiruna, Tromso, Fairbanks,

which was responsible for the instrument payload, preferred

O’Higgins, Syowo and McMurdo (fig. 9.36). In ‘ocean’

to pitch prices low, whereas NASDA, in charge of the plat¬

mode, the radar altimeter provides considerable information

form, took a more commercial stance along the lines of SPOT.

on marine topography, from which the strength of ocean

The obligation on Japan, arising out of its special relations

currents — variations in which are responsible for certain cli¬

with the United States, to refrain from protectionist policies

matic changes - can be derived.

(that is, policies designed to give domestic industry an edge

The SAR images supplied by the AMI are probably the most

over international competitors) in the commercial arena

important ERS contribution to environmental knowledge,

undoubtedly contributed to the adoption of low prices.

despite the fact that the AMI can only operate for ten minutes

Another factor was a concern to be seen as a ‘good world

in every orbit and even then only when it is in sight of a

citizen’ and even to acquire, through generous policies, a

receiving station. These images provide immensely useful

measure of regional influence. Finally, the emphasis on mar¬

material for a whole range of disciplines in biology, geology,

itime rather than land observation reinforced the scientific

hydrology and geography (fig. 9.37). The follow-on ERS 2 satellite, launched on 21 April 1995, carries an AMI and radar altimeter similar to those on board ERS-1, an enhanced

Figure 9.37. Images acquired by the Seasat and ERS 1 SARs. a) Seasat: Image of the cove at Aiguillon (in Western France) at high tide

ATSR, an improved PRARE and a new instrument, the Global

acquired by the Seasat SAR (L-band) on 27 August 1978. The areas of

Ozone Monitoring Experiment (GOME). The two craft oper¬

weaker backscatter, shown in black, are characteristic of the uniform mud

ated in tandem from 16 August 19 9 5 to mid-May 1996. Since

flats at the fringes of the cove. Backscatter is strongest over water. The

2002, the data (fig. 9.38) are aquired by Envisat 1 (see chap¬

transient shore line is particularly well delineated where very smooth mud flats are bordered by backscattering water. Image © NASA.

ter 7, p. 169). b)

JERS1 (Fuyo 1) The launch by Japan of the MOS satellite in 1987, the JERS radar satellite in 1992 and finally ADEOS 1 in 1996 demon¬

ERS 1: Image of the cove at Aiguillon at low tide, acquired by the ERS 1 SAR (C-band) on 8 November 1991. Contrasts in orientation of surface roughness appear clearly on this image. The areas of weaker backscatter, shown in black, are characteristic of the uniform mud flats at the fringes of the cove and of the beaches at the Argay headland. Stronger backscatter

strates a strong and consistent interest in satellite observation. Development of an 18m resolution civil radar capability, in

is recorded where ripple marks run perpendicular to the radar beam (the central part of the cove to the north of the Sevre Niortaise area) or where

the shape of the L-band SAR carried by JERS 1, was a first in

the bank of a channel is at right angles to the beam direction. Areas of

this frequency band. The OPS sensor supplies optical data

strong backscatter are shown in white on the image. A: Aiguillon cove;

with the same resolution (18 m) and offers stereoscopic

P: Argay headland; S: Sevre Niortaise.

capability but these features are much the same as for Landsat.

Image ERS 1, © ESA (R), processed by Geosystemes.

SAR-EQUIPPED EARTH RESOURCE SYSTEMS

!

269

270

|

Earth observation

Figure 9.38. Multispectral image acquired by the Envisat 1ASAR sensor. This image depicts Weddel Sea and Antarctic Peninsula. © ESA, 2002.

15.3° forward for stereoscopic imaging. Resolution is 18 m in all spectral bands.The scenes obtained cover a 75 km x 75 km area with a resolution of 24.2 m along the track and

and experimental nature of the programme - which in any case never got beyond this first satellite.

18.3m across the track. When JERS came to the end of its operational life in

JERS 1 (Japanese Earth Resources Satellite), launched in

autumn 1998, a little over a year after the premature end of

February 1992, operated from a sun-synchronous orbit at an

the ADEOS 1 mission, Japan’s Earth observation capability

altitude of 568 km.This relatively low altitude implied a need

came temporarily to a halt. And since no high resolution sen¬

for weekly orbit adjustments in order to keep to a regular

sor will figure among the instruments carried by ADEOS 2,

44-day cycle. JERS 1 operations terminated in autumn 1998.

due to be launched in 2002, the ALOS satellite (10 m SAR,

JERS carried an Optical Sensor (OPS) collecting data in

2.5 m PAN) billed for launch in 2004 becomes an even

the visible and near infrared and a synthetic aperture radar

greater priority, at a time when Japan is giving increasingly

(fig. 9.39).The OPS operates in seven spectral bands: B1 (0.52

serious thought to the prospect of acquiring a high resolu¬

|xm-0.60 pm), B2 (0.63 pm-0.69 pm), B3 and 4 (0.76

tion capability for civilian and military reconnaissance.

pm-0.86 pan), B5 (1.60 pan-1.71 pun), B6 (2.01 p,m2.12

|xm), B7

(2.13

pun-2.25

pun), B8

(2.27

In this connection, the new political context created by

p,m-

the August 1998 firing of a North-KoreanTaepo Dong mis¬

2.40 pun). The B3 sensor is nadir-viewing whereas B4 views

sile, making regional monitoring a strategic priority for

SAR-EQUIPPED EARTH RESOURCE SYSTEMS

Figure 9.39. JERS 1SAR image. Acquired on 16 October 1992, the image

Japan, could well shift the programme into higher gear. It is

shows part of the same region as that appearing in fig. 9.32. © NASDA1992.

likely however that the programme of surveillance satellites approved in 1999 will evolve more or less in parallel with

650 km.The first operational unit, Okean O 1, was launched

the civil programmes, insofar as it is prompted by defence

in 1988. Designed for ice zone studies and oceanography,

objectives which have little in common with the civil space

these satellites carry a side-looking radar operating in the X-

considerations which

space

band and a number of scanning radiometers. Their orbit

capability. The special relationship between Japan and the

allows them to revisit the same location twice a day. Once

United States in security matters — a relationship embodied

Okean data received by Meteor primary stations has been

in a specific defence agreement — may result in suitably

processed, it can be relayed via Ekran geostationary satellites

adapted American systems being chosen in preference to

to the ships concerned.

have

shaped

the

existing

national products.

The first of this family of satellites to be built after the break-up of the USSR and Ukrainian accession to indepen¬

Okean and Sich

dence was Sich 1, launched in 1995. This craft was jointly

The Okean O satellites manufactured by the Ukrainian firm

owned by Russia and the Ukraine but subsequent output

NPOYuzhnoye operate from a circular orbit at an altitude of

is likely to be produced separately for the two countries.

j

2J\

272

I

Earth observation

the programme came with the conclusion of an agreement between the Canadian Space Agency and the firm MacDonald Dettwiler for construction of Radarsat-2. Radarsat-1, launched in November 1995, operates in Sunsynchronous dawn-dusk orbit at an altitude of about 800 km (see fig. 2.29). It carries only one sensor, a synthetic aperture radar. This very advanced instrument operates at C-band wavelength with HH polarisation and provides scope for using a variety of incidence angles, from 20° to 50°, and, for experimental purposes, from 10° to 20° and from 50° to 60°. Swath widths vary too, as does viewing direction. Primarily designed to support study of the arctic regions, Radarsat-1 normally performs oblique viewing to the right — i.e. to the north - of its orbit path. But viewing direction was success¬ fully changed to the left on two occasions to accommodate observation of the Antarctic — and indeed almost total cover¬ age of this region was obtained (fig. 9.11). To do this, the satellite was twice rotated 180° around its vertical axis. User enthusiasm for Radarsat data and the increased Cana¬ dian share in the imaging market has led to the development of the Radarsat-2 programme, although along different lines. In fact, this development officially makes the transition from mainly public to private financing. It has also led to reflection on Radarsat-3 which may correspond to a new approach based on cooperation whilst still moving towards predomi¬ nantly private investment. Figure 9.40. First SAR Image asquired by Radarsat 1. Courtesy of Canadian Space Agency.

Launch of Radarsat-2, with a claimed 3 m resolution, is scheduled for 2003. This project, which benefits from an innovative funding arrangement whereby a private firm cov¬

Russia’s Okean O satellite, launched on 17 July 1999, is fitted

ers development costs while the Canadian government agrees

with additional sensors for Earth Observation and atmos¬

to buy a volume of data fixed in advance, is driven by a com¬

pheric studies.

bination of competitive and cooperative goals. An initial

Launch of the Ukrainian Sich 2 satellite is currently at the

commitment by the United States to launch the satellite was

planning stage. It is expected to carry an SAR, unlike the Sich 3

however reassessed in view of the competitive threat Radarsat

follow-on unit funding for which is in any case still unsure.

may pose to the new LightSAR satellite to be developed by NASA and a private company and of concern being expressed

Radarsat

by the Department of Defense about the security implications

The Radarsat programme has a long history and the initial

of the resolution which the new Canadian craft will appar¬

choices were heavily influenced by Canada's physical location

ently offer. After some attempts to investigate a link-up with

and characteristics. Canada's commitment to radar remote

ESA with which it has a cooperation agreement, and having

sensing is prompted by a number of geographical constraints:

emphasised complementarity with Envisat, the European

a vast and often inaccessible territory, concern to exploit nat¬

remote-sensing platform, Radarsat-2 will be launched com¬

ural resources, heavy cloud cover, priority assigned to ice

mercially by the United States. Canada and the US have con¬

studies. Radar offered the most effective means of meeting

cluded a specific agreement concerning the distribution of

these needs and at the same time an opportunity to develop a

data in order to secure their national interests.

special capability in a high-tech niche - a favourite with space

The Canadian Space Agency’s decision in February 2001

sector managers around the world, concerned to find more or

to carry out a mission feasibility study with MDA for the

less exclusive openings for national products (fig. 9.40).

development of Radarsat-3 corresponds to yet another logic.

The objectives set for Radarsat - the first mention of

Radarsat-3 would be launched soon after Radarsat-2 in order

which is in fact to be found in the context of Paxsat, a major

to benefit from combined use of the two satellites. The aim

treaty verification project dating back to the 1960s - were

here is to enhance Canadian commercialisation capacities in

very ambitious and this no doubt is why the project fell so

partnership with the value-added sector, whilst at the same

far behind schedule and went so far over budget. But it is.

time contributing to a global understanding of the environ¬

nevertheless the only civil operational spaceborne radar sys¬

ment. Synergy with the European programme GMES, still

tem in existence. Confirmation of the dominant position of

under definition (see chapter 7), has also been envisaged.

Remote sensing - the way ahead

Over the last ten years the number of remote-sensing systems

side aperture radar operating in the X- and L-bands together

has grown rapidly and the range of facilities offered has

with a number of other very advanced sensors, such as the

become more diverse. This has been reflected in an expanding

Ikar II radiometers. But while manned space missions

user community. At the present time two development trends

provide scope for innovative experiments and creative obser¬

can be distinguished. A first trend is to exploit the greater

vation and while Mir has produced a rich harvest of photo¬

resolving power now offered by sensors to survey landforms

graphic images, they are ill-suited to systematic, continuous

on a large scale. Civil activity in this area is likely to surge for¬

collection of images of the Earth.

ward with the advent of the very high resolution systems

The major shift in emphasis seems to have come in the

whose products have only recently come onto the market and

1990s, with the development of radar sensing and launch of

which are now becoming serious rivals for aerial photography.

the Almaz, Radarsat, ERS, and JERS satellites — despite the

A second development line is to exploit the global scope of this

decision not to go ahead with an SAR for EOS. Radar sensing

technology and its integrative potential — allowing vast surface

is valued not only for its ability to ‘see through’ cloud cover

areas to be characterised by single values. Progress here is sup¬

but also for the enormous wealth of images which can be

ported by lengthening time series, a wider range of spectral

obtained at varying incidence angles and with different

bands and more sophisticated sensors capable of collecting

polarisations. The American LightSAR project is built around

data on different phenomena simultaneously. This opens up

an L-band radar offering multipolarisation and a range of

previously undreamed-of possibilities for global modelling.

resolutions, some down to 1 m to 3 m. Using interferometry techniques, it will be capable of detecting very slight changes

Widening range of sensors

on the Earth’s surface.

The earliest remote-sensing missions relied on optical sen¬

Remote sensing is being pushed forward by new pro¬

sors. Their subsequent history has been marked by continuity

grammes too. Under the European Polar Orbit Earth Observa¬

combined with gradual diversification.The United States and

tion Mission (POEM), two satellites will be placed in orbit -

France are moving ahead with their Landsat and SPOT pro¬

METOP (see p. 243) and Envisat 1, launched in 2002. For

grammes, with a commitment to continuity of service, as

budgetary reasons, the Envisat mission will use the polar

expected by customers who have invested in dedicated pro¬

platform solely for Earth observation purposes. Envisat will

cessing systems and have in some cases even established their

in some ways take over from ERS 1, carrying an Advanced

own data receiving stations. At the same time the range of

Synthetic Aperture Radar (ASAR) and an advanced Along-

suppliers for this type of product has begun to widen: India

Track Scanning Radiometer (ATSR) not unlike those which

has opted for development of its own satellites and Japan

equipped the earlier craft.

has acquired an optical - in addition to its radar-imaging —

There are also plans to use hyperspectral sensors, designed

capability. Cooperation has been another line of approach, one

to break incoming signals down into a large number of spec¬

example being joint development by Brazil and China of the

tral bands. The instrument payload on board the Lewis satel¬

CBERS satellite. Finally, with small satellites such as Uosat now

lite included such a sensor - previously only tested from

coming onto the market, the number of countries able to

aircraft - but the mission failure prevented the experiment

acquire their own satellite sensing capability is set to rise.

going ahead. Hyperspectral sensing features in a number of

The need to supply images in standard format is not however

current satellite projects in the USA: NASA is planning to test

inconsistent

designs — which is

the Hyperion sensor under the New Millennium programme

why Landsat 6 (which failed to reach orbit), Landsat 7 and

and the Navy and Air Force are showing a keen interest in the

with

evolving

sensor

SPOT 4 and 5 differ from their predecessors while providing

Navy Earth Map Observer (NEMO) and Warfighter 1 pro¬

data continuity.

jects. Australia too is working on a small satellite which will

Meanwhile a number of civil remote-sensing missions were taking advantage of flight opportunities in the Ameri¬

carry a sensor of this kind, the Australian Resource Informa¬ tion and Environment Satellite (ARIES).

can and Russian manned spaceflight programmes, on board

This movement is increasingly accompanied by the devel¬

the Shuttle with the successful SIR flights and, until 1999, on

opment of other non-imaging Earth observation techniques.

the Mir space station with its various specialised modules.

Radar altimetry, for example, is providing the basis for ever

The Spektr module for example was equipped with a whole

more sophisticated models - but they are useful primarily as

series of instruments for measuring the lower atmosphere

a contribution to understanding phenomena at the scale of

and the Earth’s surface, while the Priroda module featured a

the planet. With the available images already covering the 273

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Canada USA Latin America Europe Arabsat countries Israel Turkey

Figure 10.10. Chronology and initial positions of civil geostationary

first stationed, although they may since have moved from those positions,

telecommunications satellites. Positions on orbits are where satellites were

Satellites represented by pale colours, with names written in italics, were no

VF2

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1990

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1992

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1993

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1990

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76-80 70-75 64-69

291

292

Telecommunications

satellite can thus be envisaged, not just as a simple relay, but as

opportunities, the main unknown is undoubtedly the multi-

a supplier of information, concerning the weather, position¬

media market. At the present time, interactive applications

ing, risk management, and so on. Despite this, the global cov¬

take place rather on a local scale. Although technically well

erage provided by most satellites involved in this type of

suited to data distribution, satellite systems must resolve a

activity is not continuous and this means that a certain num¬

number of difficulties in order to achieve real interactivity. Space telecommunications have favoured geostationary

ber of technical difficulties remain to be overcome. Mobile telecommunications certainly offer new opportuni¬

systems for over forty years now, their technical characteris¬

ties, with an annual growth of 25%.The market share held by

tics being well suited to the missions involved. With the

satellites in this area, which has already seen drastic deregula¬

identification of new services, the idea of low- and medium-

tion, should be of the same order of magnitude as held across

Earth orbiting satellite constellations has become more

the whole telecommunications market, that is, a few percent.

attractive. In this context, mobile phone projects greatly

In such conditions, only a small number of systems would

increased in number at the end of the 1990s. But this has not

appear to be viable, all the more so in that the investment

spelt the end for geostationary satellites. Difficulties encoun¬

required is enormous. Certain geostationary systems are

tered in financing constellation programmes, as witnessed

already capable of providing such services and the constella¬

by the bankruptcy of the Iridium society and also the prob¬

tions which should be able to provide universal coverage find

lems finding financial backing for ICO in 2000, show that it

themselves confronted with a lack of real markets in precisely

is still hard to assess the importance of this turning point.

those regions with the poorest terrestrial means of communi¬ cations, for which satellite is supposed to represent a genuine

Predominance of geostationary satellites

interest. In addition to this, the deregulatory nature of satellite,

Deploying geostationary satellites is a delicate operation (see

which is in theory free of any constraint laid down by local

chapter 2), but their apparent relative immobility greatly

operators, does not help in attracting the latter. The constraint

simplifies the ground segment. The size of antennas can be

imposed by gateways and the desire to interact with the terres¬

limited as satellite power increases, so that terminals can be

trial network in programmes like Globalstar (see fig. 10.20)

developed at lower cost. Another advantage is that lifetimes

tend to compensate for these handicaps, although rather to the

can be as long as 15 years, which helps to smooth the prob¬

detriment of satellite’s specific advantages.

lem of costs. The launch programme for geostationary satel¬

Apart from encouraging prospects associated with the

lites shows the rising number of such systems as time goes

development of Internet, where satellites will certainly find

by and also the wider range of user nationalities, although

I960

1965

1970

Relay 2

OSCAR 1'

'02

03"

““04

0 5 (Aus)

*

0 9 (UosatlUK)^^:

OSCAR Series (Orbiting Satellites Carrying Amateur Radio)

0 11 (Uosat-2 UK) 0 12 (Fuji 1 Jap) 0 14 |Uosat 3t Healthsat 1 UK) * 0 15 (Uosat 4 UK) ' ' 016 (Microsat 1): ■ 0 17 (Microsat 2 Bra 018 (Microsat 3)1 0 19 (Microsat 4 Arg)1 0 20 (Fuji 2 Jap) 1 0 21 (RS14, Informator) 1

American Soviet, then Russian Other

0 22 (Uosat 5 UK) ■ Tubsat A (Ger) ■ 0 23 (Kitsat 1, Uribyol 1 Korea) ■ S80 T (Fr) ■ 0 24 (Arsene Fr) ■ Temisat (It) ■ 0 25 (Kitsat 2, Uribyol 2 Korea)1 0 26 (Itamsat It) *

Radio-Sport Series (or Radio Sputnik, amateur radios)

0 27 (Eyesat 1) * 0 28 (Posat 1 Port) 1 Healthsat 2 (UK) ' RS 15 (Radio ROSTO) 1 0 29 (Fuji 3 Jap) ■ S 41 — S Jr 3 ■ Stensat ■■■ Saudisat 1-2 S Amsat P3D

Figure 10.11. Chronology of civil non-geostationary telecommunications satellites. Constellations beginning after 1991 are shown in fig. 10.12.

.

Missions

I

the number of space powers capable of carrying out this type

niya programme, begun in 1965, was an answer to the spe¬

of launch remains extremely limited (fig. 10.10).

cific geographical situation of the Soviet Union, and in partic¬

Between 1964 and 1975, the United States was the only

ular to the need to provide services in high latitude zones. The

nation with the technical knowhow to launch and deploy

name of the satelhte means ‘lightening’, corresponding to its

geostationary satellites. From 1966, they have carried out an

apparent path over Russian territory (see fig. 3.22). Indeed,

increasing number of launches for their own programmes or

Molniya orbits have perigee at 500 km and apogee at

those of their partners, the international company Intelsat,

40 000 km. With a period of 12 hours and reduced displace¬

the United Kingdom and Canada. Since this period, the con¬

ment speed at apogee, relative to the Earth’s rotation, they

struction and launch of geostationary satellites has repre¬

remain roughly 8 hours over the Soviet Union. The interest of

sented the main market for space activities.The large number

such systems is twofold. Firstly, they can provide services at

of launches between 1966 and 1969, signalling the strong

very high latitudes (see fig. 10.2) whereas geostationary satel¬

demand at this time, eventually stabilised at around five

lite coverage cannot go above 81°. Secondly, it is much easier

launches per year (see fig. 4.4).

to place a satelhte into Molniya orbit than into geostationary

The USSR generally used the more economical Molniya

orbit when the launch pad itself is located at a relatively high

orbits, given its shortage of low latitudes. It was not until

latitude (see fig. 2.35). However, the lifetime of electronic

1974 that it positioned its first geostationary satellite, and

equipment is reduced by repeated crossings of the Van Allen

from then until 1978, only launched one or two others per

belt (see fig. 1.2) and more stations must be provided, even if

year. The annual number of such launches then reached the

the antennas equipping them are smaller in size. For these rea¬

same level as the United States, whereupon Russia set about

sons, since 1975, several families of geostationary satellites

pursuing much the same policy.

have been installed to complement the Molniya system.

The 1980s are marked by the arrival of new players. This was when Japan launched its first geostationary satellite,

New constellations and new services

using a rocket manufactured largely under American licence.

During the past few years, technical progress has been made

Europe for its part became capable of carrying out its own

in antenna technology, and also in on-board signal process¬

launches in 1981, using the Ariane launch vehicle. It was

ing capacity and electronics. Combined with the new needs

then able to free itself from the American monopoly as far as

of mobile communications, private users and multimedia,

commercial space communications were concerned. The last

this has led to what some would qualify as a genuine revolu¬

to arrive on the scene was China, placing its first experimen¬

tion: projects involving constellations of non-geostationary

tal geostationary satellite in orbit in 1984.

satellites in Low-Earth Orbit (LEO), Medium-Earth Orbit

Since then, with the exception of India, which developed its

(MEO), and even in High Eccentric Orbit (HEO).

own launch vehicle in order to access the GEO orbit, the trend

These constellations of satellites with apparent motion

in the 1990s has been towards an increased number of coun¬

across the sky (sometimes referred to as orbiting satellites, as

tries and more and more private consortiums merely possess¬

opposed to ‘fixed’ geostationary satellites, fig. 10.12) illus¬

ing geostationary satellites, rather than launching satellites

trate a new commercial philosophy favouring flexible use

themselves. Asia is a case in point; although the trend slowed

and small ground-based terminals. Costs must be reduced by

down somewhat with the financial crisis of 19 9 7—19 9 8, it was

mass producing equipment with less demanding technical

soon reaffirmed during 1999—2000. The development of geo¬

specifications. A complex set of factors has made this

stationary systems was a decisive factor in the establishment of

approach possible, including progress in miniaturisation

the space market, both in terms of satellite manufacture and

resulting from military research programmes such as the

launches; and they maintain a key role in setting up national

Strategic Defense Initiative. It marks a reverse trend that is

programmes and distributing traditional services such as tele¬

likely to continue, although probably in a more modest way

vision, or more novel services such as access to Internet.

than was originally expected in the mid- 1990s.

For more than 35 years, GEO satellites have heavily out¬

Examining the projects and programmes as of the summer

numbered other satellite systems, at least for civilian applica¬

2000 (fig. 10.13), it is clear that the number of planned con¬

tions, since some Russian and American military systems

stellations is well down compared with the many projects

continue to be developed for purposes far removed from any

that saw the light of day in the second half of the 1990s. The

commercial motivation (see chapter 12).The programme of

Iridium programme studied by Motorola as early as 1987 had

low-Earth orbiting telecommunications satellites (fig. 10.11)

a decisive influence, stimulating competitive projects with

shows that the use of low orbits corresponds to two highly

Globalstar in 1989 and Project 21 (which became ICO) in

specific cases. The first are small satellites for amateur radio

1991. It then caused a minor crisis in the financial world

enthusiasts seeking easy low-cost access, and the second are

when bankruptcy struck after just six months in action (see

the Molniya satellites.

p. 306). Several factors can help to explain this development.

The existence of low-Earth orbiting satellite programmes

The main theoretical interest of these constellations is to

providing similar services to those of geostationary satellites is

guarantee users flexible links without requiring Earth-based

an innovation attributable to Soviet space activities. The Mol¬

installations at all points of the globe. On the other hand, the

293

Telecommunications

sations, can only lead to hostility from certain operators. Comparing the Iridium and Globalstar programmes (see pp. 306-307), it would seem that current trends favour space systems that complement terrestrial networks rather than maintaining their independence from them. The ICO project was originally designed by Inmarsat, an organisation specialised in mobile communications, which has been privatised. Amongst the founding projects, this has been the one the most adversely affected by the Iridium fail¬ ure. After its bankruptcy in November 1999, ICO became NewICO in May 2000, merging with ICOTeledesic Global. Although less well known, the Ellipso project also remains plausible insofar as it proposes an original architecture involving satellites in eccentric orbit, thereby ensuring better services in the target regions, where it aims to develop fixed stations with larger but cheaper terminals. At the same time, financial obligations compelled them to enter a coordination with ICOTeledesic Global. Teledesic or Skybridge correspond to a different type of pro¬ ject. Designed later, they are also intended to provide multime¬ dia services. The thinking behind the two systems once again bears witness to a difference of approach, the space system being autonomous or complementing terrestrial networks. Teledesic is a joint project from Motorola, Boeing and Matra Marconi Space. It was originally the most ambitious, since it was to comprise 800 satellites with on-board switch¬ ing and inter-satellite links ensuring continuous and global coverage. The gradual fall in the number of satellites to fewer than 3 0 0 in 1998, then fewer than 10 0 in 2 0 0 2, is witness to the difficulty of financing this type of project, as well as its still rather experimental nature. Developed by Alcatel and Loral, the Skybridge system set Figure 10.12. Chronology of constellations of non-geostationary telecom¬

out to complement rather than compete with terrestrial net¬

munications satellites launched between 1991 and 1 January 2001.

works for Internet access. Far less complex, and hence cheaper, it relies on satellite flexibility to fill the gaps in-the

profits from such an approach remain limited insofar as the

terrestrial network, for example, providing immediate initial

number of potential users remains small, whilst the system

services to new users. The use of both GEO and LEO satellites

itself must be technically complex. Comparing the two pro¬

further strengthens the credibility of the project.

grammes so far completed, Iridium and Globalstar, it is clear

One last feature is striking, namely the preponderance of

that the existence of a market is more important than the spe¬

American companies amongst the operators proposing these

cific advantages of a space operation. Iridium, designed as an

systems, whether they aim to provide domestic or interna¬

autonomous space service, was equipped with miniaturised

tional services.

switching on board its satellites so that it could operate quite

Although Global Mobile Personal Communications Satel¬

independently of terrestrial networks. In practice, however,

lite (GMPCS) services and transmission of multimedia data

terminals proved difficult to set up correctly and relatively

are the main motivation for new constellations, the identifica¬

expensive. This limited the number of subscribers, particu¬

tion of new services does not only concern non-geostationary

larly as terrestrial cellular telephones have seen a faster and

satellites, whatever the degree to which programmes may

more substantial development than was predicted at the

have been implemented. From the standpoint of space occu¬

beginning of the 1990s. The latter have been able to reduce

pation, it seems that many projects are based upon geostation¬

charges in consequence, whilst space systems remain rela¬

ary satellites, particularly in Asia. Certain types of service,

tively costly for private users. In addition, the liberalisation of

although sometimes also offered by alternative systems such

the telecommunications market related to deregulation has

as mobile phones, would nevertheless appear to favour certain

led to roaming agreements between terrestrial mobile phone

types of orbit.

operators, whereas the self-sufficiency of space systems with

Hence broadcasting services (radio, television, video)

regard to the terrestrial network, which may be valued by a

remain very much the domain of projected geostationary

limited number of users, in particular, governmental organi¬

satellites whilst messaging applications seem well suited to

Missions

VHF Band 200 MHz




Asiasat 3 S C band Asiasat 3 S Ku band East Asia beam Asiasat 3 S Ku band South Asia beam Asiasat 3 S Ku band steerable beam State at least partially covered

Figure 10.25. The Asiasat system in January 2000,

Regional systems

Figure 10.26. The ACeS and Singapore-Taiwan systems in January 2000.

ties, space-based projects began to increase in number, gener¬

Hutchinson Whampoa of Hong Kong and Cable and Wireless.

ally taking on regional dimensions, in response to the trend

In 1999, the latter two investors brought in the European

towards privatisation and globalisation (fig. 10.24).

company SES, keeping a 49.5% stake.This operation marked a new need for space operators to obtain global coverage. Asiasat

■ SES-ASTRA

1, the former Westar satellite, was taken over and relaunched

As the United States never developed any regional-like satellite

in 1990, whilst Asiasat 2 was launched in 1995 and Asiasat 3

system per se, Europe offered the first example of a genuine

on 21 March 1999 to replace Asiasat 1. According to its opera¬

regional system based on the Astra system managed by the

tors, it covers two-thirds of the world population and its latest

Societe Europeenne de Satellites (SES). With Luxemburg as its

satellite covers more than 50 countries in Asia (including

main shareholder, it is renting transponders that are made

China and India), the Middle East, and CIS countries, as well as

available to radio broadcasting companies than can use them

Australia (fig. 10.25).The services provided are highly diversi¬

on their own or in association in a network. The business-

fied, ranging from public telephones to private VSAT services,

orientated activity as well as the limitations inherent to a

and including high speed Internet and multimedia links.

strongly competitive European market partly occupied by Eutelsat, have led SES to buy shares in international consor¬

■ Measat

tiums involved in new markets. In 2002, SES-Astra, equipped

In

with 12 satelhtes positioned on 3 orbital slots, is providing

Systems sent two satelhtes into orbit to form a new regional

now a significant number of very powerful transponders to

network MEASAT, providing broadcasting and telecommuni¬

broadcasters or to multimedia companies. More over, new

cations services in the Far East, India, the Philippines and

partnerships with operators in Scandinavian countries, Latin

Australia (fig. 10.24).Two further satellites extend coverage to

America and Asia, as well as the acquisition of the US operator

China, the Middle East and Africa.

1996, the Malaysian private firm Binariang Satellite

Americom, led to the creation of SES-Global.The company is now active in 4 continents and is presenting itself as a strategic

ACeS

investment for a significant number of satellite operators.

Asia Cellular Satellite (ACeS) is the first regional satellite system dedicated to mobile personal telecommunications,

■ Asiasat

with coverage exclusively aimed at the Asia—Pacific region

In Asia, the first effects of deregulation were felt in Hong Kong

(fig. 10.26). It is the joint property of several Asian partners.

in 1990 with the creation of the consortium Asia Satellite

Launched on 12 February 2000, Garuda 1 provides state-

Telecommunications Company, or Asiasat. Set up to exploit

of-the-art mobile telephone services as well as data usable

commercial space telecommunications, the company was

on private terminals at very low costs. Agreements have

formed by the China International Trust and Investment Cor¬

been reached with more than 43 terrestrial cellular network

poration (CITIC), together with two other shareholders,

operators in 26 countries, including China, and a second

313

314 I Telecommunications

satellite is planned to serve both as a backup and also to

in May 2000, to provide GSM mobile communications ser¬

extend ACeS coverage to Central Asia, Eastern Europe and

vices to almost 40% of the world population. The company is

part of North Africa. The system has aimed at a regional

mainly composed of shareholders from the Arabic countries,

approach capable of competing with Iridium and Global-

including those involved in Arabsat, but also the American

star’s international policy.

giant Hughes Space and Communications, who manufactured



the satellite.The service is in principle guaranteed for 15 years, ■ Thuraya

given the lifetime of GEO satellites. Such a low cost system

The regional system Thuraya, named after a star cluster in the

should provide services to more than 100 countries, across a

constellation of Taurus, was launched by the private firm Thu¬

zone covering the Indian subcontinent, Central Asia, the Mid¬

raya Satellite Communications Company, with a first satellite

dle East, North and Central Africa, and Europe.

National systems

The very idea of a national system has also changed consid¬

into international consortiums such as Global Alliance and

erably through the new role played by private entities in

the extension of coverage beyond national territories repre¬

competition with state-run organisations. The American case

sent significant changes.

undoubtedly serves as an extreme example, spelling the end

National systems have developed in response to a range

of a specific definition for this type of service, but even if the

of different concerns (fig. 10.27). They were originally

dividing lines are less clear, combination of national systems

established by developed countries needing to cover a vast

§ m

180°

150°

120°

Figure 10.27. National space telecommunications systems in January 2000. Satellites are shown in the colour of the country they belong to.

National systems

{

and unequally occupied territory with telephone and tele¬

develop their television broadcasting capabilities beyond

vision broadcasting services (see fig. 10.14).The first such

their own borders, when necessary. The latest systems

countries were Canada, the United States and the Soviet

brought into service in Thailand, Turkey, South Korea, Israel,

Union. From the 1970s, they had complemented their ter¬

Malaysia, Argentina, and Egypt correspond to the develop¬

restrial networks with space systems. Other national sys¬

ment of increasing national needs, but also to political and

tems were set up later, between 1983 and 1985, by the

commercial concerns. This is the case in Egypt where Nile-

more advanced amongst the developing countries, such as

sat, the first direct broadcasting Arabic satellite, is used to

India, Indonesia, China, Mexico and Brazil, and also West¬

relay national cinema productions.

ern countries like France, Australia and the United King¬

The announcement of the first African satellite launch for

dom, the latter concentrating on military satellites. The

2002 by the regional organisation Rascom shows that the

trend continued from 1989 to 1992 with Japan, Sweden,

African continent still lags behind. This is due to the low

the United Kingdom, Germany, Hong Kong, Spain and Italy

level of its own needs but also, above all, to a lack of invest¬

establishing their own space networks. All these cases repre¬

ment. Indeed, national satellites are not expected in the

sent countries keen to strengthen their trade capacity and

near future.

Turke;

Israel Taiwan

Thailand

Philippines

&

lalaysfa £]

Sing. □

!□□□ □ □□□□■ nana 1«l a, □□ a &a &□ tjA Indonesia

tfA

^ $

AUSTRALIA

180°

315

Positioning and navigation Overview Systems using downlink signals Systems using uplink signals

Overview

Navigation is the art of determining the direction to be taken

ment of atomic clocks, a key element of the system, clearly

by a craft on the basis of an exact knowledge of its position.

indicate a universal interest in this type of space activity.

Traditional use of the Sun, Moon and stars to take bearings is

For the established systems, the situation is quite different.

gradually being superseded by services available from artifi¬

Russia has gone in search of international collaboration that

cial satellites. These have greatly improved possibilities for

will bring financial backing for its system, whilst the United

identifying positions within an accurate universal reference

States, the only country to provide international services in

system that extends everywhere over land and sea, as well as

this domain, is seeking to maintain its technological lead and

in the air, regardless of weather conditions.

a suitable balance between civilian and military needs.

Only the United States and the Soviet Union have devel¬

Systems set up for radiopositioning and radionavigation by

oped worldwide satellite navigation systems, viz., GPS and

satellite comprise three segments. The first, on the ground,

GLONASS. Although initially set up for military purposes,

accurately determines the orbits of satellites (orbitography)

civilian applications soon became commonplace. Indeed,

and controls their positions, as well as providing users with

since the 1990s, these systems have grown into one of the

satellite ephemerides, among other things. The second is

main methods for positioning thanks to their accuracy and

made up of the satellites forming the reference network,

availability.

whilst the third refers to all users, whether they be on land, at

Although navigation was quickly identified by European industrialists as a key space application, the financial and technological difficulties involved in this type of system and

sea, in the air or even in space. Several systems fit into this general scenario. ■ Uplink systems: the ground-based transmitter may be

the absence of any decisive military need have meant that

simple, but the onboard receiver carried by each satellite

there has never been an independent European programme.

is complex and its transmission can be scrambled. Exam¬

The relative lack of interest can also be explained by the fact

ples are Argos, COSPAS-SARSAT, and DORIS.

that the US system is freely open to all, without charge, even

■ Downlink systems: satellites carry a simple payload, emit¬

though data available to civilian users was less accurate than

ting signals timed by an ultrastable clock. Examples are

that available to the US military up until May 2000. It is only

Transit, Kosmos-Tsikada, NAVSTAR-GPS (Global Posi¬

recently that Europe has really become aware of what is

tioning System) and GLONASS.

viewed as a strategic dependence, given the important appli¬

The position of the mobile is deduced from variations in the

cations for aviation and land-based activities, and considered

Doppler effect. The satellite supplies its exact position as a

developing its own complementary but interoperable system.

function of time and also the frequency of the signals, mak¬

Carried at last in March 2002 by the EU and ESA, Galileo

ing it possible to calculate the latitude and longitude of the

should be operational in 2008. In the same way, China’s

receiver. Extremely high precision less than 1 m in the best

launch of the beginnings of a constellation in 2001 and

cases can be achieved.

Japan’s continued research in key areas such as the develop¬

Systems using downlink signals

318

This is the main type of system used for navigation by satel¬

Global navigation satellite systems can be used in several

lite, since users can determine their position and velocity at

domains such as geodesy, aircraft navigation, and time syn¬

any moment. Such systems were first developed by the

chronisation. The number of users is on the increase. The

United States and the Soviet Union to satisfy military needs

most dependent applications are geographical surveying and

and subsequently opened up to the civilian sector (fig. 11.9).

mapping, together with the monitoring of agricultural land

Systems using downlink signals

and trawler fishing. Satellite-based navigation services are also

For GPS and GLONASS, the user has to measure a time dif¬

used in automobile navigation systems (an accuracy of 5 to

ference between the instant a satellite broadcasts its signal and

20 metres is needed). Combined with radio information

the instant the user receives the signal. This time interval mul¬

about traffic levels, these systems can optimise routes and

tiplied by the speed of light corresponds to a range, called the

make good estimates of journey times. Ever more precise,

pseudo-range, from the receiver to the space vehicle. With

such services are today capable of competing with ground

this information, the user’s position is located on a sphere

beacons for aircraft take-off and landing and even of moni¬

with radius the measured range, centred on the satellite. Navi¬

toring rockets during launch. However, the idea of using a

gation messages contain parameters called ephemerides spec¬

single system assumes a level of reliability that has not yet

ifying spacecraft orbits. Therefore, a user receiving three

been attained, in particular with regard to integrity parame¬

signals from three different satellites will be able to determine

ters, that is, the system’s ability to inform the user sufficiently

its position as the intersection of the three spheres (fig. 11.2).

rapidly when failure occurs. At the same time, navigation and

However, setting aside the theoretical aspect, there are two

telecommunications applications are tending to merge, thus

problems. First, the user and satellites have to be synchronised

giving access to new markets such as mobile phone services.

in time. The ground segment synchronises the constellation (e.g., the beginning of the initial GPS time reference was 6 Jan¬

Operating principles

uary 1980, which then changed to 22 August 1999). Natu¬

In the case of theTsikada and Transit navigation services, the

rally, the user cannot be exactly synchronised with GPS time,

first systems in this category to be developed, the satellite

since it costs too much to procure very accurate clocks. There¬

motion is known and the user position computed from mea¬

fore a fourth measured pseudo-range is needed to determine a

surements of successive Doppler or apparent frequency shifts

last state parameter, the user clock bias. The other problem is

of the signal as the satellite approaches or passes the user. This

that additional delays occur in the range measurements, such

yields the latitude and the longitude (fig. 11.1). The satellite

as atmospheric effects. Navigation messages contain correc¬

continuously emits two frequencies. These serve to transmit

tion parameters that can be used to estimate these delays

satellite positions and time references by phase modulation,

although not to determine the exact bias. The position com¬

but also to calculate distance differences by measurement of

puted using a navigation satellite system will not therefore be

Doppler frequency shifts. The receiver counts the number of

the true position. The better the additional delays can be esti¬

cycles received during a given time interval and the calcula¬

mated, the more accurate the computed position will be.

tion is carried out iteratively by comparing relatively mea¬ sured distance differences with those that would have been

Transit navigation satellite system

measured to the estimated point. Successive approximations

The Navy Navigation Satellite System, also called Transit, was

are made and the calculation stops when discrepancies grow

the world’s first operational satellite navigation service. This

smaller than some previously chosen value.

project was developed in the early 1960s to meet the precise navigation requirements of the US Navy’s ballistic missile

Satellite moves away from ground station

Satellite approaches ground station

submarine fleet. The first navigation sets were installed in

r*sT Signal received has longer wavelength and lower frequency than transmitted signal:

^Sr cf

'L* f

Signal received has shorter wavelength and higher frequency than transmitted signal: r\s\S\

Station Figure 11.1. The Doppler effect. The Doppler effect is used to determine the component of the satellite’s velocity along the line of sight. The frequency shift due to the satellite’s motion can be measured by counting the number of

S± ■

Murmansk Arctic circle £ Fairbanks

Edmonton

Petropaviovsk

Lannion Halifax Wallops

Toulouse 0 Yokohama

Hawaii

Cayenne

Darwin # Reunion

Cape Town

Wellington

Casey

Antarctic circle

329

330

!

Positioning and navigation

The Russian system COSPAS originally joined up with the

low altitude (850 km) facilitates use of the Doppler effect.

SARSAT programme (Search And Rescue Satellite Aided

The system can localise signals from a geographical region of

Tracking), jointly run by the United States, France and

radius 3000 km around each ground facility, or LEOLUT

Canada. The first Soviet COSPAS repeater was placed in orbit

(LEO Local User Terminal) (fig. 11.12).

aboard the civilian navigation satellite Kosmos 1383 in June

GEOSAR uses American geostationary GOES East and West

1982, whilst the first Western SARSAT was carried by the

satellites and geostationary Indian Insat satellites with

American satellite TIROS N in March 1983. Subsequently, a

transponders built into them. Insat covers the Indian Ocean,

series of American NOAA polar satellites and Russian

whilst the American GOES satellites cover the Atlantic and

Nadezhda polar satellites was launched to ensure continuous

Pacific Oceans. These satellites provide permanent surveil¬

beacon location. It was only in 1988 that COSPAS—SARSAT

lance but cannot use the Doppler effect to locate distress bea¬

was declared operational and a permanent management

cons since they are fixed relative to the Earth. Positions can be

organisation set up. At the same time, an agreement within

ascertained if they are encoded into the message from the

the framework of Inmarsat established a dedicated search

beacon, provided that the beacon is capable of calculating its

and rescue satellite system, integrated into the Global Mar¬

position via the GPS system, or they can be derived from the

itime Distress and Safety System (GMDSS).

LEOSAR system, with possible delays.

Since then, 24 other countries have become members,

At the beginning of the year 2000, 250 000 beacons used

including Norway, the United Kingdom, Finland, Bulgaria,

the frequency 406 MFIz for uplinks to GEOSAR and LEOSAR

India, Sweden and Italy, committed to providing the Earth-

satellites, and 600 000 beacons exclusively used the fre¬

based components of the system. Between 1982 and the end

quency 121.5 MHz for uplinks to LEOSAR satellites, a fre¬

of 2000, the system helped to rescue more than 11 000 peo¬

quency scheduled for withdrawal in 2009.

ple, mainly at sea. Like Argos, the system uses one-way communications,

DORIS

beacons being activated either inertially upon impact, by

DORIS (Doppler Orbitography and Radiopositioning Inte¬

immersion, or manually when this is possible. Today it is

grated by Satellite) was developed by French organisations

made up of two complementary systems, LEOSAR and

(the

GEOSAR. LEOSAR uses low-Earth orbiting American NOAA

Recherches Geodesiques et Spatiales GRGS and the Institut

satellites and Russian Nadezhda satellites whose relatively

Geographique National). It is designed to make accurate deter-

150°

French

space

agency

CNES,

120°

the

120

Groupement

I 20

Arctic circle Arkhangels] Churchill

loscow

Edmonton Mtenton California

® Hawaii ® Guam Manaus Jakarta

• Recife

Santiago Cape Town

Albany

Wellingti

Arenas

Antarctic circle

• Stations receiving LEO satellites LEOSAR local coverage

GOES-East coverage GOES-West coverage

Insat-2 B coverage

Figure 11.12. The COSPAS-SARSAT stations. Regions covered in 2001 by the network of ground stations where distress signals can be immediately relayed by satellite.

de

»

Systems using uplink signals

150°

120°

90°

60°

30°



30°

60°

90°

120°

150°

Ny Aalesund ®

Murmansk Arctic circle 0 Fairbanks

^Yellowknife

Reykjavik ®

0 Metsahovi

60°

Krasnoyarsk 0

Yuzhno-Sakhalinsk Toulousew

Goldstone 0

Dionysos

0

Santa Maria •

30°

Badary

*

Ottawa

Kltab •

. Richmond

Purple Mountain

m

Everest i

. Kauai Socorro Island 0

k Arlit

Dakar

Djibouti'

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Colombo i

Manila

0 Guam

Libreville 0 Ascension

0

St Helena Wallis 30°

Arequipa 1

# Papeete

0

Rapa

0



Cibinong

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Easter Island Santiago •

0

0

Darwin

Hartebeesthoek

► Port Moresby

0

0 la Reunion

0

Noumea ’ Yarragadee Orroral'

Tristan da Cunha

0 Amsterdam

Marion Island

0 Kerguelen Rio Grande 60° Rothera

Syowa

0

Dumont d'Urville Antarctic circle

Figure 11.13. The DORIS permanent beacon network.

minations of orbits and to localise beacons. Satellite orbits are

Once

the

orbit has

been accurately

determined, it

precisely calculated by measuring the Doppler shift at two fre¬

becomes possible to find the position of a beacon, already

quencies (400 MHz and 2 Ghz) transmitted by ground sta¬

localised to within a few kilometres, with accuracy better

tions. Two frequencies are used in order to reduce the error

than 10 cm relative to the three axes of a geocentric world

introduced when the signal propagates across the ionosphere.

reference system, using the approximate location of an asso¬

The system requires a network of about 50 orbitography bea¬

ciated Argos beacon if need be.

cons, evenly distributed across the surface of the planet. These

Coupled with onboard software capable of real time

transmit signals to the satellite whose position is to be deter¬

orbital calculations, DORIS can be used for autonomous

mined and can achieve accuracies of the order of 10 cm. The

satellite navigation. In this capacity, it even provides an alter¬

DORIS device has been successively carried by the SPOT 2,

native to GPS when establishing relative positions within

SPOT 3, and SPOT 4 satellites, as well as theTOPEX-POSEIDON

constellations. This has led to increased interest in the system

satellite. In the latter case, it was able to calculate the orbit to

on a European and international level (fig. 11.13).

within about 2 cm, a quite exceptional radial accuracy. It will be carried aboard both Jason and Envisat 1.

331

Chapter Twelve



Status OF MILITARY ACTIVITY

»

Collection of information

» Telecommunications ■



SPACE: THE NEW BATTLEFIELD?

Status of military activity

Military satellites, whose existence was for a long time offi¬

applications. According to most other interpretations, how¬

cially denied, are often referred to by the general public as

ever, only offensive military activities are thereby ruled out.

spy satellites. This term, which only identifies the category of

The Agreement governing the activities of States on the

surveillance satellites, does immediately raise a question con¬

Moon and other celestial bodies, or Moon Treaty, put forward

cerning the legitimacy of military uses for space (fig. 12.1).

for signature in 1979, would eventually confirm this looser

The treaty ‘on principles governing the activities of states

interpretation, specifying that activities must be of an exclu¬

in the exploration and use of outer space, including the

sively peaceful nature, but that the use of military personnel

Moon and other celestial bodies’ remains the basic reference

or equipment is not forbidden, provided that it serves only

for such questions. Often referred to as the Outer Space

peaceful purposes. For various reasons, however, this agree¬

Treaty or the 1967 Treaty, this first great treaty recognises ‘the

ment was signed by very few countries. Military satellites are

common interest of all mankind in the progress of the explo¬

therefore allowed to exist insofar as the expression ‘peaceful

ration and use of outer space for peaceful purposes’.

purposes’ is understood to be the antonym of ‘aggressive

As far as international treaties go, this one was drawn up at

purposes’. The ambiguity remains and practice has only

very short notice. Furthermore, since there was no possibility

strengthened the position of military users. Over the last

of referring to common practice, the 1967 Treaty is charac¬

30 years, a considerable number of military satellites have

terised by a much more liberal attitude than can be found in

been sent into space, and countries other than the United

corresponding treaties overseeing maritime or airspace law.

States and Russia now possess military space capabilities,

This approach was strongly upheld by United States repre¬

although sometimes limited, or their own programmes.

sentatives on UN committees responsible for setting out the

Nevertheless, even if it is accepted that ‘peaceful’ can be

treaty, but initially met with opposition from a great many

taken to mean ‘non-aggressive’, the dividing line between

countries still lacking in any space capabilities. These coun¬

offensive and defensive uses of a space system is also rather

tries saw themselves irredeemably condemned to second

poorly defined. Observations may serve to prepare an attack

place with respect to the space powers. For its part, the Soviet

just as they may serve to warn of one, and navigation-

Union also expressed concern over the American position.

positioning systems could be used to improve the accuracy

In fact, a question of sovereignty is raised with regard to territories overflown by satellites. The particular technical

334

of a missile just as effectively as they could locate a vessel in difficulty.

constraints that affect satellite orbits in space (see Chapters 2

Among existing military space systems, it appears that

and 3) mean that any non-geostationary satellite must by def¬

many military satellites fulfill very similar roles to their

inition fly over every region of the Earth’s surface with lati¬

civilian counterparts, i.e., scientific, telecommunications,

tude less than the inclination of its orbit (see Chapter 3). In

weather, observation, and navigation satellites. They do

addition, the fact that the Soviet Union was unable to prevent

include certain rather particular technical specifications,

satellites from flying over its territory and their tacit accep¬

often of a defensive nature, such as satellite and data protec¬

tance of this state of affairs, as witnessed by their participation

tion systems, or else they satisfy rather specific operational

in the International Geophysical Year, and even more clearly

requirements. Other missions are exclusively military in aim,

by the precedent set by sending Sputnik into orbit, rendered

but may help to stabilise relations between countries. Exam¬

further opposition to the principle impossible. The idea of

ples are the early warning systems set up in the context of

defending national interests therefore had to be weighed

nuclear

against more practical considerations. Those upholding the

designed for times of crisis. Alongside this first category,

sovereign rights of states only obtained the guarantee that no

other uses have been at least tacitly admitted, characterised

weapons of mass destruction would be allowed, and an oblig¬

by a potentially offensive capability. These include antisatel¬

ation to use space for peaceful purposes.

lite and antiballistic missile systems (ASAT and ABM), or

dissuasion,

or

electronic

intelligence

systems

The absence of any real consensus and the desire to find a

more symbolically at the time, the US Strategic Defense Ini¬

compromise are clearly apparent in the ambiguity of the

tiative referred to as Star Wars, and today the National Missile

final text, which remains open to a wide range of interpreta¬

Defense (NMD). In the latter cases, only the claim that they

tions. According to a strict reading, the term ‘peaceful’

serve a dissuasive purpose can be invoked in their support.

excludes all military use at the outset. This is the position still

Since the beginning of the 1990s, a new dimension has

adopted today by India, for example, which considers that

been introduced by satellites carrying both military and civil¬

‘peaceful purposes’ can by definition only concern civilian

ian capabilities, as described by the terms dual-use or dual-

Status of military activity

purpose. One example is given by localisation and navigation

trend has been confirmed by a proliferation of programmes

systems considered separately (Chapter 11). Military satellites

treating space as a potential battle field. At the same time, the

are recognised as force multipliers and, through the develop¬

basic principles of unrestricted use, and even free access to

ment of civilian applications, have come within reach of an

space by all states, have been tacitly questioned. In the com¬

increasing number of countries. In such conditions, finding

ing decades, this evolution in the fundamental principles

itself to be the only significant military space power remain¬

controlling military use of space, encouraged by some, whilst

ing after the collapse of the USSR, the United States considers

being perceived as a destabilising factor by others, may well

that space has become a key element in its national security

embody one of the main changes in space development.

and that all possible risk must be excluded. The concept of

New states, in particular certain European countries, have

‘space control’ has thus become fundamental. The idea that

expressed the intention of acquiring their own means of sur¬

satellites could guarantee peace, originally put forward to

veillance in a world context plagued by instability. The rela¬

justify the existence of military satellites, was transformed.

tive strengths of the space powers are therefore likely to

The American position as world peace-keeper was sufficient

undergo a gradual transformation, with the United States

to sustain the kind of monopoly envisaged. This reversed

confirming its current role as world policeman.

Figure 12.1. Image of a Soviet shipyard taken by an American military reconnaissance satellite.

i

335

Collection of information

from space, since they could more readily obtain information from other countries using quite traditional means. Nikita Khrushchev immediately threatened to shoot the satellites down, together with any U2 spy planes, before choosing to develop his own space-based observational capability in the form of the Kosmos 4 satellite, launched in 1962. Reconnaissance satellites constitute the largest category of military satellites, from a purely numerical point of view. The main families are the American Key Hole satellites (KH) and the Soviet, then Russian, Cosmos satellites. There are several types of spacecraft, whose characteristics have evolved with technological advances and also with changing mission objectives. The latter range from strategic and tactical obser¬ vation to checking that disarmament treaties have been respected, and assessing conflict damage. In 1995, first Israel and then France, in cooperation with Spain and Italy, broke the Russian-American oligopoly that had stood for more than 35 years. In 2000, following a mod¬ est incursion with its FSW recoverable capsule programme, China launched its first photo-reconnaissance satellite returning data to ground stations digitally. ZiYuan 2, which means ‘resources’, very probably uses the China-Brazil Earth Resources Satellite bus (see chapter 9), known also by the Chinese as ZY 1. Launched at 500 km altitude, the satellite

Amongst the wide range of space vehicles accomplishing military missions, a great many satellites are concerned with surveillance missions, such as high resolution observation, detection of nuclear explosions, early warning in the event of ballistic missile launch, maritime surveillance and com¬ munications monitoring. Although both the United States and the Soviet Union developed the same type of system for gathering military information, deeper analysis reveals different strategies in line with their differing national capabilities and the role they hope to play on the international stage. Since the begin¬ ning of the 1990s, the faltering Russian economy has led to a blatant imbalance between the United States and the rest of the world, despite the appearance of new actors whose mod¬ est capacities nevertheless counter the threat of total Ameri¬ can hegemony. Reconnaissance satellites Earth observation was first developed for military reasons. Satellites offered an unexpected opportunity to acquire strategic information from poorly accessible regions. The American experimental reconnaissance satellites Discoverer and SAMOS were launched as early as 1959, whilst the Sovi¬ ets remained hostile to the idea of unrestricted observation

I960 l O 1 2

0 4

I 0 6 8

1965

• 9 13 0 2

KH-1

4

• • •# * i

1970

••• •

KH-2

KH-3



KH-4

Corona Programme

• o» ••••*•••• • ••• '•••••••••• •••• 4 5 6 9 1215 18 20 3

24 27 30 33

7 101316 1922 25 28

35

3134

• ••••••• i •

38 40 42

37 39 41 4c

•••• • •

8 111417 21 2326 29 32 36

KH-4B ' • m

Argon KH-5

Z

3

5

6 7

8

8

121314

910

• • • • • • • • • • i • • • « 21

6 8 1012 14 16 19 17

20

24 27 30 33

22 25 28 31

34

23 26 29 32

Gambit Follow-On KH-8 * * !

W ?2 11 13 15 17 19 21

24 f5 23

27 26

% % S. *2

?3

S?5

^

*7

I

44

6 • 7

* 9

* 11

France Figure 12.2. Chronology of reconnaissance satellites. (United States, Israel and France)

46

13

Kennan / Crystal KH-11 i

810

45

28

Hexagon (Big Bird) KH-9A SAMOS

Israel

336

910 11

••

Lanyard KH-6 1 j S Gambit KH-7

Known lifetime Unknown lifetime (nominal lifetime indicated by length of line)

Oko-2 (GEO) 775«

Collection of information

and Italy is open to new participants and Belgium, Sweden and Austria have expressed their interest in 2002.

Following two experimental satellites, the deployment of Offeq 3 in 1995 marked the beginning of a novel pro¬

The Helios system is fairly close to conventional military

gramme aimed at space-based military observation of just

reconnaissance systems, although it has developed in a rather

part of the Earth’s surface, motivated by regional rather than

novel way. Indeed, it breaks with a hitherto undisputed tradi¬

worldwide geostrategic considerations. With limited finan¬

tion whereby civilian satellites were invariably subordinate

cial resources, they had to face significant physical con¬

to their military counterparts. Experience acquired through

straints. The location of the Palmahim base means that

the civilian programme SPOT (platform, CCD sensor tech¬

satellites can only be launched into retrograde inclinations, if

nology, on-board recording techniques and digital data

Arab territories are to be avoided during the launch phase.

transmission systems), combined with a genuinely profit-

This is also a disadvantage for the launch vehicle, which was

orientated financing, show that another logic is perfectly fea¬

developed for the Jericho missile programme and has only a

sible, in which military capabilities derive from civilian ones.

limited launch power (see chapter 6). The Offeq 3 satellite,

Other countries in possession of civilian remote-sensing

with a mass of 225 kg at launch, and a 36 kg payload, was

satellites, such as Japan, India and China, may also be

placed in an orbit with apogee at 369 km in such a way as

tempted to follow the same line, provided it falls in with

to cover a region lying between latitudes 30° north and

their political outlook. At the same time, the case of the

30° south. The launch of Offeq 4 in 1998 was to bring

Israeli satellite Offeq demonstrates that small satellites result¬

marked improvements to the system, still operating in

ing from relatively simple technological developments can

optical mode, with resolutions down to about one metre.

also fulfill certain fairly limited requirements with regard to

However, it failed and the launch of Offeq 5 is expected for

the pressing concerns of national security.

2002 (seefig. 12.2).

1985

1990

2000

1995

10 ■ 121 13 >

DSP 3rd generation (GEO)

14'

19*

1518

20»

< 1569 ' 1806 1

1547

1922'

1

1596 1785

1409 i 1793 ■ 2368 « 1586

lation 6 2196 1

261—■

lation 7

2084 ■ 2087 1

1278 “

2176 ' 2340

lation 8 1966

1317 • 1701"

lation 9

j

1903 1

1367 ■

2105'

1604 >

2217 •

1783 1

1629*

Prognoz (GEO) 2209 2224 1 2282

1

343

344

)

Military applications of space

The appearance of new metre-resolution commercial pro¬

ously been carried out by the Vela family within the frame¬

jects (see chapter 9) has introduced a new element into the

work of the 1963 treaty banning nuclear tests in the atmos- „

problem, even though three fundamental features, the

phere and in space. These were in turn succeeded by the DSP

degree of control entrusted to users, continuity of data

satellites (Defense Support Program), the name being attrib¬

acquisition, and data transmission times, make all the differ¬

uted in 1976. DSP combined alert and detection of nuclear

ence with a military system. The Israeli-US programme

explosions (fig. 12.4). In 1991, two of the five geostationary

EROS, launched in December 2000, forms part of this new

DSP satellites were reserves, clearly illustrating the impor¬

logic. The situation may be even more complex in the con¬

tance of this mission for the American government. The DSP

text of an officially dual-use programme, i.e., a programme

system has since undergone many improvements. The first

devoted to both civilian and military objectives, as in the case

concerned data relay with the Talon Shield programme,

of the Japanese Information Gathering Satellite (IGS). This

implemented in 1996. This programme was entrusted to a

option was chosen when North Korea launched its missile

specially created military unit, and mainly consisted in sim¬

Taepo Dong in November 1998. The tendency to use Ameri¬

plifying the procedures and stages involved in relaying alert

can technology shows how far most countries still depend

data. To this end, data reception, processing and retransmis¬

on the main space powers, but it does not rule out the possi¬

sion to units based abroad were centralised at the US Air

bility of subsequent autonomous development. The same

Force base on Cheyenne Mountain in Colorado. Eventually,

trend can be observed in South Korean or Taiwanese projects,

specially equipped vehicles will be sent to future operational

also involved in the technological development of small

theatres to receive satellite data directly. Often better known,

satellites (see chapter 4). The launch in October 2001 of the

the second phase of this modernisation programme concerns

experimental Indian satellite TES (Technology Experiment

the satellites themselves. As part of the SBIRS warning pro¬

Satellite) with one metre resolution indicates a new military

gramme (Space Based InfraRed System), improvements in

interest for officially civilian programmes

satellite performances (see fig. 12.11) now take into account the threat of medium range ballistic missiles. Two features

Early warning satellites

must be improved in consequence. The first is infrared detec¬

Whereas observation satellites are today being used by an

tion of short range missiles in the atmosphere, which is not

increasing number of countries, early warning systems belong

yet adequate, as witnessed by difficulties encountered in the

to much more restricted circles (fig. 12.4). Their mission is

1990 Gulf War. The second is the frequency with which data

closely bound to the question of nuclear dissuasion. With the

is collected. At the present rate of once every ten seconds for

development of Soviet intercontinental missiles at the end of

DSP satellites, the trajectories of these missiles, propelled for

the 1950s, one of the primary concerns of the United States

much shorter periods than intercontinental missiles, cannot

was to set up a network of early warning satellites. Their task

be correctly ascertained.

was to provide rapid information about the launch of ballistic

Beyond such improvements, new categories of satellites

missiles. By overcoming the obstacle posed by the Earth’s cur¬

should see the light of day in the period 2004-2010. Two

vature, the best systems were able to double the warning time

further early warning satellites are planned for highly ellipti¬

as compared with Earth-based radar systems, extending it to

cal orbits that will provide coverage of the North Pole. These

around thirty minutes. The long series of satellite families is

satellites are intended to supersede infrared detectors proba¬

witness to the many technical problems encountered in

bly carried on board the Jumpseat intelligence satellites, in a

designing and gradually improving these alert systems.

similar orbit (Heritage programme). Perhaps more signifi¬

The MIDAS satellites (Missile Defense Alarm System),

cant, an as yet undetermined number of low-orbiting satel¬

deployed in circular polar orbits, were originally equipped

lites should complete the US defence panoply. Their main

with infrared sensors designed to detect heat emissions pro¬

task would be to provide precise determinations of reentrant

duced by missiles during their combustion phase. However,

enemy missile trajectories for the purposes of exo-atmos-

it proved difficult to restrict identifications to the phenome¬

pheric interception. If detector performances are adequate,

non in question, with other natural factors likely to interfere,

other missions could be envisaged for these satellites, such as

such as the reflection of the Sun’s rays from high altitude

the detection and characterisation of shots fired on the batde

clouds. In order to reduce the number of false alerts, televi¬

field (technical intelligence). This component would be a

sion cameras were also carried on board. Later, their succes¬

fully integrated into the kind of tactical intelligence imag¬

sors followed circular orbits at an altitude of 36 000 km, but

ined for the years to come, that is, based on ever closer cross

with inclination close to 10°, to provide improved coverage

referencing of the complete data set gathered by satellite,

of the high latitudes where Soviet missile launches were

including visible and infrared data, signal analysis, remote

based. At the beginning of the 1970s, the IMEWS system

sensing, intelligence and so on (see fig. 12 11).

(Integrated Missile Early Warning Satellite)

marked the

beginning of a new phase. These satellites were placed in geo¬

Soviet systems took much longer to set up. This was partly

stationary orbit and simultaneously provided early warning

due to technical problems in developing an infrared system,

and detection of nuclear explosions, a task that had previ¬

but political choices undoubtedly played a part in the delay.

Collection of information

|

The first genuine early warning system was not established

Electronic intelligence satellites

until the second half of the 1970s, and even that was some¬

These satellites, often called ELINT (Electronic INTelligence),

what limited. After deploying the first Oko satellites on Mol-

are designed to listen in to communications, whether they be

niya orbits (fig. 12.4), the full constellation comprising nine

military or otherwise, in order to obtain information about

satellites only became operational in 1987. Since 1989, sur¬

the size, deployment and level of readiness of enemy forces.

veillance by non-geostationary systems has been comple¬

This mission is known as COMINT, which stands for COM-

mented by the Prognoz geostationary satellites.The existence

munication INTelligence. Within the context of another activ¬

of such systems was only officially recognised in 1993, even

ity known as SIGINT (SIGnal INTelligence), they also serve to

though the corresponding positions on the Clarke orbit had

locate anti-aircraft and antimissile radars, identifying their

been reserved under this name at the ITU (International

frequencies with a view to neutralising them by suitable

Telecommunication Union) since 1981. In 1992, two satel¬

countermeasures. All these parameters, under the command

lites were launched, followed by one more each year, but this

name of battle intelligence, are continually monitored in

would not appear sufficient to maintain the whole system.

peacetime in order to give immediate warning of any

Difficulties encountered by certain Prognoz satellites com¬

unusual activity. In time of crisis, the aim is to obtain a clearer

bined with inadequate replenishment of the Oko satellite

assessment of the real intentions a potential enemy may have,

constellation have continued to limit present Russian capa¬

and in time of war, to identify the type of attack under prepa¬

bilities (fig. 12.5).The changing strategic environment, par¬

ration and thereby set up appropriate countermeasures, such

ticularly with regard to the United States, explains why this

as jamming of enemy communications.

warning programme is no longer a priority. The inability of

ELINT satellites, launched by the United States since 1961

Russian defence to finance new systems better suited to

and five years later for the USSR, thus have an essential part to

countering the threat of medium range ballistic missiles is a

play in information gathering (fig. 12.6). Little is known

clear sign of their gradual decline as a military space power.

about these programmes, and what there is generally comes

At the same time, US development of the NMD programme

from indirect sources. Soviet systems are mainly identified

has led to a new appreciation of Russian needs. Efforts have

via orbital parameters.These systems, invariably going by the

been made to maintain a minimal capacity and since 1998

name of Cosmos, are all officially referred to as scientific

there has even been a certain degree of cooperation with the

satellites, even though no results have ever been published.

United States in the guise of the RAMOS research pro¬

The appearance of the first prototypes as early as 1967 shows

gramme (Russian AMerican Observational Satellite).

that ELINT satellites, together with photographic reconnais-

Prognoz Satellite :

■ permanently occupied position

■ intermittent position

Oko Satellite :

• position at closest apogee to Moscow

^

J

-Orbital track

permanent and intermittent coverage

J

_

Coverage

Figure 12.5. Russian early warning satellites. Trajectories and surveillance zones. In 2000, the four Oko satellites were operating but the Prognoz positions did not appear to be occupied by any active satellites.

345

346

Military applications of space

sance satellites, were granted political priority. Satellites

the lifetime of these satellites remains relatively short. Since

launched in the 1980s belong to the third and fourth gener¬

the second half of the 1980s two constellations ofTselina

ations, and appear in considerable numbers. This can be

satellites (Tselina D and 2) have been exploited in parallel.

explained by the preponderance of non-geostationary satel¬

TheTselina 2 system, apparently designed to cover the whole

lites, with the task of providing global intelligence almost in

ELINT mission, is still being deployed. Launches continue,

real time. Furthermore, although in constant progression,

although at an ever reducing rate since 1992 (between one

Figure 12.6. Chronology of ELINT and ocean surveillance satellites.

1960 "Heavy Ferrets”

1975

1970

1965

NOSS precursor

11 2

NOSS (PARCAE) and 3 subsatellites

(500 km, 75 to 80°)

(1100 km, 63.5°)

Subsatellites "Ferret (LEO, 80 to 107°)

(A

0)

Subsatellites "ferret"

Canyon (USAF) (quasi GEO)

= Chalet-Vortex (USAF) (GEO)

RhyoliteAquacade (CIA)

1' 3*4"

(GEO)

Tselina-D

(Numbers are those assigned to satellites in the Kosmos series)

(630 km, 81.2°)

Tselina-0 (540 km, 74°

389 405 ■

542 '

250

269

808 «

436 « 437 460' 479 i 500

Ocean intelligence satellite

o:

Ocean radar satellite

c

Failure

895" 925" 955"

425 r

Electronic intelligence subsatellite

Ocean intelligence subsatellite 582 « 610 « 631 * 655 * 661** 698 * 707 *

© Known lifetime

os «)

3

851"

387"

Electronic intelligence (Elint) satellite

(A (A 3

604 i 673 '

200 1 315 ' 330 '

re

476 i

781 * 787" 790 * 1008 » 812* 1062* 845* 870 ■ 899 924 ■ 960"

Unknown lifetime (nominal lifetime indicated by length of line)

EORSat

699

777

838

868

937 •

(410 km, 65°)

RORSat (250 km, 65°)

198 ~2o9 •

367 *

402 ■

469 ■

516 «

626 « 651 * 654 «

723 ■» 724 * 785 «•

860 1355 1405 76 .1249 1365 mmm 1266> 1372 * 1299 ■ 1402 — 1412 ■

1769 1507 -

1567 --— --- --1588 --— 1646—— 1682 1735 1579 — 16075

2060 1834:1890 — 1949

1979 2033 2046 2051

2264 2096-=2103 • 2107 2122

2293. 2313 2326

2238 2244 2258

2335

2347

2347

17361670 ■ 1677 < Cerise (experimental) Clementine (experimental) 1

347

348

|

Military applications of space

half of the 1970s, today form the main constellation. It is

context of the Space Based Wide Area Surveillance (SB-WASS)

complemented by satellites in highly eccentric orbits, like

programme, a long debate was fought out over whether the »

the Jumpseat series. These are used to listen in to high lati¬

sensors should be infrared or radar. The result of these discus¬

tude regions and also the Soviet Molniya telecommunica¬

sions is not precisely known. However, launches carried out

tions satellites in the same type of orbit. In the United States,

during the first part of the 1990s, involving various Singleton

the increasing multiplicity and complexity of electronic

or Triplet type satellites, would seem to suggest a compromise.

sources under investigation may lead to the implementation of a combined architecture for intelligence and signal analy¬

New openings for global surveillance

sis. This would bring together all the components so far

The United States is now perfecting and increasing the num¬

developed in a single set of low-orbiting satellites better

ber of programmes designed for tactical surveillance of the¬

suited to intercepting a wide spectrum of data. It seems that

atres of war. These new technical capabilities should give the

one such project, designated IOSA 2 (Integrated Overhead

US military better information concerning their enemies in

SIGINT Architecture), is currently under study at the

every situation and in any weather. One particular aim is

National Reconnaissance Office.

improved tracking of moving targets on the ground, often

Among the space powers beginning to build up military

difficult to locate and almost impossible to track by tradi¬

capabilities, France has developed two experimental satel¬

tional spaceborne means. Lessons learned in the Gulf War,

lites, Cerise in 1995 and Clementine in 1999, launched at

and in subsequent conflicts in ex-Yugoslavia, have led Amer¬

the same time as the reconnaissance satellites Helios 1 and 2.

ican strategists to think about extending the use of satellite-

Only the second is actually operational. A swarm of Comint

based radar surveillance, making it a key element in all future

microsatellites (ESSAIM programme) is scheduled for 2004,

space-based information gathering systems.

but these will only provide warning signals in times of crisis.

These new needs have been invoked to justify financial backing for new radar satellites, possibly to be used in a con¬

Ocean surveillance satellites

stellation. Hence, the main objective of the American pro¬

Chronologically speaking, ocean surveillance constitutes the

gramme Discoverer II, run jointly with the US Air Force,

third main sector of spaceborne military activities. The great

DARPA, and NRO, is the tracking and global surveillance of

number of Soviet satellites expresses their particular desire to

military targets. This programme is a continuation of the

track naval units, a key component in US and NATO forces.

Starlite project (Surveillance, TArgeting and Reconnaissance

The Rorsat programme thus consists in carrying out radar

SatelLITE) launched in

1997 by the Pentagon research

surveillance from low orbits, at altitudes around 250 km,

agency. It would use 24 satellites in low orbits, equipped

given the energy requirements of radar systems. This is the

with radars called Ground Moving Target Indicators (GMTI),

name attributed to it by the Western world, an allusion to its

which can detect and follow moving targets, and synthetic

mission (Radar Ocean Reconnaissance Satellite), although

aperture radars capable of high resolution imaging and high

the Russian code name may well be USA. Intelligence

precision numerical data acquisition concerning ground ele¬

obtained by the Eorsat system (Electronic Ocean Reconnais¬

vation. One of the main tasks of the programme is to be able

sance Satellite) - or USP according to the Russian name -

to revisit any zone between latitudes 65° north and 65° south

from an orbit at 400 km, but with the same inclination of

within just 15 minutes. In February 1999, a first study phase

about 65°, was originally designed to complement this radar

was granted to a team made up of three manufacturers

detection. In fact, technical difficulties in developing the

(Lockheed—Martin, TRW and Spectrum Astro) for platforms

nuclear reactors intended to supply Rorsat’s energy needs

weighing between 1000 and 1500 kg at costs below 100

have led to at least a temporary discontinuation in the pro¬

million dollars each. The schedule includes a test period in

gramme. There has been a corresponding increase in the

orbit extending from 2003 right through to a fully opera¬

strength of the Eorsat programme, which varies between

tional deployment expected for 2007. Even if the manufac¬

four and six satellites distributed in two different planes.

turers keep to these deadlines, this does not mean that the

The US ocean surveillance system has long been made up

project will be carried out in its entirety. Its cost and com¬

exclusively of the White Cloud satellites, also called NOSS after

plexity remained the subject of much controversy in 2000.

the name of the programme they belong to (Naval Ocean Sur¬

The lack of consensus on this point may lead to the pro¬

veillance System). The system usually comprises a main satel¬

gramme being abandoned in its present form, although there

lite and three subsatellites, all orbiting within a few hundred

seems to be agreement that radar surveillance is needed.

kilometres of one another. Boats are then located by triangula¬

In parallel with this, the warning and detection system

tion, and identified by analysing emitted signals. Five primary

SBIRS has also undergone studies aimed at increasing the tacti¬

and secondary systems are theoretically operational at the same

cal potential of infrared detection, in addition to the localisa¬

time, from an orbit at altitude 1000 km, and inclined at 63°.

tion of ballistic missile launches. Going beyond considerations

Several complementary satellite projects have been studied,

of new programmes, efforts are also being made to improve

in particular by the US Marines and Air Force, with a view to

the way these systems work together. In the longer term, a

wider ocean surveillance. At the beginning of the 1990s, in the

genuine architecture for global surveillance may be the result.

Telecommunications

Satellites have become an essential tool for conducting mod¬

be more especially designed to provide long range commu¬

ern military operations and responding to a wide range of

nications and gather information from low power transmit¬

crisis situations. By providing links between units in the field

ters, storing them for subsequent relay to ground-based

and the command centre, or transmitting data from a recon¬

stations, very often almost in real time.

naissance satellite in almost real time, satellites play the role

The whole range of telecommunications links is provided

of force multipliers, overcoming the usual terrestrial con¬

by three main types of closely integrated system (fig. 12.8).

straints, particularly in inaccessible or uncontrolled regions.

Most of these low-orbiting satellites, referred to as Strela satel¬

American telecommunications satellites thus handle around

lites, are launched at altitude 1500 km and inclination 74°.

three-quarters of all long distance military links, and cable

They are launched in clusters of eight small Kosmos satellites,

plays a rather complementary role, increasing security by

some of which are still operational. They are complemented

diversifying the means available. The huge diversification in

by a constellation of slightly heavier Kosmos satellites,

information sources and the need to integrate the resulting

launched individually. The first three of these were positioned

data are a further spur to developing such systems, and it has

at altitudes 780-810 km, and inclinations of 74°, moving in

become impossible to imagine military activity taking place

three orbital planes at angles of 120° to one another. Finally,

without them.

since 1985, a new system of satellites has been launched in

The increasing role of geostationary satellites in telecom¬

clusters of six in two orthogonal planes at altitude 1400 km

munications activities does not mean that other types of

and with an inclination of 83°. It would appear to be destined

orbit are likely to disappear (fig. 12.7).

to supersede the first generation with its clusters of eight

Various arguments support the use of such systems. The

satellites. The Raduga and Potok satellites (as they are called

first is of a geographic nature, since non-geostationary satel¬

when reservations are made at the ITU) complete the panoply

lites are the only ones capable of covering zones at latitudes

of Russian military space telecommunications systems. The

above 70°. The most common are the Soviet, then Russian,

launch in 2000 of a new Russian Geyzer relay satellite shows

Molniya satellites, with a very characteristic orbit providing

that new systems continue to be implemented, despite delays.

civilian and military links from the Baltic to the Pacific, over

US non-geostationary systems only include military satel¬

a complete range of services extending from telephone to

lites in the IDSCS and SDS series. The first satellites in the Ini¬

television.The SDS satellites (Satellite Data System), transmit¬

tial Defense Satellite Communication System appeared in

ting US communications to and from their Arctic military

1976, in the plane of the equator but at altitudes slightly

bases, have tire same type of orbit.

below the geostationary orbit.The whole constellation there¬

Moreover, from a purely economic standpoint, these satel¬

fore drifts on a daily basis, thus allowing coverage even if one

lites can be lightweight, launched in clusters or together

member should fail. The advantage of this system was to pro¬

with a heavy payload, when the launch vehicle places several

vide security at a relatively low cost. It provided long range

instruments in orbit. This further reduces the overall cost of

tactical communications (up to a maximum of 16 000 km)

such missions. These light satellite systems have always been

and transmission of high resolution images.

preferred by amateur radio enthusiasts.

American satellites in the SDS family have highly eccentric

Most non-geostationary satellites in operation are Russ¬

orbits and have often been launched at the same time as

ian, generally in low circular orbits, but with eccentric geo¬

reconnaissance satellites in the KH series. Indeed, they long

synchronous and geostationary orbits since the end of the

provided the downlink for the KH satellites. Initially carried

1980s. Confusion between civilian and military activities, a

out by two satellites better known by the name of Jumpseat,

traditional feature of Soviet, then Russian, space operations,

the last two of which were launched in February 1987 and

makes it difficult to determine exactly what mission a given

November 1988, these missions were gradually transferred

constellation is intended to achieve. However, it would

to NASA’s TDRS (Tracking and Data Relay Satellites) in geo¬

appear that the most diverse services, ranging from tele¬

stationary orbits. This type of system involves considerable

phone, through governmental and military communications

savings and small satellite projects of the Lightsat type, which

to television, are guaranteed by Molniya satellites.

became fashionable again in the 1980s, are close to the orig¬

Low circular orbits tend to be reserved for the needs of the

inal idea behind IDSCS.

military and in particular for direct tactical communications

As for other military applications, future satellite communi¬

linking military command centres on national territory with

cations systems should have quite different designs from exist¬

ships, aeroplanes and ground units. Some satellites seem to

ing systems. New trends in this domain follow two main lines.

34$

350

|

Military applications of space

1958

1975

1970

1965

1960 STRELA-1 (inclination 56°)

STRELA-1M (octets) (circular orbit at 1500 km inclination 74°'

(Numbers are those assigned to satellites under the name "Kosmos")

(Numbers are those assigned to satellites under the name "Kosmos")

(test) 236*

STRELA-2

(Numbers are those assigned to satellites under the name "Kosmos")

(circular orbit at 800 km inclination 74°)

292* 304

614 332

372 407

37 ■

MOLNIYA-1

MOLNIYA (excentric orbit 600 / 39 000 km inclination 63°26)

MOLNIYA-2 (K 837, 853)-

IDSCS

17

(circular orbit at 33 900 km inclination 0°)

LES

845

16-18 *

5=

(circular orbit from 33 300 to 35 800 km inclination 0 to 25°)

DSCS-II (geostationary orbit)

1-2!

3-4 1 7-8:

5-6«

satellites : Soviet, then Russian US NATO

FleetSatcom

UK

(geostationary orbit)

Failure Known lifetime Unknown lifetime

(nominal lifetime indicated by length of tine)

NATO (geostationary orbit)

Skynet (geostationary orbit)

Figure 12.7. Chronology of military telecommunications satellites.

Telecommunications

1980

1985

1990

1995

2000

92-99 1228-35 ■ 1250-57 1287-94 ■■§

1320-27 1357-64 1388-95 _ 2197-2202 _2211-16 2090-95 22252-57 2143-48 MBB 2268-7 2157-62 2038-43

1994-99

STRELA-3 (sextets) (circular orbit at 1400 km inclination 82°6)

1827-321

Gonetz-D 1-3 (civilian)

2337-39^

Gonetz-D 4-6 (civilian)^

2352-57 I 3 Gonetz-D and 3 St re I a9

1269 1331 11

1420

1538 1814 1624"

17701

.1503.

2056

1741"_*U££« 1850"



2208

1954

55 1 74"

47-

53" 64" (K 1423) *

59'

67 1

58" 71" 66" 60" 52"

73"

77 ■ 80 ■

69" 82 '

57-

79 ■

85 1

orbit) Kosmos 1366

1 (OO

SDS advanced version ? 1' Capricorn 1 SDS 4 niya orbit) Microsat-1 d 7

16 '

DSCS-III 1 (geostationary orbit)

(geostationary orbit)

4 3' UFO (geostationary orbit) i*

2‘

Milstar (geostationary orbit) 1 ■

!

351

352

|

Military applications of space

17 billion dollars in all) testify that it was originally planned with nuclear war in mind. At the same time, a global restruc- turing of existing means in other frequency bands is cur¬ rently underway. It is particularly concerned with the 7.2-8.4 GHz range, used until now by the DSCS satellite series (Defense Satellite Communication System).This family has been the subject of constant improvements. Examples are the appearance in 1982 of the third generation DSCS III satel¬ lites (also carrying a UHF capability), or the current DSCS development programme which rests upon improvements in the tactical performance of the satellites (extended pass band, low-noise amplifiers, etc., included in the DSCS Ser¬ vice Life Enhancement Programme, known as SLEP). Like¬ wise, in the period

2008—2010,

commercial satellites

operating in the Ka-band are due to be purchased as part of the Wideband Gapfiller programme (WG) and the Advanced Wideband Gapfiller programme (AWG).These are expected to transmit a large fraction of unprotected military commu¬ nications. The

second main

development results

from

advances made in mass market electronics and the advent of commercial satellite constellations which may eventually call Circular orbit at 800 km, inclination 74° followed by a single satellite Circular orbit at 1400 km, inclination 82,6° followed by a cluster of 6 satellites vDiverging circular orbits at 1500 km, inclination 74°, followed by ===== a cluster of 8 satellites

into question the use of specifically military satellites in these frequency bands. The quest for budgetary savings, together with the increased number of common military actions, has incited the United States to offer these new systems as a stan¬

Figure 12.8. Orbits of non-geostationary Kosmos satellites.

dard for use during allied military operations according to protocols still under study. This is also an aim of the Global

In the first place, the likelihood of major conflict has con¬

Broadcasting Service (GBS), intended to broadcast large vol¬

siderably diminished and, since the Gulf War, sources of

umes of data to all military users across the board, and possi¬

threat have been perceived in a new light. This, combined

bly right down to the soldier in the field. Such a system

with a need for shortlived actions carried out on the

remains flexible whilst providing a quite enormous capacity.

regional scale, has meant that certain military activities can

It should meet the challenge raised by digital data transmis¬

be significantly curtailed. Hence, the main core of protected

sion, expected to increase ten-fold by 2002.

military communications, once extending over a wide range

The GBS programme can be divided into three main

of different frequencies, now tends to fall within a narrow

stages. The first involved testing military broadcasting via

band of the very high frequency region of the spectrum

civilian satellites. Operations of this type were carried out in

(EHF, i.e., 20—44 GHz), more appropriate for discreet, small

1996, for example, in the context of the Bosnia Control and

scale operations.

Command Augmentation System by the Defense Informa¬

The American programme Milstar, which began in 1982,

tion Systems Agency (DISA) and the Advanced Research

today represents the state-of-the-art in this frequency band.

Project Agency (ARPA) of the US DoD. In the second stage,

Two satellites are already operational, to be joined by four

three of the US Marine’s UHF Follow-On satellites (UFO 8,

others by 2002. The completed system will form the back¬

9, and 10) were launched with GBS payloads working in the

bone of future American EHF telecommunications. This

K-band. Finally, in the third stage, planned for 2006, the GBS

satellite system will also be equipped to operate in the lowest

system should be associated with future American military

frequency bands and should provide worldwide coverage,

satellites of the AWG type and a corresponding network of

whilst using only narrow beams to facilitate discreet recep¬

ground-based installations.

tion via portable devices weighing less than ten kilograms.

The GBS programme testifies to a changing awareness on

The US Department of Defense is already experimenting

the part of American military leaders during the period

with high speed links (1.544 Mb/s) in the frequency band

1994—1995.They felt the time had come to end the techno¬

20—30 GHz, using portable antennas measuring between

logical and budgetary excesses of great telecommunications

0.25 and 1.25 metres in diameter. This is part of NASA’s ACTS

programmes along the lines of Milstar. The new programme

programme (Advanced Communication Technology Satel¬

has been imposed upon the space telecommunications archi¬

lite). The so-called Advanced EHF satellite programme is at

tecture conceived by the US Air Force as part of a new desire

present under study as a continuation for the Milstar

to adopt a customer approach and at the same time make

programme. The gigantic costs incurred by Milstar (around

allowance for the improved performance of technologies

Telecommunications

available on the civilian market. Internal debates are not yet

j

several options remain, some motivated by purely European

over, however. At the present time, the Global Broadcasting

aspirations and some having rather more transatlantic origin,

System could only be considered as a complement to existing

none has yet been given the final go ahead. Given the exceed¬

or planned, exclusively military programmes.

ingly high volume transmission facilities in the general archi¬

As far as other countries are concerned, civilian satellites

tecture of military command and control systems, especially

are equipped with special transponders for provision of

when joint operations are run with the participation of sev¬

military communications, as in the French case, where the

eral countries, it seems likely that the final choice will be

Syracuse 1 and 2 systems are carried by civilian telecommuni¬

made in accordance with the way allied alliance systems

cations satellites. With the same aim in mind, an experimental

evolve, whether it be within the framework of NATO or the

EHF payload will be tested on the experimental satellite Sten-

gestating European Security and Defence Initiative (ESDI).

tor. The United Kingdom is an exception to this rule, having

In the meantime, programmes are pursued on a national

deployed the Skynet system very early on, with satellites simi¬

or bilateral basis. The first purely military French satellite,

lar to the NATO series. In 1997, attempts were made to organ¬

Syracuse 3, is due for launch in 2006 and an interim satellite,

ise European cooperation in the area of military space

Gapfiller, is under study. The United Kingdom is developing

telecommunications, but the scheme failed when Great

its national programme with Skynet 5 and Germany is study¬

Britain withdrew from the project in August 1998. Although

ing a national satellite known as Dmilsatcom.

Space: the new battlefield?

States possessing the kind of system just described, with a

gic space-based systems, thus preserving what is now called

military vocation, present them as an essential element in

information dominance. The second point is the ability to

their national security. Telecommunications and navigation

control access to space and its uses, if the need arises. This is

satellites (see chapter 11), together with reconnaissance sys¬

the first step towards what might genuinely be referred to as

tems, play a crucial supporting role in military actions. Cur¬

space weapons, which aim to disable enemy means either

rent thinking, especially with regard to the organisation of

temporarily or permanently.

forces, tends to treat space as an ever more decisive factor in

This last idea is not a new one. It has reappeared regularly

battle management. The American authorities openly admit

since the inception of space travel. At the beginning of the

as much: without spaceborne capabilities, the world’s most

1960s, for example, the US Air Force was an enthusiastic pro¬

powerful country would have no advantage whatsoever

ponent of orbiting assault weapons and other spaceborne

in any large-scale conventional conflict. Naturally, any

arms programmes, claiming that space, like the oceans, would

sufficiendy advanced country with knowhow in the area of

soon become the arena of conflict between the great powers.

space technology (e.g., launch, tracking, detection) may be

The advent of the atomic age made such developments irrele¬

tempted to attack enemy satellites in the hope of consider¬

vant and these ideas were regularly rejected by successive

ably weakening its opponent. Moreover, satellites are vulner¬

political authorities. The first known studies concerning

able. They have exactly predictable orbits, apart from the rare

spaceborne interception systems, or even assault weapons,

case of manoeuvrable satellites, on-board subsystems are

date from the end of the 1950s. Very little has ever come of

fragile, and it is not always possible to arrange for reserve

them, however, for both technical and political reasons.

capabilities. Finally, ground links constitute another weak

On the American side, the first half of the 1960s was

point, especially those transmitting commands up to the

marked by a few antisatellite missile tests, but the technical

satellite. It is no surprise, therefore, that the surveillance

knowhow available was insufficient to produce anything very

(fig. 12.9) and protection of military space-based systems

effective. For example, the fixed bases for the Zeus and Nike-

has today become a strategic priority.

X missiles used at the time meant that they could only target

In the United States, the term space control is used to

satellites when they passed at low altitude through a field of

invoke the new idea of maintaining an American advantage

action determined by the location of these ground bases.

in space. Two main lines would appear to be favoured. The

Worse still, they proceeded by triggering a nuclear explo¬

first is better protection for both civilian and military, strate¬

sion, which did not allow a selective action, so that not only

353

354

Military applications of space

the target but its whole environment was also affected. As a

can rendezvous tests between Gemini and Agena spacecraft,

result, tests carried out by the US Army on the Kwajalein atoll

carried out in 1966, showed that the United States was in

in the Marshall Islands were discontinued in 1968.The corre¬

possession of precisely the same capability as the Soviets.

sponding US Air Force tests carried out on Johnston Island in

These tests, carried out by NASA, were supported by the US

Polynesia using Thor missiles were finally brought to an end

Department of Defense which, a few years previously,

in 1975. Such systems should be considered as a spaceborne

had studied the Satellite Inspector Technique programme.

antibomb defense rather than an antisatellite system.

This project, whose first tests with an Agena target did not

In fact, the possibility of launching a nuclear warhead in

take place as planned in 1962, proved to be unrealistic, since

such a way that it would follow part of an orbit was never

an inspection satellite would have been required for each

completely abandoned at the beginning of the space age.

Soviet satellite.

Soviet tests referred to as Fractional Orbit Bombardment Sys¬

During this period, it seems that the United States had no

tem (FOBS) seem to have been carried out between 1966

desire to develop an ASAT system that would appear too

and 1971. The technical characteristics of a launch from

threatening, since this would have encouraged the Soviets to

space would even seem to offer a tactical advantage. It is

develop similar capabilities. The Americans no doubt had a

much easier to attain orbits in the same direction as the

greater dependence on spaceborne military systems and

Earth’s rotation, so that the United States would have been

those in charge may well have preferred to maintain as far

attacked from the Pacific, thus circumventing their most

as possible the idea of space as a haven. Moreover, Soviet

sophisticated means of defense. The shortcomings of the sys¬

means of interception only threatened low-orbiting satel¬

tem, lack of operational flexibility, inaccuracy and control

lites, and for these a certain number of countermeasures

problems, proved too great and eventually led to its aban¬

were available.

donment. The new ballistic missiles were largely superior.

A new tactical approach was adopted by the Soviet Union

Since the beginnings of space conquest, antisatellite

in 1976, after tests had been discontinued for a period of

weapons have always been at the forefront, with a particular

four years. They developed an intercepting satellite capable of

desire in the Soviet Union to neutralise reconnaissance satel¬

much greater manoeuvrability, since it could travel around

lites. The development of antisatellite satellites was therefore

different orbits before settling itself on that of the target

favoured. Known today as Poliot, these were first tested in

satellite (fig. 12.10).This ability to change from one orbit to

1963 and 1964.

another was aimed at complicating the opponent’s task. It

Tests carried out between 1968 and 1971 proved Soviet capacity to approach, and if need be, destroy a satellite, by

became impossible to determine exactly which satellite was at risk, and hence to plan protection for it.

exploding a shrapnel bomb nearby. However, the technology

The American response to this type of threat was the

required for such missions can also be tested in a more dis¬

Miniature Homing Vehicle (MHV), an antisatellite weapon in

creet manner during rendezvous missions, and these are

two stages, fired from an aeroplane. This was given the go

commonplace as part of manned space programmes. Ameri¬

ahead by President Ford in 197 7. The main interest of such a

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