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English Pages 440 Year 2003
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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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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1996
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Figure 9.13. The spectral bands used by the main imaging sensors launched and planned in 2002.
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Russia Ukraine Europe Canada China China-Brazil 1 India Japan
Sensors
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1998
SPOT 4-5
AVHRR-3
1998
NOAA 15-L-M
ETM+
1999
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1999
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1999
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1999
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1999
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1999
CBERS 1, 2
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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
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accentuation of general contrast
scale
1
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mosaic
accentuation of local contrasts
geometric
analysis
classification gradient extraction
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1 r
1 r
ir
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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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Civil communications Maritime communications and navigation Experimental
□ o
a
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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(1 active, 2 inactive satellite)
O © O O O
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1990
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$Satcom-C3 Galaxy 5 ®
1991
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Solidaridad 1 (Mex)
Express 3A®
Orion 2 (Telstar 12) *
-.Galaxy 3R £i
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1992
Sirius 2
O GE 5 VIII05 • ® Brasilsat B3 QHGS 1 Q GE 3 EchoStar 3 O g PAS 6 QGE-2 0 PAS 5 III-F4 Nahuel 1A (Arg)
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1993
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Nilesat 102 (Egypt)
PAS 6B © .. ofi — VIII 06 •
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OApstar 2R Indostar A (Indon) Q QThaicom 3 (Thailand) BSat 1A ©
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Arabsat 2B 0Turksat 1C ■Arabsa ^ G32(44)*
Italsat 2
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2© Measat (Malaysia)
60
C1
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longer in activity at the beginning of the year 2001. Gorizont satellites are given theirtraditional numbering.
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1994
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1993
Superbird A1 © Optus-BlO ■ Superbird B1
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1990
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1989
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1985
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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
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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°
0°
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'
. Kourou Galapagos
•
Colombo i
Manila
0 Guam
Libreville 0 Ascension
0
St Helena Wallis 30°
Arequipa 1
# Papeete
0
Rapa
0
■
Cibinong
' Cachoeira Paulista
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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