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digital elevation data and terrain contours can be compiled.
Advanced versions of each of these systems are under
development and will undoubtedly provide higher image quality
in the near future. International commercial arrangements have
been established which now make it possible to order satellite
images from any of these spacecraft for any place on Earth, and
obtain the data within a reasonable time. Numerous companies
will provide value-added processing at competitive prices.
IMAGING RADAR SATELLITES
Radar images have been acquired by the Shuttle Imaging Radar
(SIR-A,-B, and-C), but these are experimental only and obtained
from short life missions over limited areas. The Russian ALMAZ
radar satellite, which provided 15-30 m resolution data over a 60
km swath, is no longer functioning. Operational radar images are
being produced by the European Space Agency ERS-1, the
Japanese JERS-1, and most recently, by the Canadian RadarSat.
Data characteristics for these radar systems are given in Table 3.
Table 3. DATA FROM RADAR SATELLITES
System SIR-C JERS-1 ERS-1 RadarSat
country USA Japan ESA Canada
wavelength L,C,X L C C
resolution 30m 18 m 25m 10-100 m
swath 40km 75km 100 km 50-500 km
look angle variable 35 deg 23 deg 20-50 deg
cycle X 44 days 35 days 24 days
As with the electro-optical satellites, data from these spacecraft
can be purchased from commercial sources. NASA is planning
a third mission of SIR-C which will carry a second antenna
mounted on an extendable boom, so that interferometric data can
be obtained to produce terrain elevation data as well as images.
Funds have been requested for a study of a free flying radar
satellite with multiband and interferometric capability. Classified
radar satellites are reported to have a ground resolution of 1-2
meters, but these date are not available to civil mapping agencies.
RUSSIAN HIGH RESOLUTION PHOTOGRAPHY
In 1988, the USSR released photography from their
reconnaissance satellites. In these systems original film is
returned to Earth by parachute, and subsequently digitized by
scanning. Both hard copy and digital data are offered for sale
through several outlets. Characteristics of these photographic
systems are given in Table 4.
Table 4. RUSSIAN SPACE CAMERA PARAMETERS
System — MK4ÁA KFA-1000 TK-350 KVR-1000
Type Multispect Multispect Topographic Hi-Res
Cameras 4 2 1 1
EL 300mm 1000mm 350mm 1000mm
Format 18x18cm 30x30cm 30x45cm 18x72cm
Scale 1:650,000 1:270,000 1:660,000 1:220,000
Res. 6 meters 5-7 meters 10 meters 2 meters
Another camera, designated KFA-3000, with 3000mm focal
length, 18x18cm format, providing 2 meter resolution, has been
mentioned, but apparently data from this camera are not being
Sold. In general, pictures over the former Soviet Union, and allied
communist government countries, are not made available.
Comparison of the data currently available from commercial
sources, as listed in Tables 2,3,and 4, with the capabilities of the
early CORONA and ZENIT reconnaissance satellites given in
Table 1 shows the remarkable progress that has been made by
civil agencies in getting access to high quality image data for
mapping and resource evaluation.
COMMERCIAL HIGH RESOLUTION IMAGING
SATELLITES
It should be noted that all of the imaging satellites described
above have been designed, funded, built, and operated by
government organizations, and that it is only a recent
development that makes the imagery available through
commercial enterprise. But now a new approach is being
implemented. After many years of wrangling between the civil
federal government agencies, the Department of Defense, the
Intelligence Community, the users, and representatives of
commercial enterprise, the U.S. government finally approved a
set of guidelines under which commercial organizations would
be allowed to exploit formerly classified technology and build
high resolution imaging satellites, and sell the data as a
commercial venture. Several organizations have received
licenses to proceed with the construction of high resolution
panchromatic and multispectral imaging satellites for launch
within the next few years. Among these are:
Space Imaging Inc. is a consortium funded by Lockheed-
Martin, E-Systems, and Mitsubishi. Their spacecraft is
called Commercial Remote Sensing Satellite (CRSS).
The camera system is being built by Kodak. Lockheed
and Kodak were major participants in the CORONA
system development, and E-Systems is a principal
supplier of sophisticated ground processing systems to
the Defense-Intelligence community. Space Imaging is
planning a two satellite system with first launch in
1997. There will be three ground receiving stations in
Denver, Alaska, and Atlanta. In addition they are
negotiating with Regional Affiliates in several countries.
Space Imaging will supply the receiving and processing
equipment to each affiliate, who will then have
marketing rights within the sphere of their reception
station. Space Imaging will develop a world-wide data
base. An extremely agile spacecraft will permit a variety
of imaging patterns and very short revisit times.
Orbital Imaging Corporation (Orbimage) is a wholly owned
subsidiary of Orbital Sciences Corporation (OSC).
Their spacecraft called OrbView will be launched in
late 1997 by the OSC Pegasus vehicle. Controlled by
ORBIMAGES existing Center near Dulles, Virginia, the
satellite will downlink real-time imagery to receiving
and processing stations in the U.S. and other countries
with whom the company is presently negotiating. OSC
is acquiring MacDonald Detwiler and Associates, a
Canadian firm with extensive experience in ground
processing of satellite imagery. The highly
maneuverable spacecraft will be able to acquire a variety
of imaging patterns. À second generation spacecraft
with increased capabilities is already in design.
EarthWatch, Inc. is a combination of Ball Aerospace,
Worldview, Inc. and several other participants. They
are planning two cooperative spacecraft, EarlyBird to be
launched in August 1996 and QuickBird to be launched
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
