2.0 CURRENT RESOURCE SATELLITES
2.1 Landsats -1 through -5.
Even today, Landsat Multispectral Scanner (MSS) data is
still used by geoscientists because it is the only earth
resources satellite data available. Geoscientists found that
MSS data was found to be useful for mapping topographic
patterns of large dimensions, linear alignments of drainage
and landforms. MSS spectral data, while limited in
comparison to Landsat Thematic Mapper data, can be
processed to effectively display the abundance of iron
oxide minerals often associated with mineralized areas.
MSS data was successfully processed to display
vegetation anomalies associated with nickel laterite
deposits in Indonesia, (Taranik, et. al, 1978).
Landsat Thematic Data are now routinely used by
explorationists in most of the remote, unexplored areas of
the world. Thematic Mapper data are routinely processed
to display clay, carbonate and iron oxide abundance, and
vegetation anomalies associated with mineralization.
Landsat TM data have been the data set of choice
because nine SPOT scenes are required to cover the
same area as one TM full scene (185km by 185km),
Taranik, (1990).
2.2 SPOT
SPOT data is used for geologic and mineral resources
applications in areas where there is no Landsat-TM
coverage, or where the user wishes to sharpen Landsat-
TM data by using SPOT panchromatic data. SPOT cross-
track stereo data has seen limited use by explorationists
because of the complexity of its analysis and the costs for
multiple data set acquisitions. However, SPOT
multispectral data has been found to be more useful for
mapping iron oxide abundance than TM data because of
the location of the SPOT bandpasses. SPOT-1 currently
is parked in orbit and SPOT-2 is in standby mode. SPOT-3
is acquiring data and is planned to continue operation until
1997. SPOT satellites 1 through 3 have the same sensor
configuration and the same data characteristics.
2.3 JERS-1 (FUYO-1) Payload.
JERS-1 was launched by Japan on February 11, 1992 into
a 568.5 km orbit with a local equatorial crossing time of
10:34AM. The satellite carried an optical sensor (OPS)
and an a synthetic aperture radar (SAR) sensor. Initially
the SAR antenna panels failed to deploy and there is
suspicion that when the panels did deploy they did not
correctly orient themselves to the satellite flight path.
Although the OPS experienced problems with the infrared
focal plane early in the JERS-1 mission, some SWIR data
were acquired. The SWIR bands (three in the 2.2
micrometer region of the spectrum) added a measurement
capability not provided by the Thematic Mapper on Landsat
or SPOT. The early SWIR data showed a detector
overshoot problem which causes a streaking around the
edges of bright objects. This streaking problem is most
evident in bands 5 and 6, but band 7 appears to be very
useful. The other bands, 1 through 4 appear to provide
excellent data.
The JERS-1 SAR system has produced exceptionally good
L-band imagery of most of the terrestrial land surface of
the globe. However, there are some imaging artifacts,
probably due to asymmetry in the alignment of the antenna
pattern including: azimuth ambiguity ghosting ang
electronic interference.
2.4 Indian Government Resource Satellites
In March 1988 the Indian Government launched IRS-1A
into orbit. The spacecraft carried two types of linear array
sensors. The Linear Imaging Self-Scanning sensor (LISS-
1) and LISS-IIA and LISS-IIB. The LISS-1 sensor has a
ground instantaneous field of view of 73m and a swath of
148km and the LISS-II sensors provide a 37m GIFOV
across a 145km swath. The spectral bands for the sensors
are similar to the first four bands of Landsat-TM data.
The IRS-1B satellite was launched into orbit in the spring
of 1995 and it carried three sensor systems. A
panchromatic sensor, a LISS-II! sensor and a wide-field
sensor (WiFS). The panchromatic sensor will provide 10
meter spatial resolution over a 70km swath. The LISS-III
sensor will provide 20 meter spatial resolution in three
VIS/NIR multispectral bands over a swath of 142km and 70
meter spatial resolution in one SWIR band over a swath of
148km. The WIFS will provide synoptic coverage over a
774 swath in two VIS/NIR multispectral bands for
vegetation indices. EOSAT is making IRAS satellite data
available to the public.
2.5 ERS-1 and ERS-2 Synthetic Aperture Radar System
In 1991 the European Space Agency launched the first in
its series of synthetic aperture radar (SAR) imaging
satellites, ERS-1. This satellite provides imaging SAR data
at C-Band wavelengths (5.7cm) from a vertically polarized
antenna at 28 meter spatial resolution. The swath width is
100km and the incidence angle on horizontal surfaces is 23
degrees. ERS-2 was launched in 1995 and has the same
imaging characteristics. The orbit of ERS-2 is being
adjusted in 1996 to closely follow ERS-1 thus facilitating
the acquisition of global SAR interferometric data.
2.6 Canadian Radarsat.
In 1995 the Canadian Government launched Radarsat its
first commercial venture into space satellites. Radarsat
International, the commercial operator under the program
is selling radar data to the public. The satellite was
launched into a near polar orbit at an altitude of 798 km in
November 1995. The satellite carries a Synthetic Aperture
Radar (SAR) that operates at C-band frequencies (5.3 GHz
or 5.6 cm wavelength). The SAR utilizes electronic beam
steering to image areas on the ground at 20 to 49 degree
incidence. The SAR can image areas at variable spatial
resolution with the highest resolution at 10 meters over 45
km areas with 37 to 48 degrees of incidence. This mode
will be particularly useful for geologists, because the
geometry of imaging is almost ideal for mapping of
topographically related features on the earth's surface.
However, in the synoptic SCANSAR mode with 50 meter
spatial resolution over a 300 Km swath will be valuable for
mapping structural features of large dimensions,
particularly in areas having cloud cover at high latitudes.
The standard resolution of the system is approximately 25
meters over a 100 Km wide swath with 4 looks.
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996
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