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4.18 Dutch CEASAR and MARCS
The Dutch International Institute for Aerospace Survey and
Earth Sciences (ITC) has been involved in the
development of the CCD Airborne Experimental Scanner
for Applications in Remote Sensing (CEASAR). This
instrument covers the 400 to 1100nm spectral region with
3 bands, 3-50nm bandwidth, between 535-895nm in the
"land observation mode" and 9 bands of 20-60nm
bandwidth in the 400-1100 region in the "sea observation
mode." MARCS is the Multispectral Airborne Reference-
aided Calibrated Scanner covering the 310 to 1300nm
spectral region with 8 bands in the 310-1100nm region, 2
bands in the 1600-1780nm region, 2 bands in the 2100-
2380nm region, 2 bànds in the 3400-5300nm region and 2
bands in the 9000-13000nm region. The scanner
bandpasses range from 50nm to 150nm in the VNIR/SWIR
region and 700nm to 5000nm in the TIR region. The
ground instantaneous field of view is 4.2 meters at a flying
altitutde of 500 meters.
4.19 Summary
Within the next decade a new generation of instruments
wil be developed that will have great application to mineral
resources and geologic applications. These instruments
should enable geoscientists to not only discriminate
important mineral species, but to identify the minerals
themselves. By being able to characterize mineral
assemblages in this manner, geoscientists should be able
to better describe mineral resource potential and develop
critical information for engineering and environmental
geology.
5.0 ADVANCED RADAR SYSTEMS
5.1 SIR-C/X-SAR
In April and October 1994 NASA flew the Space Radar
Laboratory on the Shuttle Endeavor in a 215 kilometer orbit
with 57 degree inclination. This $366 million radar system
was the most sophisticated system ever flown in space.
The synthetic aperture radar imaging system had three
different frequencies (L-band, C-band and X-band) and
four different polarizations which transmitted and received
data vertically or horizontally (HH, VV, HV or VH). The
System provides data in standard products at
approximately 25 meter spatial resolution, in scenes that
cover approximately 20 by 60 kilometers. The system is a
calibrated system which maintains calibration below 5dB.
During the two missions a total of 50 hours of data,
corresponding to roughly 50 million square kilometers of
ground coverage was covered on each mission. The
ground swath varied between 15 to 90 kilometers
depending on the incidence angle.
The SIR-C instrument was built by the Jet Propulsion
Laboratory of the California Institute of Technology and
consisted of the L-band and C-band antennas. The L and
C bands use distributed phased-array antennas with
electronic beam steering. The X-SAR was built by Dornier
and Alenia Spazio companies and is a single-frequency
radar which uses a passive slotted waveguide and a tilt
mechanism to point the antenna.
693
The data products consist of survey strips of data in hard
copy film form, or in CD-ROM form. Approximately 50 CD-
ROM's were produced for the survey data for each
mission. These products are four-look data for SIR-C and
eight-look data for X-SAR with 50 meter pixel spacing and
100 meter resolution. The precision product is a frame
image of a subset of the data. The precision products
have 12.5 meter pixel spacing and approximately 25 meter
resolution. The precision products are provided on 9-track,
6250 bpi tapes or on Exabyte tapes.
Preliminary analysis of SIR-C/X-SAR data has shown that
it is an exceptional data set which covers parts of most of
the continental areas of the world. After the Principal
Investigators complete their initial investigations of the
data, the data set will be transferred to the EROS Data
Center in Sioux Falls, South Dakota and that government
facility will make the data available to the general public.
While SIR-C/X-SAR was an experimental system and two
experimental flights were planned in the original mission,
the Jet Propulsion Laboratory is seeking to fly the system
again, in the winter. months and/or perhaps have the
Shuttle payload flown as a free-flyer for two to three years.
This system would provide near-global coverage within a
few months of launch. The data produced would be
outstanding for explorationists and would compliment the
commercial monospectral radars.
5.2 Interferometric Synthetic Aperture Radar (IFSAR)
An interferometric SAR uses two different antennas,
separated by 1 to 30 meters in space while looking at the
same terrain on the ground. The antennas may be
mounted on the same imaging platform or on two platforms
that have the same imaging characteristics at the time of
imaging. The amount of separation is limited by the
wavelengths utilized by the SAR. The displacement of
terrain in the images is small, but because the SAR
illumination is coherent, the phase difference in each pixel
can be measured to meter or better accuracy, (Mussio and
Light, 1995). In one year of mission operations an
interferometric SAR might be able to provide a digital
global map of terrain at 5 meter heighting accuracy in 30
ground instantaneous fields of view. Experiments with
ERS-1, JERS-1 and SIR-C/X-SAR have demonstrated
applications ranging from analysis of earthquake
displacements to pre-eruptive deformation of volcanoes.
Currently, the Jet Propulsion Laboratory is seeking to
develop this capability for the United States and Japanese
MITI and NASDA are in the pre-development phases for a
satellite system.
5.3 Japanese VSAR
The Japanese plan to fly a second spaceborne L-band
SAR which will have 20 to 50 degree incidence angle
imaging, 10 meter spatial resolution over a 70km swath
and dual polarization (HH or VV). In SCANSAR mode the
system should be able to acquire 100 meter spatial
resolution over a 250km swath (Osawa, et. al., 1995). This
mission is planned to acquire a world-wide data set within
one year of the planned launch in 1999. The Ministry of
International Trade and Industry and Japanese earth
resources industry is sponsoring the new mission.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996
