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Instrument: SIR-C : Spaceborne Imaging Radar-C
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The Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar
(SIR-C/X-SAR) was flown as part of the Space Radar Laboratory-1
payload launched on the Space Shuttle STS-59 on April 9, 1994.
The objectives of the Spaceborne Imaging Radar-C (SIR-C) instrument were
to investigate characteristics of the Earth's surface such as (1)
vegetation extent and biomass condition, (2) soil moisture and snow
properties, (3) recent climate change and tectonic activity, and (4)
ocean wave spectra. The SIR-C was jointly operated from the Space
Shuttle with the X-band Synthetic Aperture Radar (X-SAR), provided by the
German Space Agency (DARA)/German Aerospace Research Establishment
(DLR) and the Italian Space Agency (ASI), on the same Space Radar Laboratory
(SRL) platform. The SIR-C radar operated at L-band (24-cm wavelength or
1250 MHz) and C-band (5.6-cm wavelength or 5300 MHz) in multiple polarization
modes (HH,HV,VH,VV). The antenna was composed of two planar arrays, one for
L-band and one for C-band, in dual-polarized operation. Each array was
composed of a uniform grid of dual-polarized microstrip antenna radiators.
The SIR-C antenna was 12.2 meters, weighed over 10,500 kg and filled the
Shuttle cargo bay. SIR-C provided images of the magnitudes of HH,VV,and
cross-polarized returns, images of the relative phase difference between
multiple polarization returns, and derivation of linear, circular, or
elliptical polarization. Image resolution was 25 m (20 MHz bandwidth) and
40 m (10 MHz bandwidth). The swath width ranged from 15 to 65 km for
calibrated images and 40 to 90 km for mapping mode (SCANSAR) images.
In SCANSAR mode, the antenna was steered electronically or mechanically to
acquire data at various incidence angles (15 to 55 degrees) increasing the
swath width at reduced resolution. Data was acquired at 8 bits per sample or
4 bits per sample in 16 primary modes. SIR-C used four solid state receivers,
two each for C-band and L-band. The SIR-C data was recorded on-board on the
Shuttle Payload High Rate Recorder. The SIR program is an extension of the
Seasat SAR, SIR-A, and SIR-B instruments.
X-SAR operated at X-band (3.1-cm wavelength or 9600 MHz) with VV
polarization. The X-SAR used a passive slotted-waveguide antenna (12
meters) which was tilted mechanically to align the X-band beam with
the SIR-C C-band and L-band beams. The swath width was from 10 to 45
km at 25-km resolution with illumination angle of 15 to 60 degrees
off-nadir. The X-SAR antenna had a fixed beamwidth of 5.8 degrees in
elevation and 0.13 degrees in azimuth as opposed to the phased array,
multi-polarization antenna of SIR-C. X-SAR data was recorded on-board
on the Shuttle Payload High Rate Recorder and transmitted in real-time
(Ku-band via TDRSS) over selected regions. The X-SAR is a follow-on
the Germany's Microwave Remote Sensing Experiment (MRSE), flown on the
first Shuttle Spacelab mission in 1983. The SRL is expected to fly
again in 1994 and 1995.
The SIR-C/X-SAR Science Team was made up of 49 members and 3
associates from 13 countries. Data was collected and focused on
selected supersites in conjunction with aircraft and ground-based
observations. See Jordan,R.L., B.L.Huneycutt, and M.Werner, &The
SIR-C/X-SAR Synthetic Aperture Radar System&, Vol.79, No.6, June
There were more than 400 sites on Earth where data was taken during
the mission. Nineteen sites were designated &supersites&, making them
the highest priority targets and the focal point for the scientific
investigations. The following were the supersites targeted:
Ecology - Manaus, Brazil; Raco, Mich.; Duke Forest, NC; Central Europe
Hydrology - Chickasha, OK; Otztal, Austria; Bebedouro, Brazil;
Montespertoli, Italy
Oceanography - Gulf Stream (mid-Atlantic); Northeast Atlantic Ocean;
Southern Ocean
Geology - Galapagos Islands; Sahara Desert; Death Valley, CA; Andes
Mountains, Chile; Mount Pinatubo
Calibration - Flevoland, The Netherlands; Kerang, Australia;
Oberpfaffenhofen, Germany; Western Pacific Ocean
Rain Experiments - Western Pacific Ocean

Dr. Diane Evans (JPL) - U.S. Project Scientist
Dr. Herwig Ottl (DLR) - German Project Scientist
Prof. Mario Calamia (Univ. Florence) - Italian Project Scientist
Dr. Miriam Baltuck (NASA HQ) - Program Scientist
Michael Sander (JPL) Project Manager
Richard Monson (MtPE) Program Manager
Jim McGuire (NASA HQ) SRL Program Manager
Dr. Manfred Wahl (DARA) X-SAR Project Manager
Dr. Paolo Ammendola (ASI) Deputy Project Manager

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Instrument Owner: NASA