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 1991. 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 Personnel: 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 Group: Instrument_Details Entry_ID: SIR-C Group: Instrument_Identification Instrument_Category: Earth Remote Sensing Instruments Instrument_Class: Active Remote Sensing Instrument_Type: Imaging Radars Short_Name: SIR-C Long_Name: Spaceborne Imaging Radar-C End_Group Group: Associated_Platforms Short_Name: STS-59 End_Group Online_Resource: http://southport.jpl.nasa.gov/ Group: Instrument_Logistics Instrument_Owner: NASA End_Group End_Group
SIR-C
Imaging Radars