First results from SIR-C calibration

The SIR-C/X-SAR imaging radar took its first flight on the Space Shuttle Endeavour in April 1994. This multi-frequency radar has fully polarimetric capability- at L- and C-band, and a single polarization at X-band (X-SAR). Calibration of polarimetric L- and C-band data for all the different modes SIR-C offers is an especially complicated problem. The solution involves extensive analysis of pre-flight test data to come up with a model of the system, analysis of in-flight test data to determine the actual antenna pattern and gains of the system during operation, and analysis of data from over ten calibration sites distributed around the SIR-C/X SAR orbit track. The SIR-C mission is the first time a multi-frequency polarimetric imaging radar employing phased array antenna has been flown in space. The effort put into the calibration of SIR-C data products has been considerable and is also unique in that this is the first time anyone has attempted to calibrate a spaceborne radar of this complexity. This work was performed by the let Propulsion Laboratory, California Institute of Technology, under contract from the National Aeronautics and Space Administration.