Design of a shuttle-borne SAR for the DFVLR's planning study

A design for an X-band synthetic aperture radar (SAR) antenna to be fitted on the Shuttle Imaging Radar (SIR) antenna for measurement in X, L and C bands is proposed. The simultaneous observation of the areas to be measured allows investigation of the spectral reflectivity of different objects in the microwave range. Each radar is equipped with 12 m long planar antenna arrays mounted on a support structure rotatable in elevation giving a wide range of variability with respect to frequency, polarization and incidence angle on ground (15 to 60 deg adjustable in steps of 1 deg). The X-band SAR provides 30 m geometrical resolution and a swath of 30 to 50 km at a nominal orbit attitude of 250 km. These constraints mainly result from the data rate (maximum 46 Mbps) transmittable by the orbiter. The analog video signals are 10 bit quantized with 20 dB dynamic range and an adjustable bias (0 to 12 dB).