Determination of the vertical pattern of the SIR-B antenna

Abstract

Determination of the antenna pattern is important for a spaceborne Synthetic Aperture Radar such as Shuttle Imaging Radar-B (SIR-B). For SI R-B the antenna was so large that apart from one section, no complete pattern could be measured on the ground. Attempts were made to measure the pattern while the shuttle was in space by using ground receivers and active radar calibrators. The method used and described here is a supplement to these measurements. The vertical pattern of an antenna can be extracted from radar signals returned from regions whose scattering coefficients versus incidence angle characteristics are suitably flat and uniform. The method used here shows that the main vertical lobe of the SIR-B antenna is slightly wider than previously reported (6·9^° at 3dB points versus 6·2^° used in radiometric corrections).