Radarsat sar antenna in-flight pattern measurements

摘要

The Canadian Radarsat satellite was launched on November 4, 1995 and is now in routine operation. Radarsat's payload consists of a Synthetic Aperture Radar (SAR) imaging instrstrument, and it is the first operational satellite SAR with an antenna which can reconfigure its elevation beam electronically. The SAR Antenna is a large deployable slotted waveguide planar array (1.5m by 15m) operating at 5.3 GHz. The antenna comprises 32 slotted waveguide rows with electronic Variable Phase Shifters which are set to produce various pseudo-trapezoidal elevation beam shapes. These beams vary in elevation width from 1.6° to 11.3° and scan over elevation angles from −21° (min. near edge) to +20° (max. far edge) relative to the antenna boresight. This provides ground coverage anywhere within an accessibility strip of width greater than 500 km. The along track (azimuth plane) radiation pattern is a pencil beam. In order to achieve optimum performance, accurate beam pattern information must be used in the processing. Unlike preceding satellite SAR systems, Radarsat operates with many different beams, and so the beam characterisation is a major task. This paper describes the procedures that were used to predict the patterns before launch and to measure them in-flight, and presents results demonstrating good correspondence between the two sets of data.