DEVELOPMENT OF THE ERS-1 ACTIVE RADAR CALIBRATION UNIT

This paper describes the development of a microwave Active Radar Calibration Unit (ARC) used as a ground calibration reference standard for the European Remote Sensing Satellite ERS-1 imaging Synthetic Aperture Radar. Three such units are placed across the radar swath giving point target returns with a known signal strength and are used to calibrate the radar image. The units have been designed for maximum stability with temperature (<0.1 dB over the temperature range of - 15-degrees-C to + 35-degrees-C); for absolute calibration the ARC is referenced to a flat plate using a novel technique of multiple transmission in its self calibration mode, achieving an absolute calibration error of < 0.14 dB.