Programme aspects for future multifrequency/multipolarization SAR

In order to fulfill the user requirements in terms of different operational modes (e.g. scan and spotlight) with different parameters (e.g. look angle, resolution, swath width, polarization), a new generation X-band SAR (to be understood as part of a multifrequency SAR facility) is needed, based on an active phased array radar antenna which allows electronic beam steering and beam shaping. GaAs MMICs (Monolithic Microwave Integrated Circuits) have been identified as the critical technology for T/R-modules of active phased arrays. The wealth of polarimetric/multifrequency data collected by the two Radarlab missions and its evaluation proved without doubt the superiority of multifrequency SAR systems in comparison to single frequency ones. Therefore, future SAR missions should operate at least at two frequencies (e.g. X-band and L-band). The upper frequency is sensitive to short vegetation, crops, leaves twigs etc., the lower frequency covers biomass, soil moisture and in general penetration aspects. The mission scenario must allow a revisit time of about one week. This implies electronic beam steering must cover a wide ground swath for data take opportunities. The German Longterm SAR Programme is aimed at the development and operation of a two- or three-frequency (C,X or L,C,X)/multipolarization SAR system in the framework of a broad international cooperation. This system should be flown between AD 2003 and AD 2005 on a polar orbiting platform