Precision radar surveillance and mapping with Discoverer II

Abstract

An affordable space-based radar system for surveillance and precision geolocation support to military forces will be developed and demonstrated in the Discoverer II program. Approaches for meeting the system performance goals within cost constraints in high range resolution ground moving target indication (HRR-GMTI), agile antenna beam pointing, and high resolution digital terrain elevation data (DTED) at Levels 3 to 5 are presented. Moving target detection performance is obtained by increased bandwidth, increased integration time, and space-time adaptive processing (STAP). An active electronically scanned array antenna with moderate field-of-view plus mechanical steering for large excursions can provide the beam agility needed for desired performance within cost constraints. Stereo SAR or interferometric SAR (IFSAR) processing can produce a high degree of DTED accuracy, if geometric collection conditions are met and the image pair is mutually coherent. Three types of orbital configurations, and combinations thereof, have been examined for their suitability for single-pass IFSAR paired orbits. Four possible collection strategies for the DTED mode are reviewed in the context of accuracy, coherence between collections, access opportunities, approximate coverage rates, and precise orbit determination. Baseline determination is an added IFSAR challenge that can be addressed with precision differential GPS or ground control points.