PASSAT: Passive Bi Static SAR Constellation Progress and Trial Results

Persistent monitoring of large areas using spaceborne Synthetic Aperture Radar (SAR) is a challenging problem for various defence and civil applications. The PASSAT project was proposed and undertaken by the University of Birmingham, under the sponsorship of the UK Defence Science and Technology Laboratory, to analyse the concept of a fully passive (receive only) spaceborne SAR system based on a constellation of CubeSats. By making use of terrestrial transmitters (e.g. Digital Video Broadcasting – Terrestrial (DVB-T) or similar transmitters of opportunity), the problem of having to carry a high power pulsed radar transmitter on the satellite is eliminated. Instead, the satellite only need carry a suitable receiver, antenna and signal storage facility. It is expected that such a system would provide imaging of populated areas with a potential resolution of ~2-3 m. In this paper, we describe progress towards the design of such a system, including the results of a series of ground-based and airborne trials which make use of DVB-T transmissions from the Sutton Coldfield transmitter. In the processed images, roads, wind turbines, electricity pylons, hedgerows and trees are all clearly identified.