Adapting operations of the Radarsat SAR to enhance ship monitoring

The Radarsat synthetic aperture radar (SAR) instrument was designed to be very versatile in its capabilities, and the standard operations of the Radarsat SAR use only a subset of the potential imaging modes. The standard mode best suited to ship monitoring provides coverage of a swath of over 500 km, but large scale ship surveillance at mid-latitudes is limited in this mode by two factors. the interval between repeat coverage and the steep incidence angle. Ideally, the system would allow any critical area to be imaged once each day, and at higher incidence angles, where ship-to-clutter ratio is better. This paper considers alternative modes of operation for the Radarsat SAR which provide enhanced ship monitoring. These modes operate with wider beams and use significantly lower pulse repetition frequencies (PRF) and longer receive windows than the standard SAR modes. The proposed form of ship surveillance mode can be demonstrated with the system currently in orbit using the existing command data and downlink format, but with modified processing. It can provide coverage of a total swath of around 1000 km at incidence angles of 40 degrees and above. Some modest modifications which might be incorporated into a future SAR system are also suggested to enhance these capabilities further.