Performance Optimization for the RADARSAT Constellation
- Paper number
IAC-06-B1.P.1.08
- Author
Dr. Ralph Girard, Canadian Space Agency, Canada
- Year
2006
- Abstract
In 2005, the Canadian Space Agency initiated the RADARSAT Constellation project to develop a constellation of three to six synthetic aperture radars (SAR). The new satellites are scheduled to enter in operation toward the end of RADARSAT-2, for a full implementation in 2013. The mission objectives and requirements are presented in [1]. The RADARSAT Constellation is designed to improve significantly the availability of SAR data for main Canadian Government departments, the main applications areas being maritime surveillance, ecosystem monitoring and disaster management. The most demanding requirement is to cover the maritime approaches of Canada on a daily basis at a resolution of 50 meter, which translates into a need for an imaging swath of 350 km on each satellite. The RADARSAT Constellation satellites are designed primarily for wide-area surveillance in ScanSAR mode. One peculiarity of the ScanSAR mode allows using a much smaller antenna than for RADARSAT. To cover a wide area with N beams, the resolution in ScanSAR is N+1 times the resolution is strip map mode. If one tries to cover the same area with a smaller area (keeping DC power, resolution and signal to noise ratio the same) one can show that a N/N+1 factor makes the performance almost insensitive to the antenna length. Optimizing the system for ScanSar, it was found that an antenna with an area of 9.5 m2 (instead of 22.5 m2 for RADARSAT-2) could be used, resulting in an overall spacecraft mass and volume compatible with a low-cost launcher. The use of a small antenna is creating other problems though. The two main problems being a larger number of ScanSAR beams to process (up to 14 for some configurations) and steep variations of the sensitivity due to the use of focused beams and single look in azimuth. New techniques have been investigated to equalize the system performance. The techniques consist in interleaving the beams in a non-consecutive manner or varying the beam direction during a ScanSAR burst to reduce the variation in sensitivity. In addition to these techniques, beam stitching and block processing can be shown to eliminate most problems associated with beam discontinuities for the main applications to be supported. At the end, performance optimization allows to realize a small-antenna design that provides a very good performance. The paper provides details on the techniques that have been investigated and reports the predicted SAR payload performance for different applications. [1] G. Séguin, "A Canadian Constellation of C-Band SAR Satellites", IAC 2005, Fukuoka, Japan
- Abstract document