Wavelet-based despeckling for onboard image processing in a small satellite SAR maritime surveillance constellation

New developments in small spacecraft capabilities will soon enable formation-flying constellations of small satellites, capable of performing remote sensing missions at low cost. One such mission concept under investigation involves a maritime surveillance microsatellite constellation. Two or more small microsatellites will follow a large synthetic aperture radar (SAR) transmitter, each carrying a SAR receiver antenna and one carrying an automatic identification system (AIS) antenna. Voluntary broadcasts of vessel position and velocity via AIS are received and decoded, and compared with SAR observations to verify the data and identify potentially non-cooperative vessels. Limited transmit power and downlink time will dictate that data be processed onboard the spacecraft. Herein we demonstrate a wavelet-based speckle removal method from the novel perspective of the maritime surveillance microsatellite mission, comparing wavelet thresholding methods and demonstrating that the resulting filter effectively removes speckle for improved target detection, reduces the size of the imagery data, and preserves detail necessary for registration and target evaluation.