InSAR Microsatellite Constellations Enabled by Formation Flying and Onboard Processing Capabilities

The advancing development of low-cost small satellite platforms is a compelling driver for future remote sensing constellation missions. Multistatic interferometric synthetic aperture radar (InSAR) is a promising payload for such missions, potentially also in combination with additional remote sensing data. Significant challenges associated with using low-cost platforms for multistatic interferometric applications include the requirement of precise knowledge of the baseline distances between the spacecraft, and the high data volume generated (in the hundreds of megabytes per image), in light of the limited downlink capability of a microsatellite platform. To address these challenges, the Space Flight Laboratory (SFL) is making progress in a number of areas. CanX-4 and CanX-5 are a pair of identical nanosatellites designed by SFL, that will demonstrate formation flight in 2012 and enable future microsatellite constellation missions with sub-centimeter inter-satellite baseline knowledge. In regard to the data volume issue, it is observed that application-specific data requirements can be significantly smaller than the total amount of imagery collected. For example, the data required by a ground moving target indication (GMTI) mission may be limited to the position and velocity of targets, rather than entire images. Real-time image processing methods currently in development at SFL will enable onboard SAR focusing, automated image registration using precise orbit knowledge and frequency domain alignment methods, and interferometric image processing, allowing the downlink data volume to be reduced according to specific application needs. This paper discusses how CanX4&5 technology together with real-time image processing approaches can be used to enable high performance sparse aperture missions on low-cost, small platforms.