Cartwheel

Abstract

Radar interferometry gained a lot of interest in very few years in the 1990s. Its main product: the interferogram, is a map of the difference of the phases of two radar images acquired on the same site with a time elapsed between the takes that can range from zero to several years. The phase maps are ambiguous, like contour lines that would not carry any number. They need to be "unwrapped" (i.e. assigned a number) which is generally done by continuity. Several SAR system concepts have been dedicated to interferometry. The Cartwheel concept aims at maximizing the interferometric return of a conventional satellite by adding a cheap constellation of receive-only micro-satellites in a special, and very efficient, orbital configuration, which disturbs the least, or not at all, the Transmitter. Here we describe the system from its design to some specificities of the processing of the products, some of them offering unique new capabilities. Finally, we suggest some more advanced uses of the design.