Radar Satellite Constellations:

We discuss the use of radar satellite constellations, or clusters, for wide-area, high-resolution SAR. These systems are composed of multiple, formation-flying satellites with each satellite having its own, coherent receiver. Increased swathwidth compared to that of traditional SAR is attained by processing the data obtained from multiple satellites. The multi-channel system can also be scanned both forward and backward. The size and orientation of a such a system’s resolution cell can change dramatically, however, depending on the number of satellites in the constellation, the size of the constellation, the look geometry, and the subset of data that are coherently processed. In addition, any of these parameters can be varied on demand according to mission requirements. The constellation itself forms an array that is sparsely populated and irregularly spaced. Furthermore, if the constellation is of extremely wide extent, then the width of its array pattern determines resolution rather than system bandwidth and coherent integration length. Forwardand backward-looking scenarios further exacerbate the problem of predicting system resolution. In order to aid in the design, analysis, and signal processing of radar satellite constellations, we present a method of characterizing the resolution of such systems. We derive two eigensensors that can be interpreted as the dimensions of a two-dimensional synthetic aperture. Then, the synthetic aperture expression is used to derive resolution, and simulations are presented to verify the theory. Next, we use results from the synthetic aperture analysis to develop design constraints for this type of radar system. Finally, we use the analysis to suggest areas of future research.