The interferometric cartwheel: a constellation of passive satellites to produce radar images to be coherently combined
The coherent combination of several radar images can both improve their resolution and provide accurate geometric information through the technique of radar interferometry. In this paper, we propose a constellation of passive receivers placed around a special elliptical orbit configuration, the interferometric cartwheel, which could fully exploit radar capabilities by using an existing radar satellite as the transmitting source. This orbital configuration ensures a constant interferometric baseline during the entire orbit. The proposed constellation is economical because it is passive. It can be totally independent of the source. For each type of coherent combination, we first review the principle of the measurement, using simple modelling. The principles are adapted for a passive receiver. We introduce the notion of interferometric area to select the orbital configurations. The data processing and management required for the receivers are described. We conclude with examples of constellations and their applications. We show, in particular, that the interferometric cartwheel can easily be used jointly for civilian and defence applications.