The RF PRISM satellite concept and its application to large antenna SAR satellite

RF PRISM is a new space antenna concept where an array is fed through a mesh of points on the antenna back face with RF signals transmitted (or received) by another satellite called illuminator and usually offset by 100 km on the same orbit. Basically the PRISM deviates, amplifies, and beam forms the signals passing through it and travelling between the illuminator and the Earth. Providing that the speed vector and the main Earth viewing axis have equal incidence on antenna plane the antenna deformation control or knowledge requirement is relaxed by a factor 10. Moreover there are no longer cables between the antenna panels. RF PRISM therefore enables deployment of very large antenna in space. The illuminator satellite is not constrained by the illumination function (a few Watts and a 1m2 antenna), but just by the central payload function moved away from the satellite bearing the antenna. This can be a micro-satellite. Among others applications, this concept opens up new prospects for space-borne SAR requiring a very large antenna structure either for very low frequency (P-band), or for very high altitude (high revisit), or for single pass interferometry (two antennas). Optionally it can be combined with the SAIL, which is an another concept circumventing large antenna constraints (vertical antenna with gravity stabilisation)