GLORIA: Geostationary/Low-Earth Orbiting Radar Image Acquisition System: a multi-static GEO/LEO synthetic aperture radar satellite constellation for Earth observation

In this paper, we present a novel approach to continuous remote sensing of Earth. The proposed concept "GLORIA" drastically enhances the ability of scientists to study the Earth in a manner not possible before. The proposed system is based on a constellation of few geostationary, radar transmitter satellites and several low Earth orbiting synthetic aperture radar receiver satellites. Just as the sun is the radiation source for optical remote sensing, transmitters of microwave energy in a geostationary orbit provide the energy for radar remote sensing. Advantages of such a constellation lie in (1) a much larger number of observables, due to multi-static measurements, which significantly enhances the accuracy of retrieval algorithms, 2) the distribution of failure risk is by eliminating total system failure if a single satellite stops operating, 3) simple modular system design of small satellites through separation of transmitters and receivers (reducing weight, cost and power consumption by each satellite), and 4) flexibility in operation, that is, the receivers can be configured for different modes.