Bistatic SAR Imaging and Precise Orbit Determination Using Geostationary Telecommunication Satellites

SAR satellite missions from geostationary orbits (GEOSAR) would offer the short revisit times required in the observation of fast phenomena. Ground-based multiple baseline interferometry is a technique under study for precise orbit determination of GEO satellites, a requirement for SAR processing echo data in GEOSAR missions. This interferometric technique can be complementary to GNSS-based orbit determination which is degraded for high-altitude missions above the MEO GNSS constellations. A multichannel coherent receiver is presented with two complementary functions: interferometric orbit determination and bistatic SAR imaging using present GEO telecommunication satellites transmissions. To improve orbit determination, large baselines are formed based on urban reflectors of opportunity. The obtained orbits are the basis for synthetic aperture focusing of received echo data allowing to form images from the urban and natural areas surrounding the interferometer site. In return, the images allow to select new reflectors of opportunity that can be used to increase the number of baselines and further improve the orbits. The article describes the developed system, the synergies between both orbit and imaging functions and preliminary experimental results with interferometric and polarimetric applications.