Synthetic aperture radar in a near-zero inclination almost circular geosynchronous orbit: mission analysis and orbit maintenance

The Geostationary Synthetic Aperture Radar (GEOSAR) concept, first proposed in 1978, aims at defining an Earth Observation system able to provide regional coverage with large swaths, subcontinental access with very short revisit time, and quasi-persistent monitoring capabilities, by exploiting the unique characteristics of the GEO orbit. These peculiar characteristics make GEOSAR suitable to perform imaging and interferometry intended for the observation of fast-evolving large-scale phenomena, such as ground motion in natural and urban environments. However, stable acquisition configurations that such applications require, are affected, even on the short-time scale, by the GEO perturbing forces. Therefore, a specific control strategy must be implemented to ensure small cross-track baselines and maximum Doppler bandwidth overlap between subsequent acquisitions. The paper proposes a novel orbit maintenance strategy tailored for GEOSAR. It assesses the near-zero inclination GEOSAR feasibility considering interferometric requirements and International Telecommunication Union (ITU) regulations compliance, demonstrating that the overall delta-V budget of the mission remains similar to that of standard GEO satellites.