Nearly Zero Inclination Geosynchronous SAR Mission Analysis With Long Integration Time for Earth Observation

In this paper, the performance of a nearly zero inclination and low eccentricity geosynchronous synthetic aperture radar (GEOSAR) mission for midlatitude (30 $^{circ}$–60 $^{circ}$) Earth observation is analyzed. The slow motion of such satellites with respect to the Earth's surface makes it necessary to consider long coherent combination of pulses during hours to reach the desired along-track resolution. A system based on moderate transmitted powers and antenna sizes is considered. The necessary sensitivity in such GEOSAR system is obtained from the accumulated energy of the raw data using a pulse repetition frequency above the Doppler bandwidth and a long integration time. Several issues as a result of the long acquisition, such as target and atmospheric phase screen decorrelation, speckle noise impact on the received signal, and satellite station-keeping requirements, are analyzed. The feasibility of such systems to be placed on a broadcasting communication satellite makes nearly zero inclination GEOSAR a low-cost alternative of current SAR missions.