Clutter Impacts on Space Based Radar GMTI: A Global Perspective

Space based radar has long been considered as a solution to the Department of Defense´s requirement for persistent surveillance of the earth surface. Ignoring the logistical issues of launching, deploying, and maintaining a large phased array in space, space based radar has the advantage of being remote and has the capability to perform global surveillance in all weather conditions. In this paper effects such as earth rotation, range fold over, varied terrain types and internal clutter motion are analyzed for their impacts on space based radar performance. Publicly available data bases allow for the characterization of the entire earths surface in terms of land cover and wind. From this data site specific clutter returns can be generated in a high fidelity radar simulation which can in turn be analyzed to produce performance comparisons under various effects. More over, a new class of waveforms referred to as ´hybrid chirps´ are introduced that can be used to resolve the range fold over (ambiguous returns) impact seen by a space based radar. These ambiguous range returns, when impacted by earth rotation, can impart delirious effects to minimum discernable velocity performance. The impacts of the afore mentioned effects on minimum discernable velocity, and the benefits of transmit waveform diversity to counter these effects are presented in this paper.