Target shadow profile retrieval from FSSR using LEO satellites as illuminators of opportunity

In this paper, we investigate the use of Low Earth Orbit satellites as the illuminators of opportunity within a forward scatter radar system to retrieve the shadow profiles of airborne targets. We provide a mathematical description of the forward scatter shadow ratio model specific to the application scenario and demonstrate how a plane wave equivalent model can be employed
to retrieve the target shadow profile through an optimisation method. Simulations are conducted for a circular orbit with targets positioned 10 km above the ground and at elevation angles of 90, 70 and 40 degrees. The optimisation method employed to
retrieve the target's shadow profile relies on a plane wave equivalent model with a fixed plane wave equivalent distance. For both the triangular and circular targets, the retrieved shadow profiles agrees with their true shapes at all tested elevation angles.
It is suggested that the fixed plane wave equivalent distance does not significantly affect the performance of the retrieval. Nevertheless, with lower elevation angles, the fixed plane wave equivalent distance does introduce an error, slightly diminishing the accuracy of the retrieval.