Modified phase history model for high resolution spaceborne bistatic SAR

Recently bistatic synthetic aperture radar (SAR), especially spaceborne SARs, has attracted the attention of many radar researchers. Generally, the orbit of satellite for remote sensing purposes is an ellipse with small eccentricity, and the earth should be modeled as an ellipsoid. It is well known that a second-order relative motion model can be a good approximation to a monostotic spaceborne SAR. However, for bistatic cases, this phase history model mismatches the real relative motion between a satellite and a rotating earth, dissatisfying the imaging accuracy requirement, and it limits the available azimuth resolution. In order to use the well studied SAR imaging algorithms, we develop a new second-order phase history model for bistatic spaceborne SAR using the phase error fitting method based on the ephemeris data. The new model strengthens the applicability of the conventional second-order phase history model of spaceborne bistatic SAR significantly.