Attitude error cancellation for strip-map SAR by controlling steering angles of the antenna platform

Attitude error is the change in the object attitude (roll, pitch and yaw) over the ideal. Attitude error of the SAR-carrying vehicle causes a translation and attitude errors of the SAR-antenna platform. Pitch and roll of the SAR-antenna move the antenna footprint in the flight path direction and transversely to flight path respectively. Yaw of SAR-antenna introduces a squint of the antenna footprint. The change in the footprint positions due to attitude error causes a degradation of the resultant SAR image. The attitude error can be canceled by controlling the steering angles of the antenna platform in azimuth and elevation directions. This paper describes in details how the angles that the antenna platform should be steered with in the azimuth and elevation directions to cancel the attitude error can be calculated, these angles are called reference angles. In the simulation study, an actual navigation data of a SAR-carrying vehicle are used to show the attitude error effect on the footprint positions for stripmap operation, then the reference azimuth and elevation angles are calculated to cancel this error. If the antenna platform tracks the reference angles with zero tracking errors, the attitude error will be ideally cancelled. So, in the simulation study also, the antenna platform tracking of the reference angles is simulated to check the effect of the tracking errors on the footprint positions. The simulation results and their related comparisons show that the proposed work effectively cancels the attitude error.