Options for airborne interferometric SAR motion compensation

Airborne interferometric SAR (InSAR) has the potential to provide topographic data with a precision of the order of one meter. However, to generate data accurate to this level it is essential to measure and compensate for nonlinear motion of the two antennas which constitute the interferometric baseline. Conventional motion compensation techniques are extended to the two-channel imaging scenario of InSAR. Phase compensation of both channels to the same reference track and compensation to two separate tracks are considered and modeled using point target simulation, and real InSAR data. The single track approach allows track segmentation to follow aircraft drifts without causing discontinuities in the differential phase, but is sensitive to range cell migration effects. The dual track approach is not sensitive to these errors but suffers from discontinuous differential phase at segmentation boundaries, which complicates the phase unwrapping process. A new formulation for each approach is presented that compensates for unknown terrain coupled with low frequency aircraft motion. In addition, a new approach that uses the dual track approach initially and then converts to a single reference track after compression is proposed. This realizes the benefits of both approaches with only a small increase in computation.