SAR image post-processing for acquisition trajectory change

Abstract:
Locally on a SAR image, the space frequencies can be mapped to the integration time cross radar bandwidth domain (this is the principle of both frequency-domain ω-κ a.k.a. range-migration and polar formatting types of SAR synthesis algorithms). Thus a SAR image can be post-processed by locally remapping and phasing its space frequencies to refocus the image for example according to an improved trajectory or a terrain elevation change. The main limitations are the non stationarity of the correction in the generic case and the azimuth extend of the focus blur, which constrain respectively the mesh size of the correction and the azimuth window size, result in a computation cost higher that ab nihilo SAR synthesis with the new trajectory/terrain elevation model. This is illustrated with typical airborne SAR image in mountainous area acquired by ONERA airborne radar Sethi.