A Two-Step Phase Calibration Method for Tomographic Applications with Airborne SAR Data

Abstract

The extraction of accurate information from repeat-pass airborne multi-baseline (MB) synthetic aperture radar (SAR) data stacks requires a very careful phase calibration to compensate for residual baseline errors. Focusing on tomographic applications, in this paper we experiment a two-step phase calibration algorithm which is independent of the nature of scattering and can operate with an arbitrarily low number of images. In a first step, the baseline errors with respect to the master acquisition are estimated by means of a multisquint processing carried out for each single baseline with respect to the master acquisition. In a second step, the residual phase errors are compensated by means of a coherent optimization based on the minimization of the entropy of the tomographic profiles. The effectiveness of this two-step procedure is tested with MB airborne data sets acquired at different frequencies over forest and ice scenarios.