Noncooperative Repeat-Pass Space-Surface Bistatic InSAR: Method and Processing

Space-surface bistatic synthetic aperture radar (SS-BSAR) system consists of a spaceborne synthetic aperture radar (SAR) transmitter and ground-based receivers. This system has the advantage of multiple angles for observation, which can improve imaging capability and deformation measurement dimensions by differential interferometric SAR (D-InSAR). With the increasing number of spaceborne SARs and various corresponding working modes, processing SS-BSAR data with public ephemeris (generally inaccurate) and unknown signal parameters is significant for the full use of illuminators. This noncooperative status will result in interferometric phase errors in repeat- pass SS bistatic InSAR (SS-BInSAR), leading to deterioration of deformation retrieval accuracy. To address this, this article focuses on the method and processing of noncooperative repeat-pass SS-BInSAR. First, a repeat-pass SS-BSAR interferometric model was established. Based on this, the impacts of time synchronization errors and orbit errors on repeat-pass interferometric phase are modeled. Furthermore, an end-to-end compensation approach is proposed for accurate interferometric processing. This approach includes accurate estimation for signal parameters, interferometric phase error elimination, and digital elevation models (DEMs) fusion recovered from multiple observations. Finally, a repeat-pass SS-BInSAR experiment utilizing the Chinese Lutan-1 as the transmitter is carried out to verify our methods. The results show a centimeter-level accuracy of deformation measurement by a single InSAR pair, indicating a great potential of SS-BInSAR in deformation retrieval.