Measuring 3-D Surface Motion With Future SAR Systems Based on Reflector Antennae

Abstract

A conventional interferometric synthetic aperture radar (SAR) system provides 1-D line-of-sight motion measurements from repeat-pass observations. Two-dimensional motions may be measured by combining two observations from ascending and descending geometries. The third motion component may be retrieved by adding a third geometry and/or by integrating along-track measurements although with much reduced precision compared to the other two components. Several options exist to improve the accuracy of retrieving the third motion component, such as combining left-and right-looking observations or exploiting recently proposed innovative SAR acquisition modes (BiDiSAR and SuperSAR). These options are, however, challenging for future SAR systems based on large reflector antennae, due to lack of capability to electronic beam steering or frequent toggle between left-and right-looking modes. Therefore, in this letter, we assess and compare the realistic acquisition scenarios for a reflector-based SAR in an attempt to optimize the achievable 3-D precision. Investigating the squinted SAR geometry as one of the feasible scenarios, we show that a squint of 13.5 • will yield comparable performance to the leftlooking acquisition, while further squinting outperforms this or other feasible configurations. As an optimum configuration for 3-D retrieval, the squinted acquisition is further elaborated: the different acquisition plans considering a constellation of two satellites as well as the challenges for data processing are addressed.

Estimating Strain and Rotation From Wrapped SAR Interferograms

“…The inversion is completely analogous to the inversion of the 3D displacement vector [11] [12] [13]. Therefore all the considerations regarding the performance with diverse acquisition geometries are valid also for the inversion of Equation 3.…”

“…Currently SAR missions observe a given area on the Earth with ascending and descending geometries only. In cases where SAR footprints from different tracks strongly overlap, a third geometry is available for the inversion, nevertheless such a configuration has proved to be ill conditioned [13]. Hence left looking or squinted acquisitions have to be used in order to achieve a sufficient inversion accuracy [11] [13].…”

“…In cases where SAR footprints from different tracks strongly overlap, a third geometry is available for the inversion, nevertheless such a configuration has proved to be ill conditioned [13]. Hence left looking or squinted acquisitions have to be used in order to achieve a sufficient inversion accuracy [11] [13]. For this experiment three TerraSAR-X stripmap interferometric pairs have been acquired in ascending right-looking and descending right/left-looking (coverage is shown in Figure 2).…”

Retrieval of Three-Dimensional Surface Deformation Using an Improved Differential SAR Tomography System

“…Results of existing methods for retrieving the 3-D deformation show that the higher the diversity of the geometric configuration (the satellite heading angle and incidence angle of antenna) of the combined SAR data is, the more accurate the North-South retrieval results will be [12]. This provides an effective way to improve the accuracy of North-South deformation retrieval.…”

A Novel Imaging Algorithm for Focusing High-Resolution Spaceborne SAR Data in Squinted Sliding-Spotlight Mode

“…Moreover, since the backscattering properties of some targets are likely to vary as a function of squint angle, the squinted SAR can obtain more information for ROI with multiple images at different squint angle observations. The squinted spaceborne SAR has great potential in detecting Earth surface deformation in three dimensions [3], and can be used for earthquake damage assessment and rescue [4], etc. Therefore, the spaceborne Jie Chen, Hui Kuang, Wei Yang and Pengbo Wang are with School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China (e-mail: yangweigigi@sina.com).…”