An Analysis of Spatiotemporal Baseline and Effective Spatial Coverage for Lunar-Based SAR Repeat-Track Interferometry

Lunar-based synthetic aperture radar repeat-track interferometry (LB-SAR RTI) is expected to play a significant role in addressing science issues pertaining to Earth dynamics because of its large-scale, long-term, and stable Earth observation (EO) ability. The distribution of the spatiotemporal baseline and effective spatial coverage are of great importance in the observation mode design and data acquisitions plan of LB-SAR RTI. Here, we describe the observation geometry and present the calculation method of the spatiotemporal baseline and effective spatial coverage of LB-SAR RTI. Using the Jet Propulsion Laboratory DE430 ephemeris, the results show that, first, the 1, 26, and 27 repeat cycles temporal baselines have the highest number of effective interferometric combinations, accounting for 50% of the effective observations; second, the optimal temporal baselines of LB-SAR RTI for large-scale EO are 26 and 27 repeat cycles, and the effective spatial coverage could reach up to 360° × 40° (longitude × latitude) in one day; and third, LB-SAR RTI can be used to observe the Earth's surface between latitudes 80° N and 80° S with different frequencies of observation that reach a maximum at latitudes 40° N and 40° S and decrease gradually toward the polar and equator regions. The lunar-based observation plan should take into account the initial observation time, temporal baseline, and effective spatial coverage.