Spatio-temporal baseline and spatial coverage of lunar-based SAR repeat-track interferometry in single- and double-antenna configurations

Spatio-temporal baseline and effective spatial coverage are key parameters for lunar-based synthetic aperture radar repeat-track interferometry (LB-SAR RTI). In the mode of lunar-based single-antenna SAR RTI (LB-SASAR RTI) Earth observation, the temporal baseline and effective spatial coverage are affected by perpendicular baseline, which depends mainly on the lunar revolution. However, the moon is a nature celestial body; multiple SAR antennas can be installed on its surface to increase the potential in Earth observation. In this study, we first designed the observation geometry of lunar-based double-antenna SAR RTI (LB-DASAR RTI) and calculate its spatio-temporal baselines and effective spatial coverage. Comparing with those of the single-antenna mode, the results show that: 1) the perpendicular baselines of LB-DASAR RTI are 0-3000 km shorter than those of LB-SASAR RTI during a year, and approximate 98% of them are between 2000 and 3000 km; 2) the amount of interferometric combinations increase by about 23.5%; 3) the amount of interferometric combinations with large swath width (4400 km) is approximately doubled, resulting in an increase of 12.3% in the percentage of large swath width (4400 km); 4) the observation duration in azimuth is increased by at least 2-3 hours, equivalent to 30 degrees to 45 degrees of azimuthal observation range; and 5) the repeated observation frequency is higher, the most significant increase of interferometric combinations is at 40 degrees north and south latitudes, reaching up to 286 times a year. The study is helpful for the observation mode design of LB-SAR RTI and the implementation of observation data acquisition plan.