SAR satellite orbit design for visibility-optimal coverage

Presently, governments or large corporations can choose to invest in the development and operation of synthetic aperture radar (SAR) satellites to monitor a predefined set of target locations with desired observation characteristics. Historically, observation characteristics primarily pertained to the temporal sampling resolution of high-interest targets and the geometric consistency of observations. However, given the reduction in competing stakeholder interests afforded by satellite ownership, other observation characteristics can be considered in the orbit design process that further improve the quality of collected data. To this end, this work considers the presence of geometric distortions during the orbit design process. Accounting for geometric distortions is important since their presence constitutes a loss of information in the collected image. The presence of geometric distortions within a region of interest (ROI) can be reduced by controlling the relative orientation between the satellite’s viewing geometry and illuminated topography. Using recent advancements in SAR observation planning for visibility-challenging terrain, this work develops an orbit design process for low Earth orbit (LEO) repeat ground track (RGT) orbits that reduce the presence of geometric distortions. A metaheuristic optimization approach is used to optimize the right ascension of the ascending node (RAAN) over the entire range of inclination angles to maximize the average visibility of one, or multiple, targets. General trends in average visibility as a function of inclination angle are presented for a single target case. Then, key points are presented for considering multiple targets with similar and dissimilar visibility distributions. The presented results show the first explicit incorporation of ROI visibility into the SAR orbit design process and demonstrate the resulting improvement in data quality. • Developed SAR satellite orbit design framework that incorporates target visibility. • Extracted trends in orbit visibility as a function of RAAN and inclination. • Analyzed how orbit visibility changes when designing for multiple targets. • Described visibility tradeoffs present when designing for multiple targets.