Responsive Maneuver Planning for Sun-Synchronous Repeating Ground Track Orbits

This paper investigates the suitability of sun-synchronous orbits (SSOs) as an injection location for responsive maneuverable spacecraft. This work identifies a range of near circular, repeating ground track (RGT) orbits that can be easily maneuvered into from SSOs. Four orbits that are simultaneously sun-synchronous and have a RGT are found, which could deliver high frequency imagery of a target with constant lighting conditions. A method for maneuvering between RGT orbits that are targeting different regions using high-thrust impulse propulsion is also presented. This method is used to model two possible case studies for targeting regions on demand starting from an SSO injection orbit. In comparative case study with a method that used low-thrust propulsion to move between targets, it was found that the method outlined in this paper required 94% less ΔV. A case study considering urgent response times showed that RGTs covering targets could be reached in as little as 4 hours from any starting location, but this could require extremely large amounts of ΔV (upwards of 1 km/s), while any global target could be viewed within 18 hours with a maximum ΔV of 122.5 m/s.