Responsive Maneuver Planning for Sun-Synchronous Repeating Ground Track Orbits

Abstract

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 an 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 a 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 55% less ΔV. A case study considering urgent response times showed that RGTs covering targets could be reached in as little as 4 h from any starting location, but this could require extremely large amounts of ΔV (upward of 1 km/s), while any global target could be viewed within 18 h with a maximum ΔV of 122.5 m/s.