Developing Contingency Options for INCUS: Differential Drag for Constellation Maintenance

INCUS is a NASA Earth Venture Mission expected to launch in 2026. The INCUS constellation is composed of three low-thrust smallsats (Observatories) flying in formation in low Earth orbit, with the second and third Observatories are separated by approximately 30 and 120 seconds in-track from the first Observatory. In this paper, we demonstrate that differential drag is a robust backup option for the maintenance of the phasing offsets between the Observatories. Algorithms for defining high- and low-drag windows are detailed and notional maintenance maneuvers are generated. The impact of the altitude, solar flux, and spacecraft properties on the timing and duration of the differential drag maneuvers is explored in sensitivity study. An improved shape model for the Observatory is constructed to get a refined estimate of the frequency of the phasing maintenance.