FORCE MODELING AND STATE PROPAGATION FOR NAVIGATION AND MANEUVER PLANNING FOR CUBESAT RENDEZVOUS, PROXIMITY OPERATIONS, AND DOCKING

The state propagation accuracy resulting from different choices of gravitational force models and orbital perturbations is investigated for a pair of CubeSats flying in formation in low Earth orbit (LEO). Accurate on-board state propagation is necessary to autonomously plan maneuvers and perform proximity operations and docking safely. The primary perturbations affecting both absolute and relative orbital dynamics in LEO are expected to be J(2) and drag. However, the effect of drag on the relative dynamics is highly dependent on differences in the ballistic coefficients of the two spacecraft, differences which can be large since the CubeSats are non-symmetric in terms of cross-sectional area for different attitudes. Propagation accuracy is investigated both in terms of the absolute (chief) state and the relative (deputy relative to chief) state. Different perturbing effects are normalized and compared on an order of magnitude basis over a wide range of altitudes and inclinations in LEO, and in detail for a 425 km Sun-synchronous orbit.