OPTIMIZING SPACECRAFT ORIENTATION TO ACHIEVE MULTIPLE POINTING REQUIREMENTS

Abstract

The Otter spacecraft is a small satellite built and operated by the Naval Postgraduate School that hosts Tui, a payload built by New Zealand’s Defence Science and Technology group, which must be activated and idled many times over a three-orbit experiment cycle. This thesis investigated the possibility of orienting Otter in such a way that it would be able to maintain nadir tracking within a certain degree of error while also facing its largest solar panel array towards the sun to maximize the amount of generated solar power. First, the analysis of Otter’s power budget was conducted throughout the three-orbit experiment cycle to determine if optimization was required to increase the amount of power available. Next, the optimal control problem formulation for this problem, including dynamic functions, path constraints, and a cost function, was performed. The objective of the resulting optimized quaternion history for the three-orbit experiment cycle was to minimize the pointing error between Otter’s solar panel vector and the sun unit vector, thus maximizing solar panel power production. Through solving this problem formulation, it was found that it was possible to produce a feasible quaternion history to achieve this objective. This quaternion history only met three of the required six optimality conditions that qualify the solution as mathematically optimal; however, the attitude solution enables Otter to generate enough additional power to power Tui throughout its experiment.