Attitude reference generation for spacecraft with rotating solar arrays and pointing constraints

Abstract

Advancements in space technology are enabling more sophisticated spacecraft designs with time-varying spacecraft configurations to account for varying power considerations. For example, articulating solar arrays that rotate about an axis fixed with respect to the hub can track the Sun at all times. Electric thrusters also have become omnipresent in modern spacecraft designs. Because these thrusters operate over long time windows, and the thrust vector must at all times be aligned with a specific inertial orientation, the optimal spacecraft attitude reference needs to accommodate the thruster too. Multiple pointing constraints pose a challenge to the attitude reference generation problem, because the attitude is characterized by three degrees of freedom, whereas the different constraints are often described by overdetermined systems of multiple equations. This paper leverages a range of attitude parameterizations to provide a mathematical description of the solution spaces of the constraints outlined above. When the intersection space is nonzero, it is possible to compute a solution that satisfies multiple constraints simultaneously. Conversely, an ordered list of pointing priorities is required in order to enforce the most important requirements, and reformulate the subsequent ones in terms of constrained optimization problems. The attitude guidance formulation is written in a general manner, which makes it applicable to a broad range of mission configurations.