Guidance and Control Assessments of Psyche Mission’s Monthly Operations Sequences

Abstract— The Psyche mission, launched in October 2023, relies on its Guidance, Navigation, and Control (GNC) subsystem for reaching and orbiting the (16) Psyche asteroid. Once there, the GNC subsystem will facilitate the mission return valuable science data on the metal-rich asteroid. The Psyche spacecraft includes multiple sensors and actuators as part of its GNC subsystem, and each component has unique operational capabilities and behaviors that, together with mission requirements, influence GNC algorithm designs. The GNC subsystem is part of the broader mission’s flight system, necessitating that its operational sequences, built approximately monthly, are reviewed by GNC and the rest of the flight subsystems. This monthly sequence review process is designed to ensure that the inputs to the sequence build from each spacecraft subsystem have been collected and implemented in a safe and effective manner. Each subsystem has a unique process for assessing the draft sequences, which are collections of relative-timed commands, and may include periods of thrusting using electric propulsion thrusters, coasting, performing science activities, performing maintenance and characterization activities, momentum management activities, and other behaviors necessary for maintaining the health of the spacecraft. This paper presents the process by which the GNC subsystem reviews the monthly sequences. It also provides an overview of the tools used to assess the sequences’ readiness for flight, including a high-fidelity simulation of the GNC commands using the Controls Analysis System Testbed/GNC Integrated Systems Testbed (CAST/GIST), the vector fit tool (VFT2), constraint checker, and Small Forces Tool. Additionally, the paper describes the individual checks that the responsible GNC engineer performs to ensure the sequenced commands meet the GNC subsystem’s flight rules and guidelines. Lastly, the paper describes the products that the GNC review process provides to the other subsystems to aid their own review processes.