Session
Technical Session 5: Ground Systems
Location
Utah State University, Logan, UT
Abstract
This work demonstrates a high-level mission planning method for maximizing data output from a pair of scientific CubeSat missions. The proposed approach identifies the optimal sequence of attitude maneuvers to perform in order to maximize total downlinked data over the mission, while considering constraints on available power. Many scientific satellite missions consist of at least three target attitudes: pointing solar panels towards the Sun for power, pointing an antenna towards a ground station to transmit data, or pointing a payload towards a point of scientific interest. While careful mechanical design of the mission may enable all three (or more) target attitudes to be achieved simultaneously in certain cases, in general a decision must be made about which target to point to at what time in order to optimally achieve mission objectives and satisfy mission constraints. In this work, we develop a mission planning method that maximizes the volume of data downlinked to the ground over the mission time horizon while respecting constraints on battery level. The optimization problem is posed as an integer program over the space of attitude trajectories and subject to battery constraints. The solution of this problem is an attitude sequence that can be used as a reference for a low-level attitude controller to track. Previous work on this problem suffered from slow solution time for complex mission scenarios which constrained the realism of simulations performed for validation, so in this work we build on our prior approach by leveraging more advanced pruning and search methods to improve optimizer efficiency. We demonstrate the proposed approach on two CubeSats: IMPRESS and EXACT, both currently in design and sharing many mechanical specifications. Both CubeSats are controlled by low-bandwidth actuators and have three main attitude targets: the Sun for power, the Crab Nebula or the Sun the scientific mission, and ground stations for communication. Using simulated orbit data, we show the effectiveness of this method in squeezing mission performance out of both CubeSats while maintaining on-board power. Additionally, the proposed method can run faster than real-time for time horizons of several orbits, enabling a high level of autonomy in orbit.
Optimal Attitude Guidance for the EXACT and IMPRESS Cubesats using Graph Methods with Pruning
Utah State University, Logan, UT
This work demonstrates a high-level mission planning method for maximizing data output from a pair of scientific CubeSat missions. The proposed approach identifies the optimal sequence of attitude maneuvers to perform in order to maximize total downlinked data over the mission, while considering constraints on available power. Many scientific satellite missions consist of at least three target attitudes: pointing solar panels towards the Sun for power, pointing an antenna towards a ground station to transmit data, or pointing a payload towards a point of scientific interest. While careful mechanical design of the mission may enable all three (or more) target attitudes to be achieved simultaneously in certain cases, in general a decision must be made about which target to point to at what time in order to optimally achieve mission objectives and satisfy mission constraints. In this work, we develop a mission planning method that maximizes the volume of data downlinked to the ground over the mission time horizon while respecting constraints on battery level. The optimization problem is posed as an integer program over the space of attitude trajectories and subject to battery constraints. The solution of this problem is an attitude sequence that can be used as a reference for a low-level attitude controller to track. Previous work on this problem suffered from slow solution time for complex mission scenarios which constrained the realism of simulations performed for validation, so in this work we build on our prior approach by leveraging more advanced pruning and search methods to improve optimizer efficiency. We demonstrate the proposed approach on two CubeSats: IMPRESS and EXACT, both currently in design and sharing many mechanical specifications. Both CubeSats are controlled by low-bandwidth actuators and have three main attitude targets: the Sun for power, the Crab Nebula or the Sun the scientific mission, and ground stations for communication. Using simulated orbit data, we show the effectiveness of this method in squeezing mission performance out of both CubeSats while maintaining on-board power. Additionally, the proposed method can run faster than real-time for time horizons of several orbits, enabling a high level of autonomy in orbit.
