Session
Technical Poster Session III
Location
Utah State University, Logan, UT
Abstract
Small satellite image collection missions typically rely on commercial, off-the-shelf products with control systems that use established methods for managing spacecraft attitude operations. Controllers in this marketplace simply move the spacecraft between commanded orientations without considering solar exposure. In particular, performing a specified slew based on traditional methods may keep solar arrays in shadow, draining the satellite’s power. To compensate, satellite operation teams often command the vehicle to enter a “sunbathe” state between collections. This additional level of complexity requires manual or rigidly prescribed specification of the frequency and duration of the “sunbathe” operation. However, there is opportunity for power collection during movement if satellite slews are controlled to optimize solar exposure in combination with control input. This paper describes development of a novel satellite slew maneuvering controller that optimizes satellite power state. By controlling reaction wheel accelerations and orienting solar arrays during slew maneuvers, opportunities for both image collection and power collection and consumption are considered. The controller reduces the need for operator decisions by integrating power collection with imaging tasks. This approach first prioritizes several image collection targets using an image collection score and slew cost in discretized time to generate a directed acyclic graph. The optimal collection path through the graph is then computed to generate a representative slew plan for the power state optimal controller. In simulation of several scenarios, satellite behavior reflected power-prioritized objectives while achieving collection requirements. Performance of the power-optimal controller was compared with a standard small satellite controller to evaluate both power state and attitude during collections. The power-optimal system resulted in equal collection performance while ensuring a more power-positive state for the spacecraft but required greater maximum power input and greater overall computational cost. The power-optimal controller has direct application to small satellite earth imaging missions that are often power constrained due to non-articulated solar arrays and relatively small power storage capacity.
Power-Optimal Slew Maneuvers in Support of Small Satellite Earth Imaging Missions
Utah State University, Logan, UT
Small satellite image collection missions typically rely on commercial, off-the-shelf products with control systems that use established methods for managing spacecraft attitude operations. Controllers in this marketplace simply move the spacecraft between commanded orientations without considering solar exposure. In particular, performing a specified slew based on traditional methods may keep solar arrays in shadow, draining the satellite’s power. To compensate, satellite operation teams often command the vehicle to enter a “sunbathe” state between collections. This additional level of complexity requires manual or rigidly prescribed specification of the frequency and duration of the “sunbathe” operation. However, there is opportunity for power collection during movement if satellite slews are controlled to optimize solar exposure in combination with control input. This paper describes development of a novel satellite slew maneuvering controller that optimizes satellite power state. By controlling reaction wheel accelerations and orienting solar arrays during slew maneuvers, opportunities for both image collection and power collection and consumption are considered. The controller reduces the need for operator decisions by integrating power collection with imaging tasks. This approach first prioritizes several image collection targets using an image collection score and slew cost in discretized time to generate a directed acyclic graph. The optimal collection path through the graph is then computed to generate a representative slew plan for the power state optimal controller. In simulation of several scenarios, satellite behavior reflected power-prioritized objectives while achieving collection requirements. Performance of the power-optimal controller was compared with a standard small satellite controller to evaluate both power state and attitude during collections. The power-optimal system resulted in equal collection performance while ensuring a more power-positive state for the spacecraft but required greater maximum power input and greater overall computational cost. The power-optimal controller has direct application to small satellite earth imaging missions that are often power constrained due to non-articulated solar arrays and relatively small power storage capacity.
