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Avoiding the burn: Maintaining a Sun-safe attitude for the Solar Probe Plus spacecraft
Author | Vaughan, Robin; Kubota, Sanae; Shapiro, Hongxing; Kagan, Mike; Vesel, John; |
Keywords | Attitude control; Closed loop control systems; Failure analysis; Probes; Solar cell arrays; Spacecraft; Parker Engineering |
Abstract | The Solar Probe Plus (SPP) mission plans to send a spacecraft to explore the inner region of the heliosphere and is currently working towards launch in 2018. The SPP spacecraft will make in-situ measurements and remote observations over a series of 24 nearly-ecliptic solar orbits with perihelion decreasing from 35 solar radii (Rs) to a minimum of 9.86 Rs over a period of 7 years. Proper orientation of the spacecraft and solar arrays relative to the Sun is essential for a successful mission. A large shield must be kept between the main body of the spacecraft and the Sun for most of the mission when the spacecraft is within 0.7 AU of the Sun. The bulk of the fault management effort for SPP focuses on maintaining a Sun-safe attitude and safe thermal conditions for the solar arrays and their active cooling system. This paper discusses aspects of the guidance and control (G&C) system designed to respond to conditions that could lead to spacecraft attitude deviations and how these interact with the overall spacecraft fault management responses. Initial G&C modes of operation are identified based on different combinations of the available sensors and actuators. The design and operation of solar limb sensors, customized to provide an external detection of off-nominal attitude at close solar distances, is described. Examples of attitude control using the solar limb sensor measurements are presented. Tolerance to short-duration interruptions of closed-loop control from high-level safing responses is investigated. Results of initial simulations show that attitude deviations can be corrected in sufficient time to prevent unwanted solar illumination of spacecraft bus components intended to remain in the shadow of the thermal protection shield. |
Year of Publication | 2013 |
Journal | AIAA Guidance, Navigation, and Control (GNC) Conference |
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Number of Pages | Draper Laboratory - |
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