Star-tracker-based attitude determination for spinning spacecraft
A method of determining the attitude of a spinning spacecraft is provided. The method includes stabilizing the spacecraft, initializing the attitude of the spacecraft using star tracker data, and estimating the attitude of the spacecraft.
1. A method of estimating the attitude of a spacecraft, in transfer orbit, spinning at a rate of substantially in the range of 0.3 degrees per second to 1.5 degrees per second, comprising the steps of:
stabilizing the spinning spacecraft;
simultaneously adjusting at least one of the spacecraft attitude and angular velocity so that enough power is available for spacecraft functionality;
simultaneously initializing the attitude of the spinning spacecraft, using star tracker data, in a power-safe and thermally-safe configuration; and
simultaneously estimating the attitude of the spinning spacecraft.
2. The method of claim 1 , wherein stabilizing the spinning spacecraft includes use of a control law referenced to an inertial frame with a fixed offset to an earth centered inertial frame.
3. The method of claim 1 , wherein stabilizing the spinning spacecraft includes use of a 3-axis stabilized controller.
4. The method of claim 1 , wherein stabilizing the spinning spacecraft includes controlling the spacecraft to a stable rotation by a rate-only controller.
5. The method of claim 4 , wherein controlling the spinning spacecraft to a stable rotation includes a substantially zero rate rotation.
6. The method of claim 1 , wherein initializing the attitude of the spinning spacecraft using star tracker data comprises the steps of:
acquiring the attitude of the spinning spacecraft using star tracker measured data; and
validating the acquired attitude.
7. The method of claim 6 , wherein acquiring the attitude of the spinning spacecraft using star tracker data further includes the use of an inertial measurement unit.
8. The method of claim 6 , wherein acquiring the attitude includes matching of star patterns.
9. The method of claim 6 , wherein validating the acquired attitude includes consistency checks of multiple acquired attitudes estimated by the star tracker measured data.
10. The method of claim 9 , wherein the consistency checks of multiple acquired attitudes includes determining that multiple attitudes, acquired at different times, are consistent with the estimated angular velocity of the spinning spacecraft, or are consistent with the relative orientation of the separate star trackers from which the star tracker measured data was obtained.
11. The method of claim 6 , wherein validating the acquired attitude includes determining that measured solar panel current is sufficiently close to solar panel current predicted, using the acquired attitude.
12. The method of claim 6 , wherein validating the acquired attitude includes determining that measured solar sensor data is sufficiently close to sun sensor data predicted, using the acquired attitude.
13. The method of claim 6 , wherein validating the acquired attitude includes consistent matching of a measured sensor data and its predicted sensor data using acquired attitude.
14. The method of claim 1 , wherein estimating the attitude comprises steps of:
propagating the attitude to real time;
updating the attitude periodically; and
monitoring the spacecraft attitude.
15. The method of claim 14 , wherein propagating the attitude to real time includes the use of an inertial measurement unit.
16. The method of claim 14 , wherein propagating the attitude to real time includes use of star tracker estimated rate.
17. The method of claim 16 , wherein the star tracker estimated rate includes the use of a Kalman filter.
18. The method of claim 14 , wherein updating the attitude further includes updating the parameters associated with an inertial measurement unit.
19. The method of claim 14 , wherein updating includes using of acquired attitude.
20. The method of claim 14 , wherein updating includes using a star tracker measurement residual.
21. The method of claim 14 , wherein updating includes the use of a Kalman filter.
22. The method of claim 14 , wherein monitoring the spacecraft attitude includes one or more of: acquiring the attitude of the spacecraft using star tracker measured data and validating the acquired attitude.
23. The method of claim 14 , wherein monitoring the spacecraft attitude includes checking that a star tracker measurement residual is below a threshold before each updating.
24. The method of claim 14 , wherein monitoring the spacecraft attitude includes use of the trending of parameters of an inertial measurement unit.
25. A method of estimating the attitude of a spacecraft, in transfer orbit, spinning at a rate of substantially in the range of 0.3 degrees per second to 1.5 degrees per second, comprising:
stabilizing the spinning spacecraft;
simultaneously acquiring spacecraft attitude using star tracker measured data;
simultaneously adjusting at least one of the spacecraft attitude and angular velocity so that enough power is available for spacecraft functionality;
simultaneously configuring the spinning spacecraft so that it is power-safe and thermally-safe;
simultaneously propagating the spacecraft attitude to real time; and
simultaneously updating the spacecraft attitude periodically.
26. A method of operating a spacecraft spinning at a rate of substantially in the range of 0.3 degrees per second to 1.5 degrees per second in a transfer orbit, comprising:
stabilizing the spinning spacecraft;
simultaneously adjusting at least one of the spacecraft attitude and angular velocity so that enough power is available for spacecraft functionality;
simultaneously configuring the spinning spacecraft so that it is power-safe and thermally-safe;
simultaneously estimating the attitude of the spinning spacecraft using star tracker data; and
simultaneously maneuvering the spinning spacecraft by an attitude controller using the estimated attitude.
27. The method of claim 26 , wherein stabilizing the spinning spacecraft includes use of a control law referenced to an inertial frame with a fixed offset to an earth centered inertial frame.
28. The method of claim 26 , wherein stabilizing the spinning spacecraft includes controlling the spinning spacecraft to a stable rotation by a rate-only controller.
29. The method of claim 26 , wherein estimating the attitude of the spinning spacecraft using star tracker data comprises the steps of:
acquiring the attitude of the spinning spacecraft using star tracker data;
validating the acquired attitude;
propagating the attitude to real time;
updating the attitude periodically; and
monitoring the attitude.
30. The method of claim 29 , wherein acquiring the attitude of the spinning spacecraft using star tracker data further includes the use of an inertial measurement unit.
31. The method of claim 29 , wherein validating the acquired attitude includes consistency checks of multiple acquired altitudes estimated by the star tracker measured data.
32. The method of claim 29 , wherein validating the acquired attitude includes determining that measured solar panel current is sufficiently close to solar panel current predicted using the acquired attitude.
33. The method of claim 29 , wherein validating the acquired attitude includes determining that measured sun sensor data is sufficiently close to sun sensor data predicted using the acquired attitude.
34. The method of claim 29 , wherein propagating the attitude to real time includes the use of an inertial measurement unit.
35. The method of claim 29 , wherein propagating the attitude to real time includes use of star tracker estimated rate.
36. The method of claim 29 , wherein updating the attitude further includes updating the parameters associated with an inertial measurement unit.
37. The method of claim 29 , wherein monitoring the spinning spacecraft attitude includes one or more of acquiring the attitude of the spinning spacecraft using star tracker measured data and validating the acquired attitude.
38. The method of claim 29 , wherein monitoring the spinning spacecraft attitude includes checking that a star tracker measurement residual is below a threshold before each updating.
39. The method of claim 29 , wherein monitoring the spinning spacecraft attitude includes use of the trending of parameters associated with an inertial measurement unit.
40. The method of claim 26 , wherein maneuvering the spinning spacecraft by a controller using the estimated attitude includes a reorientation maneuver.
41. The method of claim 26 , wherein maneuvering the spinning spacecraft by a controller using the estimated attitude includes a spin speed change.
42. The method of claim 26 , wherein maneuvering the spinning spacecraft by a controller using the estimated attitude includes a motor burn.