Spacecraft power acquisition method for wing-stowed configuration
A system for, and method of recovering a solar-powered spacecraft from an anomaly that renders the attitude of the spacecraft unknown includes maintaining a power-safe attitude by switching between two orthogonal axes using solar panel current sensors. The system and method may also include simultaneously determining spacecraft attitude using a star sensor. The system is applicable to spacecraft operating in a solar wing-stowed configuration.
1. A method of acquiring a power-safe state for a wing-stowed spacecraft with one or more exposed solar panels in a spinning transfer orbit, the method comprising:
a first rotation phase that includes maintaining a steady spin about a first axis that is substantially orthogonal to a direction that is normal to at least one of the exposed solar panels, sensing panel current from at least one of the exposed solar panels, and if the sensed solar panel peak current does not exceed a threshold current, stopping the first rotation at the peak current of one of the solar panels; entering a second rotation phase;
the second rotation phase including maintaining a steady spin about a second axis that is substantially orthogonal to the direction that is normal to at least one of the exposed solar panels, and that is substantially orthogonal to the first axis, and sensing panel current from at least one of the exposed solar panels, and if the sensed solar panel peak current does not exceed a threshold current, stopping the second rotation at the peak current of one of the solar panels, and entering the first rotation phase.
2. The method of claim 1 , wherein the first axis is the z-axis of the spacecraft.
3. The method of claim 1 wherein the second axis is the x-axis of the spacecraft.
4. The method of claim 1 , wherein the first rotation phase and the second rotation phase use thrusters for attitude control.
5. The method of claim 1 , wherein the first rotation phase and the second rotation phase use a set of reaction wheels for attitude control.
6. The method of claim 1 , wherein the first rotation and the second rotation select a rotation direction and a rotation rate such that the reaction wheels will not be saturated.
7. The method of claim 1 , wherein the first rotation phase and the second rotation phase use thrusters to dump momentum to facilitate attitude control by reaction wheels.
8. The method of claim 1 , wherein the peak current is determined by a peak current finding algorithm.
9. The method of claim 1 , wherein stopping the rotation at peak current is performed by resetting the commanded and estimated attitude quaternions to identity at peak current.
10. A method of acquiring a power-safe state for a wing-stowed spacecraft in a spinning transfer orbit that has one or more exposed solar panels, the method comprising:
entering a first rotation phase that includes maintaining a steady spin about a first axis that is substantially orthogonal to a direction that is normal to at least one of the exposed solar panels;
acquiring spacecraft attitude using one or more star trackers;
sensing panel current from at least one of the exposed solar panels, and if the sensed solar panel peak current does not exceed a threshold current, stopping the first rotation at the peak current of at least one of the solar panels and entering a second rotation phase, the second rotation phase including maintaining a steady spin about a second axis that is substantially orthogonal to the direction that is normal to at least one of the exposed solar panels, and that is substantially orthogonal to the first axis; and
maneuvering the spacecraft to a predetermined power-safe attitude after the spacecraft attitude has been acquired.
11. The method of claim 10 , wherein the first axis is the z-axis of the spacecraft.
12. The method of claim 10 , wherein the second axis is the x-axis of the spacecraft.
13. The method of claim 10 , wherein the stopping the first rotation at the peak current uses solar panel current to determine body spin phase.
14. The method of claim 10 , wherein the first rotation phase, the second rotation, and maneuvering include the use of thrusters for attitude control.
15. The method of claim 10 , wherein the first rotation phase, the second rotation, and maneuvering include the use of a set of reaction wheels.
16. The method of claim 10 , wherein maneuvering the spacecraft to a predetermined power-safe attitude includes maneuvering an axis in the x/z plane of the spacecraft body to be equatorial normal.