Spacecraft gyro calibration system

• US 7,185,858 B2
• Filed: 11/26/2003
• Issued: 03/06/2007
• Est. Priority Date: 11/26/2003
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Wang, Hangching Grant, Li, Rongsheng K
• Primary Examiner(s): Carone; Michael J.
• Assistant Examiner(s): Holzen; Stephen A
• Application Number:
  US10/723,782
• Publication Number:
  US 20050108884A1
• Time in Patent Office: 1,196 Days
• Field of Search: 244/158.1, 244/158.4, 244/158.5, 244/158.6, 244/164, 244/171, 731/78, 318580-590, 701 3- 20
• US Class Current: 244/171
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

A method of calibrating a gyro (42) of a spacecraft (14) may include determining a yaw attitude residual of the spacecraft. Roll gyro bias residual is determined in response to the yaw attitude residual. The gyro (42) is calibrated in response to the roll gyro bias residual. A method of calibrating a gyro (42) of a spacecraft (14) may alternatively include disabling gyro calibration, gain scheduling, or resetting attitude and gyro bias covariance, for selective axes, for a yaw transient period. The gyro (42) is calibrated in a nominal fashion after completion of the yaw transient period.

Claims

1. A method of calibrating a gyro of a spacecraft comprising:

determining a yaw attitude residual from a first yaw attitude measured by attitude sensors including a sun sensor to determine absolute yaw attitude of the spacecraft when the sun comes in a field of view of the sun sensor, and subtracting from the measured first yaw attitude a second yaw attitude estimated by gyro compassing when the sun is not in a field of view of the sun sensor;

converting the difference yaw attitude residual into a roll gyro bias residual; and

calibrating the gyro in response to said converted roll gyro bias residual.

2. The method as in claim 1 further comprising adjusting an update gain of said roll gyro bias residual in response to a thermal model estimation.

3. The method as in claim 2 wherein adjusting an update gain of said roll gyro bias residual comprises determining said update gain via a Kalman filter.

4. The method as in claim 1 further comprising calibrating the gyro at a first periodic rate during an initialization period and calibrating the gyro at a second periodic rate upon expiration of said initialization period.

5. The method as in claim 1 further comprising summing said roll gyro bias residual with a previous roll gyro bias estimation to generate a current roll gyro bias estimation.

6. The method as in claim 1 wherein calibrating the gyro is implemented via on-board flight software.

7. A method as in claim 1 wherein calibrating the gyro is implemented via ground based operational software.

8. The method as in claim 1 wherein calibrating the gyro is performed approximately once per orbit and near a beginning portion of a gyro calibration period.

9. The method as in claim 1 wherein calibrating the gyro is performed using at least one yaw attitude signal sample per orbit near a beginning portion of a gyro calibration period.

10. The method as in claim 1 wherein said yaw attitude residual is determined by measuring a plurality of second yaw attitude signal samples per orbit near a beginning portion of a gyro calibration period.

11. The method as in claim 10 further comprising using a weighted averaging of said plurality of second yaw attitude signal samples.

12. A method of reorienting a spacecraft comprising:

determining a first yaw attitude of the spacecraft by attitude sensors measurements including a sun sensor to determine absolute yaw attitude of the spacecraft when the sun is in a field of view of the sun sensor;

determining a second yaw attitude of the spacecraft by gyro compassing when the sun is not in a field of view of the sun sensor;

determining a yaw attitude residual using the difference between said first yaw attitude and said second yaw attitude;

determining a roll gyro bias residual using said difference yaw attitude residual;

calibrating a roll gyro using said determined roll gyro bias residual;

estimating attitude of the spacecraft using said calibrated roll gyro; and

reorienting the spacecraft in response to said estimated attitude.

13. A method of calibrating a gyro of a spacecraft comprising:

determining attitude of the spacecraft measured during a yaw transient period by disabling yaw gyro calibration during the yaw transient period and;

determining a first yaw attitude of the spacecraft by attitude sensors measurements including a sun sensor to determine absolute yaw attitude of the spacecraft when the sun is in a field of view of the sun sensor;

determining a second yaw attitude of the spacecraft by gyro compassing when the sun is not in a field of view of the sun sensor;

determining a yaw attitude residual using the difference between said first yaw attitude and said second yaw attitude;

determining a roll gyro bias residual using said difference yaw attitude residual;

calibrating a roll gyro using said determined roll gyro bias residual;

estimating attitude of the spacecraft using said calibrated roll gyro; and

gain scheduling gyro calibration and attitude determination using at least partially said spacecraft attitude determined during the yaw transient period.

14. The method as in claim 13 wherein gain scheduling comprises using a gain scheduling signal during the yaw transient period.

15. The method as in claim 14 wherein using a gain scheduling signal comprises using a yaw transient error.

16. A method as in claim 14 wherein using a gain scheduling signal comprises using a sun sensor measurement.

17. A method as in claim 14 wherein using a gain scheduling signal comprises using ephemens.

18. The method as in claim 13 wherein gain scheduling comprises disabling said gyro calibration for at least one attitude axis during an initial period when the sun comes within a field of view of an associated sun sensor.

19. The method as in claim 13 wherein gain scheduling comprises disabling said gyro calibration for at least one attitude axis during a period when a yaw attitude error is greater than a predetermined value.

20. The method as in claim 13 wherein gain scheduling comprises disabling said gyro calibration for at least one attitude axis during said yaw transient period.

21. A method as in claim 13 wherein performing gain scheduling comprises varying gyro bias update gain for at least one attitude axis from low to nominal during said yaw transient period.

22. A method as in claim 13 wherein performing gain scheduling comprises varying attitude update gain of at least one attitude axis from high to nominal during said yaw transient period.

23. A method as in claim 13 wherein gain scheduling comprises resetting attitude covariance of at least one axis to a high value.

24. A method as in claim 13 wherein gain scheduling comprises resetting gyro covariance of at least one axis to a low value.