Geosynchronous spacecraft autonomous navigation

• US 7,860,617 B1
• Filed: 07/24/2007
• Issued: 12/28/2010
• Est. Priority Date: 07/24/2007
• Status: Active Grant

• Current Assignee: Emergent Technologies Corporation, Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Emergent Technologies Corporation, Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Gaylor, David, Bamford, William, Weigl, Harald J., Goodzeit, Neil E.
• Primary Examiner(s): Collins; Timothy D
• Assistant Examiner(s): BENEDIK, JUSTIN M
• Application Number:
  US11/878,359
• Time in Patent Office: 1,253 Days
• Field of Search: 244/158.4, 244/164, 244/165, 702/176, 701/213, 701/214
• US Class Current: 701/13
• CPC Class Codes: B64G 1/244 Spacecraft control systems

Abstract

A spacecraft system is provided, including a measurement device configured to measure information associated with position of a spacecraft, a filter configured to process the measured information and to provide estimated pre-maneuver information associated with position of the spacecraft and estimated post-maneuver information associated with position of the spacecraft, a propagator configured to predict post-maneuver information associated with position of the spacecraft based upon the estimated pre-maneuver information associated with position of the spacecraft and a model of a maneuver of the spacecraft, an error calculator configured to calculate an acceleration error based upon the estimated post-maneuver information associated with position of the spacecraft and the predicted post-maneuver information associated with position of the spacecraft, and a maneuver archive configured to store the acceleration error for updating the model of the maneuver. The filter, the propagator, the error calculator and the maneuver archive may be implemented in software and/or onboard the spacecraft.

Claims

1. A spacecraft system comprising:

a measurement device configured to measure information associated with position of a spacecraft;

a filter configured to process the measured information and to provide estimated pre-maneuver information associated with position of the spacecraft and estimated post-maneuver information associated with position of the spacecraft;

a propagator configured to predict post-maneuver information associated with position of the spacecraft based upon the estimated pre-maneuver information associated with position of the spacecraft and a model of a maneuver of the spacecraft;

an error calculator configured to calculate an acceleration error using a state transition matrix, the acceleration error based upon the estimated post-maneuver information associated with position of the spacecraft and the predicted post-maneuver information associated with position of the spacecraft; and

a maneuver archive configured to store the acceleration error for updating the model of the maneuver,

wherein the state transition matrix is identified by Φ

(t_s,t_m) and satisfies the following relationship;

2. The spacecraft system of claim 1, wherein each of the measured information, the estimated pre-maneuver information, the estimated post-maneuver information and the predicted post-maneuver information includes one or more of:

a position of the spacecraft and a velocity of the spacecraft.

3. The spacecraft system of claim 1, wherein the filter is an Extended Kalman Filter (“

EKF”

).

4. The spacecraft system of claim 1, wherein the propagator is an orbital propagator.

5. The spacecraft system of claim 1, wherein the filter, the propagator, the error calculator and the maneuver archive are implemented in software.

6. The spacecraft system of claim 1, further comprising the spacecraft.

7. The spacecraft system of claim 1, wherein the filter, the propagator, the error calculator and the maneuver archive are implemented onboard the spacecraft.

8. The spacecraft system of claim 1, wherein the spacecraft is in a geosynchronous orbit.

9. The spacecraft system of claim 1, wherein the measurement device is a GPS receiver onboard the spacecraft.

10. The spacecraft system of claim 1, wherein the error calculator is further configured to multiply the acceleration error by a weighting variable K before the model of the maneuver is updated.

11. The spacecraft system of claim 10, wherein K is between 0.25 and 0.75.

12. The spacecraft system of claim 1, wherein the spacecraft includes one or more thrusters, and wherein the model of the maneuver includes performance information about the one or more thrusters.

13. A system for calibrating spacecraft maneuvers comprising a processor configured to receive information associated with position of a spacecraft having one or more thrusters, to provide estimated pre-maneuver position-related information about the spacecraft and estimated post-maneuver position-related information about the spacecraft, to predict post-maneuver position-related information about the spacecraft based upon the estimated pre-maneuver position-related information about the spacecraft and a model of a maneuver of the spacecraft, the model of the maneuver of the spacecraft including performance information about the one or more thrusters, to calculate an acceleration error using a state transition matrix, and to update the model of the maneuver, wherein the acceleration error is based upon the estimated post-maneuver position-related information about the spacecraft and the predicted post-maneuver position-related information about the spacecraft,

wherein the state transition matrix is identified by Φ

(t_s,t_m) and satisfies the following relationship;

14. The system of claim 13, wherein the information associated with position of about the spacecraft includes one or more of:

a position of the spacecraft and a velocity of the spacecraft.

15. A method for calibrating spacecraft maneuvers, comprising the steps of:

generating, with a filter, estimated pre-maneuver information associated with position of a spacecraft;

predicting, with a propagator, post-maneuver information associated with position of the spacecraft based upon the estimated pre-maneuver information associated with position and a model of a maneuver;

performing the maneuver;

generating, with the filter, estimated post-maneuver information associated with position of the spacecraft;

calculating an acceleration error using a state transition matrix, the acceleration error based upon a difference between the estimated post-maneuver information associated with position and the predicted post-maneuver information associated with position; and

updating the model of the maneuver based upon the calculated acceleration error,

wherein the state transition matrix is identified by Φ

(t_s,t_m) and satisfies the following relationship;

16. The method of claim 15, wherein each of the estimated pre-maneuver information, the estimated post-maneuver information and the predicted post-maneuver information includes one or more of:

a position of the spacecraft and a velocity of the spacecraft.

17. The method of claim 15, wherein the filter is an Extended Kalman Filter (“

EKF”

).

18. The method of claim 15, wherein the propagator is an orbital propagator.

19. The method of claim 15, wherein the estimated pre-maneuver position and velocity information and the estimated post-maneuver position and velocity information are generated based on GPS receiver measurements of position and velocity of the spacecraft.

20. The method of claim 15, wherein the filter and the propagator are implemented in software.

21. The method of claim 15, wherein the filter and the propagator are implemented onboard the spacecraft.

22. The method of claim 15, wherein the calculating the acceleration error and the updating the model are performed onboard the spacecraft.

23. The method of claim 15, wherein updating the model of the maneuver includes modifying the model by a weighting fraction K of the calculated acceleration error.

24. The method of claim 15, wherein the model of the maneuver includes performance information about one or more thrusters of the spacecraft.