Spacecraft orbit control using orbit position feedback

• US 6,508,438 B2
• Filed: 08/03/2001
• Issued: 01/21/2003
• Est. Priority Date: 08/13/1999
• Status: Expired due to Term

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Eyerly, Bruce N.
• Primary Examiner(s): Poon, Peter M.
• Assistant Examiner(s): JAKEL, KEVIN W
• Application Number:
  US09/921,737
• Publication Number:
  US 20020020785A1
• Time in Patent Office: 536 Days
• Field of Search: 244/158.R, 244/164, 244/171, 244/161, 701/13
• US Class Current: 244/164
• CPC Class Codes: B64G 1/242 Orbits and trajectories
• CPC Class Codes: B64G 1/2427 Transfer orbits
• CPC Class Codes: B64G 1/26 using jets

Abstract

A spacecraft orbit control system and method for controlling the orbit of a spacecraft during orbit raising includes processing spacecraft position data to meet the spacecraft attitude sensing needs for long duration, low thrust orbit raising burns. The actual spacecraft position as determined by a global positioning system (GPS) receiver is compared with the desired spacecraft position to generate an error signal indicative of a spacecraft position error for adjusting the attitude of the spacecraft as thrusters move the spacecraft. The attitude of the spacecraft is adjusted to eliminate the spacecraft position error such that the actual spacecraft position corresponds with the desired spacecraft position and the spacecraft maintains a desired orbit during the orbit raising.

Claims

1. A control system for controlling the orbit of a spacecraft during orbit raising, the control system comprising:

an actual spacecraft position sensor generating an actual position signal;

a trajectory provider comprising;

an orbital determination provider generating an orbital model;

a memory containing information of a desired orbit;

a second comparator generating an orbital error signal in response to said desired orbit and said orbital model; and

a trajectory calculator determining a trajectory in response to said orbital error signal;

a desired spacecraft position provider generating a desired position signal representing a desired position along said trajectory;

a first comparator generating a positional error signal in response to said actual position signal and said desired position signal; and

a spacecraft attitude control system adjusting attitude of the spacecraft in response to said positional error signal.

2. A control system as in claim 1 wherein said spacecraft attitude control system adjusts attitude of the spacecraft such that the spacecraft maintains a desired orbit during orbit raising.

3. A control system as in claim 1 wherein said actual spacecraft position sensor contains a global positioning system receiver.

4. A control system as in claim 1 wherein said orbital determination provider determines a current orbit in response to said actual position signal.

5. A control system as in claim 1 wherein said orbital determination provider contains a model of a spacecraft orbit around earth.

6. A control system as in claim 1 further comprising a thruster oriented at a given attitude and providing a given level of thrust to adjust the attitude of the spacecraft.

7. A control system as in claim 6 wherein said thruster is a constant power thruster.

8. A control system as in claim 6 wherein said spacecraft attitude control system controls the attitude of the thruster to adjust the attitude of the spacecraft.

9. A control system as in claim 6 wherein said spacecraft attitude control system controls the thrust level of the thruster to adjust the attitude of the spacecraft.

10. A control system as in claim 6 wherein said thruster is adjusted by receiving a thruster adjustment signal from an earth station.

11. A control system as in claim 1 wherein said trajectory provider receives orbital information from an earth station.

12. A method for controlling the orbit of a spacecraft during orbit raising, the method comprising:

generating an actual position signal;

generating an orbital model;

comparing said orbital model with a desired orbit to generate a orbital error signal;

determining a trajectory in response to said orbital error signal;

determining a desired position along said trajectory and generating a desired position signal;

comparing the actual position signal with the desired position signal to generate a positional error signal; and

adjusting attitude of the spacecraft in response to said position error signal.

13. A method as in claim 12 wherein generating an actual position signal includes using a global positioning system receiver.

14. A method as in claim 12 wherein adjusting the attitude of the spacecraft includes controlling the attitude of a thruster.

15. A method as in claim 14 wherein adjusting the attitude of the spacecraft comprises powering said thruster at a constant power.

16. A method as in claim 15 wherein adjusting the attitude of the spacecraft comprises:

powering said thruster at a low thrust level; and

incrementally powering said thruster until the spacecraft is in a desired position.

17. A method as in claim 12 further comprising determining efficient times to power “

ON”

thrusters during orbit raising.

18. A method as in claim 12 wherein generating an actual position signal is performed periodically.

19. A control system for controlling the orbit of a low earth orbit (LEO) spacecraft during orbit raising, the spacecraft having a thruster oriented at a given attitude and providing a given level of thrust to move the spacecraft, the control system comprising:

an actual spacecraft position sensor generating an actual position signal;

a trajectory provider comprising;

an orbital determination provider generating an orbital model;

a memory containing information of a desired orbit;

a second comparator generating an orbital error signal in response to said desired orbit and said orbital model; and

a trajectory calculator determining a trajectory in response to said orbital error signal;

a desired spacecraft position provider generating a desired position signal representing a desired position along said trajectory;

a first comparator generating an positional error signal in response to said actual position signal and said desired position signal; and

a spacecraft attitude control system adjusting attitude of the thruster as to adjust attitude of the spacecraft in response to said positional error signal while maintaining a desired orbit during the orbit raising.

20. A control system as in claim 19 wherein said orbital determination provider contains a model of a spacecraft orbit around earth.