REFINING A POSITION ESTIMATE OF A LOW EARTH ORBITING SATELLITE

• US 20090182502A1
• Filed: 12/16/2008
• Published: 07/16/2009
• Est. Priority Date: 01/10/2008
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Talbot, Nicholas C., Riter, Bruce D., Janky, James M., Vollath, Ulrich
• Granted Patent: US 8,260,551 B2
• Time in Patent Office: Days
• US Class Current: 701/214
• CPC Class Codes: G01S 19/07 providing data for correcting measured positioning data, e.g. DGPS [differential GPS] or ionosphere corrections
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude

Abstract

In a method for refining a position estimate of a low earth orbiting (LEO) satellite a first position estimate of a LEO satellite is obtained with a GNSS receiver on-board the LEO satellite. The first position estimate is communicated to a Virtual Reference Station (VRS) processor. VRS corrections are received at the LEO satellite, the VRS corrections having been calculated for the first position estimate by the VRS processor. The VRS corrections are processed on-board the LEO satellite such that a VRS corrected LEO satellite position estimate of the LEO satellite is generated for the first position estimate.

Claims

1. A method for refining a position estimate of a low earth orbiting (LEO) satellite:

obtaining a first position estimate of a LEO satellite with a GNSS receiver on-board said LEO satellite;

communicating said first position estimate to a Virtual Reference Station (VRS) processor;

receiving VRS corrections at said LEO satellite, said VRS corrections calculated for said first position estimate by said VRS processor; and

processing said VRS corrections on-board said LEO satellite such that a VRS corrected LEO satellite position estimate of said LEO satellite is generated for said first position estimate.

2. The method as recited in claim 1, wherein said obtaining a first position estimate of a LEO satellite with a GNSS receiver on-board said LEO satellite comprises:

receiving signals from a plurality of GNSS satellites, said signals comprising GNSS observables measured by said GNSS receiver; and

generating said first position estimate from said signals using said GNSS receiver.

3. The method as recited in claim 1, wherein said communicating said first position estimate to a VRS processor comprises:

transmitting said first position estimate using a telemetry downlink to communicate said first position estimate from said LEO satellite, wherein said downlink is further coupled to a communications network configured for delivering said first position estimate to said VRS processor.

4. The method as recited in claim 1, wherein said communicating said first position estimate to a VRS processor comprises:

formatting said first position estimate into a GNSS information message along with an identifier associated with said LEO satellite; and

communicating said GNSS information message to said VRS processor.

5. The method as recited in claim 1, wherein said receiving VRS corrections at said LEO satellite comprises:

receiving said VRS corrections utilizing a telemetry uplink of said LEO satellite, wherein said telemetry uplink is communicatively coupled with said VRS processor.

6. The method as recited in claim 1, wherein said processing said VRS corrections on-board said LEO satellite such that a VRS corrected LEO satellite position estimate of said LEO satellite is generated for said first position estimate comprises:

processing said VRS corrections to correct for errors in GNSS observables measured by said GNSS receiver.

7. The method as recited in claim 1, further comprising:

transmitting said VRS corrected LEO satellite position estimate from said LEO satellite for receipt by a GNSS rover receiver.

8. The method as recited in claim 7, wherein said transmitting said VRS corrected LEO satellite position estimate from said LEO satellite for receipt by a GNSS rover receiver comprises:

transmitting said VRS corrected LEO satellite position estimate over a communications channel of said LEO satellite for receipt by a terrestrial GNSS rover receiver, said GNSS rover receiver being configured with a LEO compatible receiver for reception of said LEO corrected satellite position estimate.

9. The method as recited in claim 1, further comprising:

utilizing said VRS corrected LEO position estimate as an input to an orbit control system of said LEO satellite.

10. A positioning and navigation system comprising:

a global navigation satellite system (GNSS) receiver, coupled with a Low Earth Orbiting (LEO) satellite and configured for measuring GNSS broadcast observables for use in generating a first position estimate indicative of an approximate position of said LEO satellite;

a virtual reference station (VRS) processor, configured for processing broadcast observables received from a plurality of GNSS receivers including a plurality of GNSS reference receivers, to generate VRS corrections for said first position estimate; and

a corrections processor for processing said VRS corrections on-board said LEO satellite such that a VRS corrected LEO satellite position estimate is produced.

11. The system of claim 10, further comprising

a GNSS information formatter coupled with said GNSS receiver on-board said LEO satellite and configured for formatting said first position estimate and an identifier associated with said LEO satellite into a GNSS information message for communication from said LEO satellite to said VRS processor.

12. The system of claim 10, wherein said VRS processor is further configured for generating a corrections message comprising said VRS corrections for said first position estimate.

13. The system of claim 10, further comprising:

a first communications path configured for transmission of said first position estimate from said LEO satellite to said VRS processor for use in generating said VRS corrections.

14. The system of claim 13, wherein said first communications path comprises:

a telemetry downlink between said LEO satellite and a control station for said LEO satellite; and

a communicative coupling between said control station and said VRS processor.

15. The system of claim 13, further comprising:

a second communications path configured for transmitting a VRS corrections message between said VRS processor and said LEO satellite, said VRS corrections message comprising said VRS corrections.

16. The system of claim 15, wherein said second communications path comprises:

a communicative coupling between said VRS processor and a control station for said LEO satellite; and

a telemetry uplink between said control station and said LEO satellite.

17. The system of claim 13, further comprising:

a third communications path configured for transmitting said VRS corrected LEO satellite position estimate to a GNSS rover receiver, wherein said third communication path comprises a LEO satellite downlink communications channel.

18. A low earth orbiting (LEO) satellite position determination system, said system comprising:

a global navigation satellite system (GNSS) receiver coupled with a LEO satellite, and configured for measuring GNSS broadcast observables for use in generating a first position estimate indicative of an approximate position of said LEO satellite;

a communications subsystem of said LEO satellite, configured for transmitting a first radio frequency message comprising said first position estimate, said first position estimate being conveyed to a VRS processor for use in generating VRS corrections;

said communications subsystem further configured for receiving a second radio frequency message comprising a corrections message generated by said VRS processor, said corrections message comprising said VRS corrections; and

a corrections processor for processing a received corrections message on-board said LEO satellite such that a VRS corrected LEO satellite position estimate is generated.

19. The system of claim 18, further comprising

a GNSS information formatter coupled with said GNSS receiver on-board said LEO satellite and configured for formatting said first position estimate and an identifier associated with said LEO satellite into a GNSS information message for communication from said LEO satellite to said VRS processor.

20. The system of claim 18, further comprising:

a communicative coupling between said corrections processor and an orbit control subsystem of said LEO satellite, said communicative coupling for providing said VRS corrected LEO satellite position estimate as an input to said orbit control subsystem.

21. The system of claim 18, wherein said communications subsystem is further configured for transmitting said VRS corrected LEO satellite position estimate from said LEO satellite for receipt by a GNSS rover receiver.

22. The system of claim 21, wherein said rover receiver comprises a space borne GNSS receiver.

23. The system of claim 21, wherein said GNSS rover receiver comprises a terrestrial GNSS rover receiver configured with a LEO receiver.

24. The system of claim 21, wherein said GNSS rover receiver comprises a subscribed client, wherein said LEO corrected satellite position estimate is transmitted by said antenna system to said subscribed client in exchange for a fee.