SATELLITE NAVIGATION USING LONG-TERM NAVIGATION INFORMATION

• US 20080154502A1
• Filed: 12/22/2006
• Published: 06/26/2008
• Est. Priority Date: 12/22/2006
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Tekawy, Jonathan A., Kelley, Clifford W., DiEsposti, Raymond S.
• Granted Patent: US 8,676,501 B2
• Time in Patent Office: Days
• US Class Current: 701/226
• CPC Class Codes: G01S 19/02 Details of the space or ground control segments
• CPC Class Codes: G01S 19/05 providing aiding data

Abstract

An improved approach to satellite-based navigation (e.g., GPS) is provided. In one embodiment, a method includes receiving a first set of tracking information. A nominal orbital path for the navigation satellite is determined using the first set of tracking information. Ephemeris data corresponding to the nominal orbital path is computed and uploaded to the navigation satellite. Long-term navigation information corresponding to the nominal orbital path is transmitted to a communication system for broadcast to a plurality of navigation devices. A second set of tracking information is received, an orbital path of the navigation satellite using the second set of tracking information is predicted, and a difference between the predicted orbital path and the nominal orbital path is determined. Commands configured to instruct the navigation satellite to adjust an actual orbital path of the navigation satellite to substantially conform to the nominal orbital path are uploaded to the navigation satellite.

Claims

1. A method of adjusting a navigation satellite orbit, the method comprising:

receiving a first set of tracking information for a navigation satellite;

determining a nominal orbital path for the navigation satellite using the first set of tracking information;

computing ephemeris data corresponding to the nominal orbital path;

uploading the ephemeris data to the navigation satellite;

transmitting long-term navigation information corresponding to the nominal orbital path to a communication system for broadcast to a plurality of navigation devices;

receiving a second set of tracking information for the navigation satellite;

predicting an orbital path of the navigation satellite using the second set of tracking information;

determining a difference between the predicted orbital path and the nominal orbital path; and

uploading commands to the navigation satellite, wherein the commands are configured to instruct the navigation satellite to adjust an actual orbital path of the navigation satellite to substantially conform to the nominal orbital path.

2. The method of claim 1, wherein the determining comprises:

selecting a set of predicted forces affecting orbital motion of the navigation satellite; and

numerically integrating differential equations of motion corresponding to the predicted forces starting from an initial condition to generate the nominal orbital path for the navigation satellite.

3. The method of claim 2, wherein the commands are configured to instruct the navigation satellite to adjust the actual orbital path to substantially compensate for deviations from the nominal orbital path caused by unpredicted forces.

4. The method of claim 2, wherein the selecting is performed to control propellant consumption by the navigation satellite.

5. The method of claim 2, wherein the selecting is performed to reduce periodic navigation station keeping maneuvers.

6. The method of claim 1, wherein the long-term navigation information is the ephemeris data.

7. The method of claim 1, wherein the long-term navigation information is state vector data.

8. The method of claim 7, wherein the state vector data comprises models of earth gravity, earth harmonics, earth tides, moon gravity, sun gravity, solar radiation pressure, and predicted satellite trajectory effects based on application of translational control forces.

9. The method of claim 1, further comprising repeating the method for a plurality of additional navigation satellites.

10. The method of claim 1, further comprising repeating the uploading at intervals of approximately 24 hours.

11. The method of claim 1, further comprising repeating the transmitting at intervals greater than approximately 24 hours.

12. The method of claim 1, wherein the communication system is the Internet.

13. The method of claim 1, wherein the communication system is a wireless communication system.

14. A method of providing satellite-based navigation at a navigation device, the method comprising:

receiving long-term navigation information from a communication system, wherein the long-term navigation information is associated with a nominal orbital path of a navigation satellite;

estimating a position of the navigation satellite using the long-term navigation information;

repeating the receiving and the estimating operations for a plurality of additional navigation satellites using long-term navigation information associated with each of the additional navigation satellites; and

determining a position of the navigation device based on the estimated positions of the navigation satellite and the additional navigation satellites.

15. The method of claim 14, wherein the long-term navigation information is ephemeris data corresponding to the nominal orbital path.

16. The method of claim 14, wherein the long-term navigation information is state vector data.

17. The method of claim 16, wherein the state vector data comprises models of earth gravity, earth harmonics, earth tides, moon gravity, sun gravity, solar radiation pressure, and predicted satellite trajectory effects based on application of translational control forces.

18. The method of claim 14, further comprising:

receiving ephemeris data from the navigation satellite, wherein the ephemeris data corresponds to the nominal orbital path of the navigation satellite;

selecting the long-term navigation information received from the communication system or the ephemeris data received from the navigation satellite; and

estimating the position of the navigation satellite based on the selected long-term navigation information or the selected ephemeris data.

19. The method of claim 18, further comprising:

repeating the second receiving, the selecting, and the second estimating operations for the plurality of navigation satellites and long-term navigation information or ephemeris data associated with the plurality of navigation satellites; and

determining the position of the navigation device based on the estimated positions of the navigation satellites.

20. The method of claim 14, wherein the communication system is the Internet.

21. The method of claim 14, wherein the communication system is a wireless communication system.

22. The method of claim 14, wherein the method is performed by the navigation device pursuant to a fee-based service agreement.

23. A navigation satellite comprising:

a receive antenna adapted to receive a plurality of ephemeris data sets and commands, wherein the commands are configured instruct the navigation satellite to adjust an actual orbital path of the navigation satellite to substantially conform to a nominal orbital path;

a memory adapted to store the ephemeris data sets;

a transmit antenna adapted to transmit the ephemeris data sets to a plurality of navigation devices;

a plurality of propulsion actuators; and

a processor adapted to control the propulsion actuators in response to the commands.

24. The navigation satellite of claim 23, wherein the propulsion actuators are selected from the group consisting of:

ion propulsion actuators and electric propulsion actuators.

25. A navigation device comprising:

means for receiving long-term navigation information from a communication system, wherein the long-term navigation information is associated with nominal orbital paths of a plurality of navigation satellites; and

a processor adapted to;

estimate positions of the navigation satellites using the long-term navigation information, and

determine a position of the navigation device based on the estimated positions of the navigation satellites.

26. The navigation device of claim 25, further comprising:

means for receiving ephemeris data from the navigation satellites, wherein the ephemeris data corresponds to nominal orbital paths of the navigation satellites, wherein the processor is further adapted to;

compare the long-term navigation information received from the communication system to the ephemeris data received from the navigation satellites as a consistency check,

select the long-term navigation information received from the communication system or the ephemeris data received from the navigation satellites, and

estimate the positions of the navigation satellites based on the selected long-term navigation information or the selected ephemeris data.

27. The navigation device of claim 25, wherein the long-term navigation information is ephemeris data corresponding to the nominal orbital paths of the navigation satellites.

28. The navigation device of claim 25, wherein the long-term navigation information is state vector data.

29. The navigation device of claim 25, wherein the state vector data comprises models of earth gravity, earth harmonics, earth tides, moon gravity, sun gravity, solar radiation pressure, and predicted satellite trajectory effects based on application of translational control forces.