Satellite integrity monitor and alert

• US 6,850,187 B1
• Filed: 05/02/2003
• Issued: 02/01/2005
• Est. Priority Date: 03/22/2001
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Clark, Ronald H.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US10/428,489
• Time in Patent Office: 641 Days
• Field of Search: 342/357.06, 701/213, 455/12.1, 455/427
• US Class Current: 342/357.395
• CPC Class Codes: G01S 19/10 providing dedicated supplementary positioning signals
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2

Abstract

The present invention is a system for providing GPS users with a high level of confidence in the integrity and accuracy of received GPS signals. The system provides a means for each GPS satellite itself to verify the accuracy and/or integrity of its own operations by calculations and processing internal to the GPS satellite and by crosslink communications with other GPS satellites in the GPS constellation. After a GPS satellite verifies the accuracy and/or integrity of its own signals, the GPS satellite transmits an integrity message to all GPS users in view of the satellite. The integrity message can alert GPS users to a loss of integrity or accuracy in the GPS signals. Alternatively, the integrity message can contain information to correct errors in the GPS signals. The integrity message can be incorporated into the existing GPS navigation message transmitted by GPS satellites, or the integrity message can be transmitted over a separate channel such as the planned L5 band channel.

Claims

1. A method for verifying the integrity of a navigation message transmitted from a Global Positioning System (GPS) satellite, comprising:

monitoring the integrity of a GPS navigation message produced by a first GPS satellite, the monitoring performed by the first GPS satellite or a second GPS satellite; and

broadcasting a GPS integrity message from the first GPS satellite to GPS users in-view of the satellite, wherein the GPS integrity message indicates the integrity of the GPS navigation message produced by the first GPS satellite;

wherein the monitoring comprises;

receiving the GPS navigation message at a receiver on the first GPS satellite;

checking the integrity of the GPS navigation message by

comparing the GPS navigation message with a copy of the GPS navigation message stored in a memory in the first GPS satellite;

or

comparing the waveform of the signal encoding the GPS navigation message with data representing the waveform stored in a memory in the first GPS satellite.

2. A method for verifying the integrity of a navigation message transmitted from a Global Positioning System (GPS) satellite, comprising:

monitoring the integrity of a GPS navigation message produced by a first GPS satellite, the monitoring performed by the first GPS satellite or a second GPS satellite; and

broadcasting a GPS integrity message from the first GPS satellite to GPS users in-view of the satellite, wherein the GPS integrity message indicates the integrity of the GPS navigation message produced by the first GPS satellite;

wherein the monitoring comprises;

transmitting the GPS navigation message to the second GPS satellite;

verifying the integrity of the GPS navigation message at the second GPS satellite; and

transmitting an integrity message from the second GPS satellite to the first GPS satellite indicating the integrity of the GPS navigation message.

3. A method for verifying the integrity of a navigation message transmitted from a Global Positioning System (GPS) satellite, comprising:

monitoring the integrity of a GPS navigation message produced by a first GPS satellite, the monitoring performed by the first GPS satellite or a second GPS satellite; and

broadcasting a GPS integrity message from the first GPS satellite to GPS users in-view of the satellite, wherein the GPS integrity message indicates the integrity of the GPS navigation message produced by the first GPS satellite;

wherein the monitoring comprises;

receiving at the first GPS satellite a signal from a beacon located at a fixed known location;

receiving at the first GPS satellite beacon position data from at least one other GPS satellite; and

verifying the integrity of satellite position data by comparing the satellite position data with the beacon position data and the fixed known location of the beacon.

4. A method for verifying the integrity of a navigation message transmitted from a Global Positioning System (GPS) satellite, comprising:

monitoring the integrity of a GPS navigation message produced by a first GPS satellite, the monitoring performed by the first GPS satellite or a second GPS satellite; and

broadcasting a GPS integrity message from the first GPS satellite to GPS users in-view of the satellite, wherein the GPS integrity message indicates the integrity of the GPS navigation message produced by the first GPS satellite;

wherein the GPS integrity message is transmitted on a channel separate from the channel on which the GPS navigation message is transmitted.

5. The method of claim 4, wherein the GPS integrity message is transmitted on an L5 channel.

6. A method for verifying the integrity of a navigation message transmitted from a Global Positioning System (GPS) satellite, comprising:

monitoring the integrity of a GPS navigation message produced by a first GPS satellite, the monitoring performed by the first GPS satellite or a second GPS satellite; and

broadcasting a GPS integrity message from the first GPS satellite to GPS users in-view of the satellite, wherein the GPS integrity message indicates the integrity of the GPS navigation message produced by the first GPS satellite;

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receiving the GPS integrity message at a GPS receiver;

decoding the GPS integrity message; and

relying on the GPS navigation message only if the GPS navigation message is determined to have integrity, as indicated by the GPS integrity message.

7. A method for verifying the integrity of a signal transmitted from a space vehicle, comprising:

monitoring the integrity of a transmission signal produced by a first space vehicle, the monitoring performed by the first pace vehicle or a second space vehicle; and

transmitting a first integrity signal from the first space vehicle to a user, wherein the first integrity signal indicates the integrity of the transmission signal produced by the first space vehicle;

wherein the monitoring comprises;

receiving the transmission signal at a receiver on the first space vehicle;

checking the integrity of the transmission signal by;

comparing the contents of a message encoded in the transmission signal with a copy of the message stored in a memory in the first space vehicle;

or

comparing the waveform of the transmission signal with data representing the waveform stored in a memory in the first space vehicle.

8. A method for verifying the integrity of a signal transmitted from a space vehicle, comprising:

monitoring the integrity of a transmission signal produced by a first space vehicle, the monitoring performed by the first space vehicle or a second space vehicle; and

transmitting a first integrity signal from the first space vehicle to a user, wherein the first integrity signal indicates the integrity of the transmission signal produced by the first space vehicle;

wherein the monitoring comprises;

transmitting the transmission signal to the second space vehicle;

verifying the integrity of the transmission signal at the second space vehicle; and

transmitting a second integrity signal from the second space vehicle to the first space vehicle indicating the integrity of the transmission signal.

9. A method for verifying the integrity of a signal transmitted from a space vehicle;

comprising;

monitoring the integrity of a transmission signal produced by a first space vehicle, the monitoring performed by the first space vehicle or a second space vehicle; and

transmitting a first integrity signal from the first space vehicle to a user, wherein the first integrity signal indicates the integrity of the transmission signal produced by the first space vehicle;

wherein the monitoring comprises;

receiving at the first space vehicle a signal from a beacon located at a fixed known location;

receiving at the first space vehicle beacon position data from at least one other space vehicle; and

verifying the integrity of satellite position data stored in the first space vehicle by comparing the satellite position data with the beacon position data and the fixed known location of the beacon.

10. A method for verifying the integrity of a signal transmitted from a space vehicle, comprising:

monitoring the integrity of a transmission signal produced by a first space vehicle, the monitoring performed by the first space vehicle or a second space vehicle; and

transmitting a first integrity signal from the first space vehicle to a user, wherein the first integrity signal indicates the integrity of the transmission signal produced by the first space vehicle;

wherein the first integrity signal is transmitted on a channel separate from the channel on which the transmission signal is transmitted.

11. The method of claim 10, wherein the first integrity signal is transmitted on an L5 channel.

12. The method of claim 11, further comprising:

receiving the transmission signal at a receiver;

decoding the transmission signal; and

relying on the transmission signal only if the transmission signal is determined to have integrity, as indicated by the first integrity signal.

13. The method for verifying the integrity of a navigation message transmitted from a Global Positioning System (GPS) satellite, comprising:

receiving at a first GPS satellite a signal from a beacon located at a fixed known location;

receiving at the first GPS satellite beacon position data from at least one other GPS satellite; and

verifying the integrity of satellite position data by comparing the satellite position data with the beacon position data and the fixed known location of the beacon.

14. The method for verifying the integrity of a signal transmitted from a space vehicle, comprising:

receiving at a first space vehicle a signal from a beacon located at a fixed known location;

receiving at a first space vehicle beacon position data from at least one other space vehicle; and

verifying the integrity of satellite position data stored in the first space vehicle by comparing the satellite position data with the beacon position data and the fixed known location of the beacon.

15. A system for verifying an integrity of a signal transmitted from a space vehicle, the system comprising:

a first space vehicle wherein the first space vehicle is configured to

produce a transmission signal;

monitor the integrity of the transmission signal; and

transmit a first integrity signal to a user, the first integrity signal indicative of the integrity of the transmission signal.

16. The system of claim 15, wherein the first space vehicle is a GPS satellite.

17. The system of claim 15, wherein the first space vehicle is further configured to receive the transmission signal at a receiver on the first space vehicle, and check the integrity of the transmission signal by associating a message encoded in the transmission signal with a copy of the message stored in a memory in the first space vehicle or by associating a waveform of the transmission signal with data representing the waveform stored in the memory in the first space vehicle.

18. The system of claim 15 further comprising a second space vehicle;

wherein

the first space vehicle is configured to transmit the transmission signal to the second space vehicle;

the second space vehicle is configured to verify the integrity of the transmission signal and transmit a second integrity signal to the first space vehicle indicative of the integrity of the transmission signal.

19. The system of claim 15, further comprising a beacon located at a fixed known location;

wherein the first space vehicle is configured to

receive a signal from the beacon;

receive beacon position data from at least a second space vehicle; and

verify the integrity of satellite position data stored in the first space vehicle by associating the satellite position data, the beacon position data, and the fixed known location of the beacon.

20. The system of claim 15, wherein the first space vehicle is configured to incorporate the first integrity signal as a message into the transmission signal.

21. The system of claim 15, wherein the first integrity signal is transmitted on a first channel separate from a second channel on which the transmission signal is transmitted.

22. The system of claim 21, wherein the first channel is an L5 channel.

23. The system of claim 15 further comprising a user receiving the transmission signal, decoding the transmission signal, and relying on the transmission signal only if the transmission signal is determined to have the integrity as indicated by the first integrity signal.

24. A system for verifying an integrity of a signal transmitted from a space vehicle, comprising:

a first space vehicle;

a second space vehicle;

wherein

the first space vehicle is configured to produce a transmission signal;

the second space vehicle is configured to monitor an integrity of the transmission signal; and

the first space vehicle is configured to transmit a first integrity signal to a user, the first integrity signal indicative of the integrity of the transmission signal.

25. The system of claim 24, wherein the first space vehicle and the second space vehicle are GPS satellites.

26. The system of claim 24, wherein the second space vehicle is configured to receive the transmission signal at a receiver on the second space vehicle and check the integrity of the transmission signal by associating a message encoded in the transmission signal with a copy of the message stored in a memory in the second space vehicle or by associating a waveform of the transmission signal with data representing the waveform stored in the memory in the second space vehicle.

27. The system of claim 24, wherein the first space vehicle is configured to transmit the transmission signal to the second space vehicle;

the second space vehicle is configured to verify the integrity of the transmission signal; and

the second space vehicle is configured to transmit a second integrity signal to the first space vehicle indicating the integrity of the transmission signal.

28. The system of claim 24, wherein the first space vehicle is configured to incorporate the first integrity signal as a message into the transmission signal.

29. The system of claim 24, wherein the first integrity signal is transmitted on a first channel separate from a second channel on which the transmission signal is transmitted.

30. The system of claim 29, wherein the first channel is an L5 channel.

31. The system of claim 24, further comprising a user wherein the user is configured to receive the transmission signal, decode the transmission signal, and rely on the transmission signal only if the transmission signal is determined to have the integrity as indicated by the first integrity signal.

32. The system for verifying an integrity of a signal transmitted from a space vehicle, comprising:

a first space vehicle;

a beacon located at a fixed known location;

wherein the first space vehicle is configured to

obtain the fixed known location of the beacon;

obtain beacon position data;

obtain satellite position data;

associate the satellite position data, the beacon position data and the fixed known location of the beacon;

verify the integrity of the satellite position data.

33. The system of claim 32, wherein the beacon position data includes a distance between the first space vehicle and the beacon.

34. The system of claim 32, wherein the beacon position data is received from a second space vehicle.

35. The system of claim 32, wherein the satellite position data is determined in response to ephemeris data received from 1 ground station.

36. The system of claim 32, wherein the satellite position data is determined in response to Autonav data received from a second space vehicle.

37. The system of claim 32, wherein the first space vehicle is a GPS satellite.

38. A system for verifying an integrity of a signal transmitted from a Global Positioning System (GPS) satellite, the system comprising:

a signal source configured to generate a GPS message;

a memory configured to store the generated GPS message;

an output system configured to transmit the produced GPS message;

a monitor antenna configured to receive the transmitted GPS message; and

a monitor processor configured to associate the stored GPS message and the received GPS message and produce an integrity message based on at least information associated with the stored GPS message and the receive GPS message.

39. The system of claim 38, wherein the signal source comprises a GPS processor.

40. The system of claim 38, wherein the signal source is free from a modulator configured to encode the GPS message into an RF carrier.

41. The system of claim 38, wherein the output system comprises a transmitter.

42. The system of claim 38, wherein the output system is free from a mission antenna.