Phase step alert signal for GPS integrity monitoring

• US 7,095,369 B1
• Filed: 06/15/2004
• Issued: 08/22/2006
• Est. Priority Date: 06/15/2004
• 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): PHAN, DAO LINDA
• Application Number:
  US10/866,813
• Time in Patent Office: 798 Days
• Field of Search: 342/357.02, 342/357.05, 342/357.06, 342/372, 701/207, 701/213, 701/215
• US Class Current: 342/357.58
• CPC Class Codes: G01S 19/02 Details of the space or ground control segments
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment

Abstract

Alerting a user of an integrity error in a global positioning system (GPS) signal transmitted from a transmitter in a global positioning system (GPS) satellite, by detecting an error in the global positioning system (GPS) signal, alerting the user of the error by shifting a phase of the global positioning system (GPS) signal from an initial value by a predetermined phase-shift amount, and returning, in the case that the detected error is corrected, the phase of the global positioning system (GPS) signal to the initial value. Preferably, the GPS signal is phase-shifted by the predetermined phase-shift amount using an alert timing pattern which indicates the level of detected error.

Claims

1. A method for alerting a user of an integrity error in a global positioning system (GPS) signal transmitted from a transmitter in a global positioning system (GPS) satellite, the method comprising the steps of:

detecting an error in the global positioning system (GPS) signal;

alerting the user of the error by shifting a phase of the global positioning system (GPS) signal from an initial value by a predetermined phase-shift amount; and

returning, in the case that the detected error is corrected, the phase of the global positioning system (GPS) signal to the initial value.

2. A method according to claim 1, further including the step of quantifying an error amount for the error in the global positioning system (GPS) signal, wherein, in the alerting step, an alert timing pattern for shifting the phase by the predetermined phase-shift amount is set in accordance with the quantified error amount.

3. A method according to claim 1, further including the steps of:

correcting the error in the global positioning system (GPS) signal; and

confirming the correction to the user by shifting the phase of the global positioning system (GPS) signal by the predetermined phase-shift amount according to a confirmation timing pattern.

4. A method according to claim 1, wherein the predetermined phase-shift amount is 20 degrees and the initial value is 0 degrees.

5. A method according to claim 3, wherein, in the correcting step, the error is corrected in the global positioning system (GPS) satellite by transmitting the global positioning system (GPS) signal from a redundant transmitter.

6. A method according to claim 3, wherein, in the correcting step, the error is corrected in the global positioning system (GPS) satellite by reloading a set of ephemeris data.

7. A method according to claim 3, wherein, in the correcting step, the error is corrected in the global positioning system (GPS) satellite by using a redundant atomic clock.

8. A method according to claim 1, wherein, in the detecting step, the error in the global positioning system (GPS) signal is detected by a monitoring the global positioning system (GPS) signal with a monitoring receiver mounted on the global positioning system (GPS) satellite.

9. A method according to claim 1, wherein, in the detecting step, the error in the global positioning system (GPS) signal is detected by receiving the global positioning system (GPS) signal at a ground station having a known location, determining a calculated location based on the received global positioning system (GPS) signal, comparing the calculated location with the known location to determine the error, and sending a correction message containing the error from the ground station to the global positioning system (GPS) satellite.

10. A method according to claim 2, wherein the alert timing pattern is comprised of a plurality of cycles, wherein, in each cycle, the phase is shifted from the initial value by the predetermined phase-shift amount for a predetermined time and then returned to the initial value for the predetermined time.

11. A method according to claim 10, wherein the predetermined time is equal to or greater than 10 milliseconds.

12. A method according to claim 3, wherein the confirmation timing pattern is comprised of a plurality of cycles, wherein, in each cycle, the phase is shifted from the initial value by the predetermined phase-shift amount for a predetermined time and then returned to the initial value for the predetermined time.

13. A method according to claim 12, wherein the predetermined time is equal to 10 milliseconds.

15. A computing apparatus provided in a global positioning system (GPS) satellite, the computing apparatus comprising:

a processor; and

a memory which stores computer-executable process steps to alert a user of an integrity error in a global positioning system (GPS) signal transmitted from a transmitter in the global positioning system (GPS) satellite, the computer-executable process steps including steps to perform a method according to any of claims 1 to 14.

14. A method for alerting a user of an integrity error in a global positioning system (GPS) signal transmitted from a transmitter in a global positioning system (GPS) satellite, the method comprising the steps of:

detecting an error in the global positioning system (GPS) signal;

quantifying an error amount for the error in the global positioning system (GPS) signal;

setting an alert timing pattern for shifting the phase by a predetermined phase-shift amount in accordance with the quantified error amount;

alerting the user of the error by shifting a phase of the global positioning system (GPS) signal from an initial value by the predetermined phase-shift amount in accordance with the alert timing pattern;

correcting the error in the global positioning system (GPS) signal;

confirming the correction to the user by shifting the phase of the global positioning system (GPS) signal by the predetermined phase-shift amount in accordance with a confirmation timing pattern; and

returning the phase of the global positioning system (GPS) signal to the initial value.

16. A computing apparatus provided in a global positioning system (GPS) satellite for alerting a user of an integrity error in a global positioning system (GPS) signal transmitted from a transmitter in the global positioning system (GPS) satellite, the computing apparatus comprising:

detecting means for detecting an error in the global positioning system (GPS) signal;

alerting means for alerting the user of the error by shifting a phase of the global positioning system (GPS) signal from an initial value by a predetermined phase-shift amount; and

returning means for returning, in the case that the detected error is corrected, the phase of the global positioning system (GPS) signal to the initial value.