Non-cooperative position, navigation, and timing extraction from VSAT communications signals using multi-beam phased array antenna
A ground antenna determines the current time and its own position from received signals that were transmitted by artificial earth satellites for communication. A high-gain multi-beam electrically-steered antenna is combined with a processing system to measure the angles between two or more satellites and determine the present distance to each satellite by the information broadcast on the TT&C channel. The knowledge of the angles and distances, as well as the trajectory of the satellites, can be combined with their locations as predicted by the satellite ephemeris data to triangulate the location of the receiver. This system is different from conventional GPS antennas because it does not require the cooperation of active communication with the satellites to derive a location estimate. The location is computed by the ground terminal, not by the satellite. This system can be used in cases where other locating services are offline, jammed, or otherwise unavailable to maintain location and time synchronization.
1. A satellite communication system, comprising:
a multi-beam antenna configured to receive different satellite transmissions from different directions simultaneously via different beams; and
one or more processors configured to:
direct the multi-beam antenna to track three or more non-global navigation satellite system (GNSS) satellites whose transmissions are signals lacking location and time data;
determine time based on one or more of the three or more non-GNSS satellites; and
determine a location of the satellite communication system based on location information determined from the signals from each of at least three of the three or more non-GNSS satellites.
2. The satellite communication system according to claim 1 , wherein the one or more processors is configured to determine an angle from the satellite communication system to each of the at least three of the three or more non-GNSS satellites as the location information.
3. The satellite communication system according to claim 2 , wherein the one or more processors is configured to determine the location of the satellite communication system based on the location information and triangulation.
4. The satellite communication system according to claim 1 , wherein the one or more processors is configured to determine a distance from the satellite communication system to each of the at least three of the three or more non-GNSS satellites as the location information.
5. The satellite communication system according to claim 4 , wherein the one or more processors is configured to determine the distance to the at least three of the three or more non-GNSS satellites based on the signals and on trajectory information for the at least three of the three or more non-GNSS satellites.
6. The satellite communication system according to claim 1 , wherein one or more of the one or more processors is configured to obtain ephemeris data indicating a provided trajectory for the one or more of the three or more non-GNSS satellites.
7. The satellite communication system according to claim 6 , wherein the one or more processors is configured to determine an estimated trajectory for the one or more of the three or more non-GNSS satellites based on a frequency shift in the signals from the one or more of the three or more non-GNSS satellites.
8. The satellite communication system according to claim 7 , wherein the one or more processors is configured to improve an estimate of the time and the location of the satellite communication system based on comparing the provided trajectory with the estimated trajectory for the one or more of the three or more non-GNSS satellites.
9. The satellite communication system according to claim 6 , wherein the ephemeris data is updated via communication with one of the three or more non-GNSS satellites.
10. The satellite communication system according to claim 9 , wherein the one of the three or more non-GNSS satellites is not one of the one or more of the three or more non-GNSS satellites used to obtain the time.
11. The satellite communication system according to claim 9 , wherein the ephemeris data is updated via terrestrial communication by the satellite communication system.
12. The satellite communication system according to claim 1 , wherein the satellite communication system is non-stationary, and the satellite communication system further comprises an inertial measurement unit (IMU) to locally track relative motion and position of the system.
13. The satellite communication system according to claim 12 , wherein one or more of the one or more processors is configured to integrate the relative motion and position of the satellite communication system obtained from the IMU into a determination of the location of the satellite communication system.
14. The satellite communication system according to claim 1 , wherein one or more of the one or more processors is configured to provide the location of the satellite communication system to a device that relies on but cannot obtain GNSS-based location.
15. A controller of a satellite communication system, comprising:
a memory configured to store orbital data for one or more non-global navigation satellite system (GNSS) satellites whose transmissions are signals lacking location and time data; and
a processor configured to:
command a multi-beam antenna to track three or more non-GNSS satellites;
determine time based on one or more of the three or more non-GNSS satellites; and
determine a location of the satellite communication system based on location information determined from the signals from each of at least three of the three or more non-GNSS satellites.
16. The controller according to claim 15 , wherein the processor is configured to determine an angle from the satellite communication system to each of the at least three or more non-GNSS satellites as the location information.
17. The controller according to claim 16 , wherein the processor is configured to determine the location of the satellite communication system based on the location information and triangulation.
18. The controller according to claim 15 , wherein the processor is configured to determine a distance from the satellite communication system to each of the at least three of the three or more non-GNSS satellites as the location information and to determine the distance to the at least three of the three or more non-GNSS satellites based on the signals and on trajectory information for the at least three of the three or more non-GNSS satellites.
19. The controller according to claim 15 , wherein the processor is further configured to obtain ephemeris data indicating a provided trajectory for the one or more of the three or more of the non-GNSS satellites.
20. The controller according to claim 19 , wherein the processor is configured to determine an estimated trajectory for the one or more of the three or more of the non-GNSS satellites based on a frequency shift in the signals from the one or more of the three or more of the non-GNSS satellites.
21. The controller according to claim 20 , wherein the processor is configured to improve an estimate of the time and the location of the satellite communication system based on comparing the provided trajectory with the estimated trajectory for the one or more of the three or more of the non-GNSS satellites.
22. The controller according to claim 19 , wherein the processor is configured to update the ephemeris data based on communication with one of the three or more of the non-GNSS satellites.