Autonomous geolocation and message communication system and method

• US 6,147,644 A
• Filed: 12/30/1996
• Issued: 11/14/2000
• Est. Priority Date: 12/30/1996
• Status: Expired due to Fees

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Castles, Milford Pike, Moryl, James Andrew, Boyd, Austin Walker Jr.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US08/774,604
• Time in Patent Office: 1,415 Days
• Field of Search: 342/357, 342/357.1, 342/367, 342/357.09, 342/357.07, 455/427, 455/428, 455/440, 455/456
• US Class Current: 342/367
• CPC Class Codes: H04B 7/18547 for geolocalisation of a station position fixing by direction or distance determination G01S5/00

Abstract

A system and method for transmitting information to a receiving station via one or more Low Earth Orbit (LEO) satellites includes a device which is capable of operating autonomously to transmit signals to a selected LEO satellite for relay to a receiving station identifying the device and its geolocation including longitude and latitude and/or speed, altitude and heading or course. The device includes a microprocessor which operates a Global Positioning System (GPS) receiver for receiving GPS signals to identify its geolocation and precise time. A nonvolatile memory onboard the device stores LEO satellite ephemeris data, and identification, operational and message formatting information to enable the device to transmit information including voice, data and/or the geolocation of the device to a selected LEO satellite, such as the next visible LEO satellite, for relay to a receiving station. The device may be operated to select the next visible LEO satellite for transmission of information when the satellite is visible and the device is within the LEO satellite visibility range or footprint. Alternatively, the device may select one or more LEO satellites for transmission at selected times and may store information, including geolocation data, when a selected LEO satellite is visible.

Claims

1. A method for communicating geolocation and messages from a device to a receiving station, comprising the steps of:

a) receiving signals by the device from a position determining system;

b) determining a geolocation of the device from the received position determining signals;

c) determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station by using a current time, the device geolocation, the receiving station geolocation, and low earth orbit satellite ephemeris data stored in the device; and

d) transmitting the geolocation and messages from the device to the low earth orbit satellite during the visibility time duration when the low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station by the low earth orbit satellite.

2. A method according to claim 1, wherein the position determining system is the NAVSTAR/Global Positioning System.

3. A method according to claim 1, wherein the step of determining a geolocation comprises the steps of autonomously determining a longitude value and a latitude value of a position of the device and simultaneously and autonomously determining a time value taken at that position of the device.

4. A method according to claim 1, wherein the step of determining a geolocation comprises the steps of autonomously determining a three-dimensional value of a position of the device and simultaneously and autonomously determining a time value taken at that position of the device.

5. A method according to claim 1 further comprising the steps of:

a) determining a speed value and a heading value of the device from the position determining system; and

b) transmitting the speed value and the heading value from the device to the low earth orbit satellite during the visibility time duration when the low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station by the low earth orbit satellite.

6. A method according to claim 1, wherein the step of determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station, and the step of transmitting the geolocation comprise the steps of:

a) determining a visibility time duration when each of a plurality of low earth orbit satellites is visible to both the device and the receiving station;

b) selecting a low earth orbit satellite having a selected visibility time duration from the plurality of low earth orbit satellites; and

c) transmitting the geolocation and messages from the device to the selected low earth orbit satellite during the selected visibility time duration when the selected low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station by the low earth orbit satellite.

7. A method according to claim 6, wherein the step of selecting a low earth orbit satellite comprises the steps of:

a) comparing the visibility time duration for each of the plurality of low earth orbit satellites; and

b) selecting a low earth orbit satellite having a selected visibility time duration and a shortest time interval between a present time and a beginning time of the selected visibility time duration.

8. A method according to claim 6, wherein the step of determining a visibility time duration when each of a plurality of low earth orbit satellites is visible to both the device and the receiving station, comprises the step of determining a time duration for each of a plurality of earth orbit satellites when:

a) an elevation angle of a low earth orbit satellite is greater than a mask angle based on a predicted position of the device; and

b) a visibility footprint of the low earth orbit satellite indicates a visibility time duration when both the device and the receiving station are contained within the visibility footprint.

9. A method according to claim 1, wherein the step of determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station, and the step of transmitting the geolocation comprise the steps of:

a) determining a visibility time duration when each of a plurality of low earth orbit satellites is visible to both the device and the receiving station;

b) selecting more than one low earth orbit satellite having selected visibility time durations from the plurality of low earth orbit satellites; and

c) transmitting the geolocation and messages from the device to the selected low earth orbit satellites during the selected visibility time durations when the low earth orbit satellites are visible to both the device and the receiving station, for relay to the receiving station by the low earth orbit satellite.

10. A method according to claim 1, wherein the step of determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station, and the step of transmitting the geolocation comprise the steps of:

a) determining a maximum elevation angle and an azimuth for each of a plurality of low earth orbit satellites based on the device geolocation and satellite ephemeris data stored in the device;

b) comparing the maximum elevation angle with a device mask angle for each satellite;

c) identifying each satellite having a maximum elevation angle that exceeds the device mask angle;

d) selecting identified satellites having a maximum elevation angle that exceeds the mask angle and having a visibility footprint that provides visibility to both the device and the receiving station;

e) determining a selected visibility time duration for each selected satellite when the maximum elevation angle exceeds the mask angle and when the satellite visibility footprint provides visibility to both the device and receiving station; and

f) transmitting the geolocation and messages from the device to a predetermined number of the selected low earth orbit satellites during the selected visibility time duration for each of the predetermined number of selected low earth orbit satellites.

11. A method according to claim 10, wherein the step of transmitting the geolocation comprises transmitting the geolocation and messages from the device to a predetermined number of the selected low earth orbit satellites when each of the predetermined number of selected low earth orbit satellites is at its maximum elevation angle.

12. A method according to claim 10, wherein the step of selecting identified satellites further comprises selecting identified satellites having a shortest time interval between a present time and a beginning time of an identified satellite selected visibility time duration.

13. A method according to claim 10, wherein the step of transmitting the geolocation comprises the steps of:

a) steering an antenna connected to the device to a maximum elevation angle and an azimuth for a selected low earth orbit satellite; and

b) transmitting the geolocation and messages from the device to the selected low earth orbit satellite during the selected satellite selected visibility time.

14. A method according to claim 1, wherein the step of transmitting the geolocation comprises transmitting the geolocation and messages more than once from the device to the low earth orbit satellite when the low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station by the low earth orbit satellite.

15. A method according to claim 1, wherein the step of transmitting the geolocation comprises transmitting the geolocation and messages at least once during a first half of the visibility time duration, and at least once during a second half of the visibility time duration.

16. A method according to claim 1, wherein the step of receiving signals by the device comprises:

a) receiving signals by a receiver in the device from a position determining system at a set of predetermined times; and

b) reducing power to the receiver at times between the set of predetermined times.

17. A method according to claim 1, wherein the step of transmitting the geolocation comprises:

a) selecting a transmitter power level;

b) transmitting the geolocation and messages by a transmitter in the device to the low earth orbit satellite during the visibility time duration when the low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station; and

c) reducing the transmitter power level at times the transmitter is not transmitting the geolocation and messages.

18. A method according to claim 1, further comprising the step of preprogramming the device with operational parameters.

19. A method according to claim 18, wherein the operational parameters comprise ephemeris data, operating area information, identity codes, and transmission data formats for a plurality of low earth orbit satellites.

20. A method according to claim 18, wherein the preprogramming step is performed by downloading the operational parameters to the device from a computer connected to a connector positioned on the device.

21. A method according to claim 1, wherein the step of transmitting the geolocation data further comprises selecting a data rate, modulation format, data format, transmission frequency and signal transmission power level for compatibility with a selected constellation low earth orbit satellites.

22. A method according to claim 1, wherein the step of receiving signals from a position determining system is performed by a receive antenna and the step of transmitting the geolocation is performed by a transmit antenna.

23. A method according to claim 1, wherein the step of receiving signals from a position determining system comprises receiving signals from at least three earth orbit position determining satellites.

24. A method according to claim 1, wherein the receiving station comprises more than one receiving station.

25. A method according to claim 1, wherein the messages includes voice and data information.

26. A device for communicating geolocation and messages to a receiving station, comprising:

a) means for receiving signals by the device from a position determining system;

b) means for determining a geolocation of the device from the received position determining signals;

c) means for determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station by using a current time, the device geolocation, the receiving station geolocation, and low earth orbit satellite ephemeris data stored in the device; and

d) means for transmitting the geolocation and messages from the device to the low earth orbit satellite during the visibility time duration when the low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station by the low earth orbit satellite.

27. A device according to claim 26, wherein the position determining system is the NAVSTAR/Global Positioning System.

28. A device according to claim 26, wherein the receiving station includes a means for displaying a track depicting the geographical movement of the device.

29. A device according to claim 26, wherein the means for receiving signals from a position determining system comprises an omnidirectional receive antenna connected to a geolocation data and time signal receiver.

30. A device according to claim 29, further comprising a power management means for reducing power to the geolocation data and time receiver at times the receiver is not receiving.

31. A device according to claim 26, wherein the means for determining a geolocation from the received position determining signals comprises:

a) a microprocessor connected to a geolocation data and time signal receiver;

b) a real time clock connected to the microprocessor;

c) a nonvolatile memory connected to the microprocessor for storing control program software for computing geolocation; and

d) a computer program stored in the nonvolatile memory for controlling the microprocessor to compute a geolocation.

32. A device according to claim 31, wherein the computer program controls the microprocessor for autonomously computing a longitude value, a latitude value and a time value of the position of the device.

33. A device according to claim 31, wherein the computer program controls the microprocessor for computing a speed value and a heading value of the device motion.

34. A device according to claim 26, wherein the means for determining a visibility time duration comprises:

a) a microprocessor;

b) a nonvolatile memory connected to the microprocessor for storing control program software, low earth orbit satellite ephemeris data and operating area information;

c) a geolocation stored in memory; and

d) a computer program stored in nonvolatile memory for controlling the microprocessor to compute a visibility time duration.

35. A device according to claim 34, wherein the computer program controls the microprocessor for computing the visibility time duration using a present time, the device geolocation, a receiving station geolocation, and low earth orbit ephemeris data stored in nonvolatile memory.

36. A device according to claim 34, wherein the computer program controls the microprocessor for determining a visibility time duration when an elevation angle of a low earth orbit satellite is greater than a mask angle and a visibility footprint of the low earth orbit satellite contains both the device and the receiving station.

37. A device according to claim 26, wherein the means for transmitting the geolocation comprises:

a) a satellite transmitter connected to a microprocessor; and

b) a transmit antenna connected to the satellite transmitter.

38. A device according to claim 37, further comprising an antenna steering means connected to the microprocessor and the transmit antenna for steering the transmit antenna to an azimuth angle and an elevation angle.

39. A device according to claim 37, wherein the transmit antenna is an omni-directional antenna.

40. A device according to claim 37, further comprising a power management means for reducing power to the satellite transmitter at times the transmitter is not transmitting.

41. A device according to claim 37, further comprising a means for controlling a data rate, modulation format, data format, transmission frequency and signal transmission power level of the satellite transmitter by the microprocessor.

42. A device according to claim 26, further comprising a message display unit, a power source and an input/output connector.

43. A device according to claim 26, further comprising a means for preprogramming the device by downloading operational parameters to the device from a computer connected to a connector positioned on the device.

44. A system for communicating geolocation and messages from a device to a receiving station, comprising:

a) a position determining system for transmitting position determining signals;

b) a device for;

1) receiving the position determining signals;

2) determining geolocation of the device;

3) determining a visibility time duration when a low earth orbit satellite is visible to both the device and a receiving station by using a current time, the device geolocation the receiving station geolocation, and low earth orbit satellite ephemeris data stored in the device; and

4) transmitting the geolocation and messages from the device to a low earth orbit satellite during the visibility time duration;

c) a low earth orbit satellite for receiving the geolocation and messages from the device and transmitting such information to a receiving station; and

d) a receiving station for receiving the geolocation and messages, processing such information, and displaying such information.

45. A system according to claim 44, wherein the position determining system is the NAVSTAR/Global Positioning System.

46. A system according to claim 44, wherein determining geolocation comprises determining a longitude value, a latitude value, and an associated time value of the device.

47. A system according to claim 46, further comprising determining a speed value and a heading value of the device.

48. A system according to claim 44, wherein determining geolocation comprises determining a three-dimensional value of the position and an associated time value of the device.

49. A system according to claim 44, wherein determining a visibility time duration is based on low earth orbit satellite ephemeris data, mask angles, maximum elevation angle and associated azimuth, satellite visibility footprint, and receiving station location.

50. A system according to claim 44, wherein the low earth orbit satellite comprises a receiver and a transmitter for relaying geolocation and messages from the device to the receiving station.

51. A microprocessor-implemented computer program for communicating geolocation and messages from a device to a receiving station, comprising the steps of:

a) receiving signals by the device from a position determining system by controlling a geolocation data and time signal receiver;

b) determining a current geolocation of the device from the received position determining signals;

c) determining a visibility time duration when a low earth orbit satellite is visible to both the device and the receiving station by using a current time, the device geolocation, the receiving station geolocation and low earth orbit satellite ephemeris data stored in the device; and

d) transmitting the geolocation and messages from the device to the low earth orbit satellite during the visibility time duration when the low earth orbit satellite is visible to both the device and the receiving station, for relay to the receiving station, by controlling transmission of a device satellite transmitter.

52. A microprocessor-implemented computer program according to claim 51, wherein the step of receiving signals by the device by controlling a geolocation data and time signal receiver comprises the steps of:

a) applying power to the receiver;

b) activating the receiver for receiving position determining signals;

c) acquiring position determining signals;

d) storing the position determining signals in a memory; and

e) reducing power to the receiver.

53. A microprocessor-implemented computer program according to claim 51, wherein the step of determining a geolocation of the device comprises the steps of:

a) accessing the position determining signals from the memory;

b) computing a geolocation from the position determining signals comprising a longitude value, a latitude value, and a time value; and

c) storing the geolocation in the memory.

54. A microprocessor-implemented computer program according to claim 51, wherein the step of determining a visibility time duration comprises the steps of:

a) computing a maximum elevation angle and an associated azimuth for each of a plurality of low earth orbit satellites based on the device geolocation and satellite ephemeris data stored in memory;

b) comparing the maximum elevation angle with a device mask angle for each satellite;

c) identifying each satellite having a maximum elevation angle that exceeds the device mask angle;

d) selecting identified satellites having a maximum elevation angle that exceeds the mask angle and having a visibility footprint that provides visibility to both the device and the receiving station; and

e) determining a selected visibility time duration for a selected satellite having a maximum elevation angle that exceeds the mask angle when the visibility footprint of the selected satellite provides visibility to both the device and the receiving station.

55. A microprocessor-implemented computer program according to claim 51, wherein the step of transmitting the geolocation and messages from the device to the low earth orbit satellite by controlling transmission of a device satellite transmitter comprises the steps of:

a) applying power to the device satellite transmitter;

b) setting transmission parameters of the device satellite transmitter comprising data rate, modulation format, data format, transmission frequency, and signal transmission power level;

c) transmitting the geolocation and messages from the device satellite transmitter to the low earth orbit satellite during the visibility time; and

d) reducing power to the device satellite transmitter.

56. Computer readable medium containing instructions for performing the steps in the computer program as recited in claim 51.