System for accurately monitoring aircraft position during training exercises

• US 5,144,315 A
• Filed: 12/10/1990
• Issued: 09/01/1992
• Est. Priority Date: 02/10/1989
• Status: Expired due to Term

• Current Assignee: Cardion Newco Incorporated
• Original Assignee: Cardion, Inc.
• Inventors: Schwab, Carl E., Goodrich, Fred N. S.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US07/625,040
• Time in Patent Office: 631 Days
• Field of Search: 342/30, 342/36, 342/37, 342/43, 342/45, 342/46, 342/49, 342/59, 342/169, 342/399, 342/444, 342/453, 342/454, 342/463, 342/465
• US Class Current: 342/49
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 13/78 discriminating between different kinds of targets, e.g. IFF-radar, i.e. identification of friend or foe G01S13/75, G01S13/79 take precedence
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence

Abstract

Tracking system for monitoring aircraft position during simulated training exercises. Standard IFF transponders on the aircraft are periodically enabled by a squitter transmitter mounted on the aircraft. On the ground a plurality of receiving stations are interconnected through a communication link. The transponder replies are received at each receiving station. The time of arrival for each of the transponder replies is measured and communicated to one of the receiving stations. Using Loran techniques, accurate longitudinal and latitude coordinates are determined from the time of arrival data.

Claims

1. A system for tracking an aircraft, equipped with an IFF transponder which emits a signal containing a data signal identifying the aircraft altitude during training exercises, comprising:

a squitter transmitter mounted on said aircraft for interrogating said transponder whereby said data signal is transmitted;

a plurality of ground receiving stations spaced apart over a test range;

a communication link connecting said receiving stations; and

,

means at one of said receiving stations for receiving information from said other receiving stations over said communication link identifying the time of arrival of said transmitted data signal to each receiving station, and calculating from said time of arrivals the position of said aircraft.

2. The system for tracking aircraft of claim 1 wherein said means at said one receiving station calculates air speed and heading of said aircraft.

3. The system of claim 1 further including a plurality of spaced apart simulated ground radar signals against which said aircraft can conduct evasive maneuvers.

4. The system of claim 1 wherein said means at said one station is a digital computer.

5. The system for tracking of claim 1 wherein said communication link is two way between said one receiving station and said remaining receiving stations.

6. The system for tracking of claim 5 wherein said one receiving station distributes real time clock synchronization data over said communication link to said remaining receiving stations.

7. The system for tracking according to claim 1 further comprising a disabling switch coupled to said aircraft landing gear for disabling transmissions from said transponder when said aircraft is one the ground.

8. The system of claim 1 wherein said squitter transmitter is mounted to a weapon support on said aircraft.

9. The system of claim 1 wherein said squitter transmitter is enabled in response to a TACAN interrogation generator on said aircraft.

10. The system of claim 1 further comprising:

a test transponder located at a known distance from each ground receiving station; and

,

means for triggering said test transponder into a transmission mode, whereby time of arrival information is received by said receiving stations and transmitted to said one receiving station for determining errors in time of arrival determinations made at each receiving station.

11. The system of claim 10 wherein said triggering means enables said test transponder at a rate of one transmission per second.

21. The system of claim 1 further comprising an accelerometer connected to said squitter transmitter for varying the rate of interrogation of said transmitter.

12. A system for tracking aircraft equipped with an IFF transponder and TACAN interrogation equipment during a training exercise comprising:

a squitter transmitter supported on said aircraft for interrogating said IFF transponder;

a circuit for enabling said squitter transmitter in response to each TACAN interrogation pulse produced by said TACAN interrogation equipment;

a plurality of ground receiving stations positioned about a training site, said ground receiving stations including a receiver for receiving each TACAN interrogation pulse and IFF transponder reply, and correlating said TACAN pulse, IFF reply and aircraft identity, each receiving station measuring the time of arrival of said transponder replies, one of said plurality of ground receiving stations serving as a central station;

a digital data link connecting said central ground receiving station to the remaining ground receiving stations, said data link transferring time of arrival information from said remaining receiving stations to said central station; and

a central computer at said central station for receiving said time of arrival information, and calculating from said time of arrival information longitudinal and latitude position coordinates for said aircraft.

13. A system for tracking aircraft according to claim 12 comprising a message assembler at said remaining receiving stations for compiling a message including a measured time of arrival and a decoded altitude signal, said message assembler connected to transmit said message over said digital data link to said one station.

14. A system for tracking aircraft according to claim 13 wherein said circuit for enabling said squitter transmitter is responsive to a single TACAN pulse frequency assigned to said aircraft.

15. A system for tracking aircraft according to claim 14 wherein each ground station receiver is capable of receiving a plurality of TACAN pulse frequencies, and identifies each aircraft by a received TACAN pulse frequency.

16. A system for tracking aircraft according to claim 12 further comprising a landing gear operated switch for disabling said squitter transmitter when said aircraft is on the ground.

17. A system for tracking an aircraft, equipped with a transponder which initiates a standard replay unique to said aircraft in response to a radio frequency interrogation signal comprising:

means located on said aircraft for selectively interrogating said transponder at intervals which varies about a nominal rate, whereby said standard reply unique to said aircraft is continuously transmitted;

a plurality of ground receiving stations spaced apart over a test range for monitoring the performance of said aircraft, said ground receiving stations measuring the time of arrival of said replay to derive position information for said aircraft, as well as decoding said standard replay obtaining data unique to said aircraft;

a communication link interconnecting said plurality of ground receiving stations for transmitting said time of arrival information and decoded replay data from said ground receiving stations to a central computer; and

,

a central computer for receiving said time of arrival information and replay data, and for computing said position information, and identifying said aircraft with said position information, tracking said aircraft as it enters an area defined by said ground receiving stations.

18. The system of claim 17 wherein said means for interrogating is a transmitter on said aircraft which produces a radio frequency signal for interrogating said transponder.

19. The system of claim 18 wherein said squitter transmitter produces a signal for interrogating said transponder in multiple modes.

20. The systems of claim 19, wherein one of said modes produces a reply from said transponder indicating the identity of said aircraft.

24. The system of claim 17 further comprising means for generating a signal for varying said transponder interrogation rate in accordance with changes in said aircraft performance.

25. The system of claim 24 further comprising means for decoding at one of said ground receiving stations the average periodic rate at which said standard replies are received.

22. The system of claim further comprising means for generating a signal for varying the rate of interrogation of said squitter transmitter.

23. The system of claim 22 wherein said means for generating a signal produces a signal related to said aircraft performance.