Scanned acquisition using pre-track data

• US 20040165892A1
• Filed: 02/21/2003
• Published: 08/26/2004
• Est. Priority Date: 02/21/2003
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Inventors: Mendenhall, Todd L.
• Granted Patent: US 7,995,926 B2
• Time in Patent Office: Days
• US Class Current: 398/118
• CPC Class Codes: G01S 17/74 Systems using reradiation of electromagnetic waves other than radio waves, e.g. IFF, i.e. identification of friend or foe
• CPC Class Codes: G01S 3/789 using rotating or oscillating beam systems, e.g. using mirrors, prisms

Abstract

A scan acquisition technique for acquiring terminals (62, 64) that does not rely on precise alignment between a sensor (66, 70) and a transmitter (68, 72) associated with the terminals (62, 64). The terminals (62, 64) separate uncertainty regions (76, 78) into a plurality of sections (88, 90). Scan beams (82, 84) include encoded information of what section (88, 90) the scan beam (82, 84) is currently scanning. Each terminal (62, 64) will eventually receive the scan beam (82, 84) of the other terminal (62, 64). When it does, it will encode its scan beam (82, 84) with both the outgoing code and the return code for that section (88, 90), so that when it'"'"'s scan beam (82, 84) is received by the other terminal (62, 64), that terminal (62, 64) will know what scan section (88, 90) the other terminal (62, 64) is located.

Claims

1. A method of acquiring alignment between a first terminal and second terminal, said method comprising:

identifying a first uncertainty region that the first terminal is positioned within;

identifying a second uncertainty region that the second terminal is positioned within;

separating the first uncertainty region and the second uncertainty region into a plurality of contiguous scan sections where each scan section is identified by a section code;

transmitting a first scan beam from the first terminal that sequentially scans through the scan sections in the second uncertainty region, said first scan beam being encoded with both an outgoing section code for the particular scan section in the second uncertainty region that the first scan beam is scanning and a return section code that identifies the section decoded from the second scan beam if the first terminal was hit;

transmitting a second scan beam from the second terminal that sequentially scans through the scan sections in the first uncertainty region, said second scan beam being encoded with both an outgoing section code for the particular scan section in the first uncertainty region that the second scan beam is scanning and a return section code that identifies the section decoded from the first scan beam if the second terminal was hit;

receiving the first scan beam by the second terminal when the first scan beam illuminates the section of the second uncertainty region that the second terminal is located;

encoding the second scan beam with the section code from the first scan beam received by the second terminal; and

receiving the second scan beam by the first terminal when the second scan beam scans the section of the first uncertainty region that the first terminal is located where the second scan beam includes the section code for the second terminal so that the first terminal knows the location of the second terminal in the second uncertainty region.

2. The method according to claim 1 further comprising encoding the first scan beam with the section code from the second scan beam received by the first terminal, and receiving the first scan beam by the second terminal when the first scan beam scans the scan section of the second uncertainty region that the second terminal is located where the first scan beam includes the section code for the first terminal so that the second terminal knows the location of the first terminal in the first uncertainty region.

3. The method according to claim 2 further comprising separating the scan section in the first uncertainty region that the first terminal is located into a plurality of scan sections, and separating the scan, section in the second uncertainty region that the second terminal is located into a plurality of scan sections.

4. The method according to claim 3 further comprising repeatedly separating the scan section in the first uncertainty region that the first terminal is located into a plurality of scan sections and separating the scan section in the second uncertain region that the second terminal is located into a plurality of scan sections until the size of the first and second uncertainty regions is about one-half of the beamwidth of the first and second scan beams.

5. The method according to claim 4 wherein the first and second scan beams have a beamwidth of 1-20 microradians.

6. The method according to claim 1 wherein separating the first uncertainty region and the second uncertainty region into a plurality of contiguous scan sections includes separating the first uncertainty region and the second uncertainty region into 1024 contiguous scan sections.

7. The method according to claim 1 wherein transmitting the first and second scan beams include scanning the first and second scan beams in two-dimensions.

8. The method according to claim 1 wherein the first scan beam and the second scan beam are optical beams.

9. A method of providing optical alignment between a first terminal and a second terminal so that the first and second terminals can transmit optical data beams to each other, said method comprising transmitting scan beams from the first and second terminals to the other first or second terminal, encoding the scan beams with a section code identifying a scan section that the scan beam is currently scanning, receiving the encoded scan beam by the first or second terminal, encoding the transmitted scan beam with the section code from the received scan beam, and receiving the transmitted scan beam by the first or second terminal to identify the position of the first and second terminals.

10. The method according to claim 9 further comprising separating the scan section that the first terminal is located into a plurality of scan sections, and separating the scan section that the second terminal is located into a plurality of scan sections after the position of the first and second terminals is determined.

11. The method according to claim 10 further comprising repeatedly separating the scan section that the first terminal is located into a plurality of scan sections and separating the scan section that the second terminal is located into a plurality of scan sections until the size of the scan section is about one-half of the beamwidth of the scan beams.

12. The method according to claim 11 wherein the scan beams have a beamwidth of 1-20 microradians.

13. The method according to claim 9 wherein transmitting the scan beams includes transmitting the scan beams in two-dimensions.

14. A communications system comprising:

a first terminal including a first sensor and a first transmitter, said first terminal being positioned within a first uncertainty region, said first uncertainty region being separated into a plurality of contiguous scan sections where each scan section in the first uncertainty region is identified by a scan code; and

a second terminal including a second sensor and a second transmitter, said second terminal being positioned within a second uncertainty region, said second uncertainty region being separated into a plurality of contiguous scan sections where each scan section in the second uncertainty region is identified by a scan code, said first transmitter transmitting a first scan beam for scanning the second uncertainty region and being encoded with the scan code of the scan section in the second uncertainty region it is currently scanning and said second transmitter transmitting a second scan beam for scanning the first uncertainty region and being encoded with the scan code of the scan section it is currently scanning, said first scan beam also being encoded with the scan code from the second scan beam when the first sensor receives the second scan beam and said second scan beam also being encoded with the scan code from the first scan beam when the second sensor receives the first scan beam so that the first terminal knows the location of the second terminal in the second uncertainty region and the second terminal knows the location of the first terminal in the first uncertainty region.

15. The system according to claim 14 wherein the first scan beam and the second scan beam are optical beams and the first sensor and the second sensor include optical telescopes for receiving the optical scan beams.

16. The system according to claim 14 wherein the first sensor and the second sensor include InGaAs sensor cells.

17. The system according to claim 14 wherein the first transmitter and the second transmitter scan the first scan beam and the second scan beam in two-dimensions in the first and second uncertainty regions.

18. The system according to claim 14 wherein the first and second scan beams have a beam width of about 1-20 microradians.