Method and system for two-dimensional interferometric radiometry

• US 6,441,376 B1
• Filed: 12/06/2000
• Issued: 08/27/2002
• Est. Priority Date: 12/07/1999
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Glass, Carter M., Alexander, Scott David, Golubiewski, Arthur Casimir, Harrison, Lori K., Herring, Christopher Taylor
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Gagliardi, Albert
• Application Number:
  US09/731,113
• Publication Number:
  US 20020074497A1
• Time in Patent Office: 629 Days
• Field of Search: 250/342, 250/332, 342/25, 342/424
• US Class Current: 250/342
• CPC Class Codes: G01C 11/00 Photogrammetry or videogrammetry, e.g. stereogrammetry; Photographic surveying

Abstract

A method and system are disclosed for imaging a planetary surface region of interest (ROI). In a primary application, a plurality of space vehicles having antennas mounted thereupon are utilized to collect thermal radiation emitted from the ROI and generate corresponding thermal emission signals. Such thermal emission signals may be combined to yield one or more simple interferometric fringes. The simple fringes may be employed to yield a pixel image of the ROI. In one aspect, one or more simple interferometric fringes may be utilized to generate one or more compound interferometric fringes for use in formation of the pixel image. One or more compound fringes may be utilized to generate additional levels of compound fringes for use in formation of the pixel image. In another aspect, the space vehicles may be positioned in a “near-field” imaging arrangement relative to the ROI and a matched filtering approach may be utilized for extracting amplitude data from the interferometric fringe(s) on a basis for use in pixel image formation.

Claims

1. A method for obtaining a pixel image of a planetary surface region of interest, comprising:

collecting thermal radiation emissions from a planetary surface region of interest (ROI) by a plurality of spaced antennas to obtain a corresponding plurality of thermal emission signals;

first combining a first thermal emission signal with a complex conjugate of a second thermal emission signal to obtain a first simple interferometric fringe signal; and

,

second combining said first simple interferometric fringe signal with another signal for said ROI to obtain a first compound interferometric fringe signal employable in the formation of a pixel image of the ROI.

2. A method as recited in claim 1, wherein:

said first combining step further includes combining one of said first and second thermal emission signals with a complex conjugate of a third thermal emission signal to obtain a second simple interferometric fringe signal; and

,

said another signal is one of (i) said second simple interferometric fringe signal, and (ii) one of said first, second and third thermal emission signals.

3. A method as recited in claim 2, wherein:

said first combining step further includes combining said second thermal emission signal with said complex conjugate of said third thermal emission signal to obtain a third simple interferometric fringe signal; and

,

said second combining step further includes combining said second simple interferometric fringe signal with one of (i) said third simple interferometric fringe signal, and (ii) one of said first, second and third thermal emission signals, to obtain a second compound interferometric fringe signal employable in the formation of said pixel image of the ROI.

4. A method as recited in claim 1, further including:

extracting at least one pixel value for each of a plurality of pixel locations from said first compound interferometric fringe signal for use in formation of said pixel image of the ROI.

5. A method as recited in claim 4, wherein center imaging axes for at least two of said plurality of spaced antennas define an angle of at least about 2°

therebetween, and wherein said plurality of antennas collect said thermal radiation emissions over a bandwidth of about 1 MHz to 1 GHz.

6. A method as recited in claim 5, wherein the method further includes:

combining said at least one amplitude component corresponding with each given one of said plurality of pixel locations for said first compound interferometric image signal to obtain a first interferometric image signal employable in the formation of said pixel image of the ROI.

7. A method as recited in claim 4, wherein said extracting step includes:

applying a different matched filter in corresponding relation to each of said plurality of pixel locations for said first compound interferometric image signal to obtain at least one amplitude component corresponding with each of said pixel locations for use in formation of said pixel image of the ROI.

8. A method as recited in claim 1, wherein the method further includes:

filtering said first simple interferometric fringe signal to obtain the first simple interferometric fringe signal prior to said second combining step.

9. A method as recited in claim 1, wherein the method further includes:

utilizing said plurality of thermal emission signals to obtain a plurality of interferometric fringe signals, wherein said plurality of interferometric fringe signals includes said first compound interferometric fringe signal;

employing said plurality of interferometric image signals to obtain a corresponding plurality of interferometric image signals; and

,

merging said plurality of interferometric fringe signals to obtain said pixel image of the ROI.

10. A method for obtaining a pixel image of a planetary surface region of interest, comprising:

collecting thermal radiation emissions from a planetary surface region of interest (ROI) by a plurality of spaced antennas to obtain a corresponding plurality of thermal emission signals;

utilizing said plurality of thermal emission signals to obtain a plurality of interferometric fringe signals, wherein said plurality of interferometric fringe signals comprises at least one compound interferometric fringe signal; and

,

employing said plurality of interferometric fringe signals to form a pixel image of the ROI.

11. A method as recited in claim 10, wherein said utilizing step includes:

first combining a plurality of a different pairs of said plurality thermal emission signals to obtain a corresponding plurality of simple interferometric fringe signals.

12. A method as recited in claim 11, wherein said utilizing step further includes:

second combining at least a first pair of said plurality of simple interferometric fringe signals to obtain said at least one compound interferometric fringe signal.

13. A method. as recited in claim 12, wherein said second combining step includes:

combining a plurality of different pairs of said plurality of simple interferometric fringe signals to obtain a plurality of different compound interferometric fringe signals for use in said employing step.

14. A method as recited in claim 11, second combining at least one of said simple interferometric fringe signals with one of said thermal emission signals to obtain said at least one compound interferometric fringe signal.

15. A method as recited in claim 11, wherein said method further includes:

low-pass filtering each of said plurality of sample interferometric fringe signals to separately average each of said simple interferometric fringe signals.

16. A method as recited in claim 11, wherein said method further includes:

upsampling each of said plurality of thermal emission signals separately prior to said utilizing step.

17. A method as recited in claim 11, wherein the method further includes:

time shifting at least one of said plurality of thermal emission signals prior to said utilizing step.

18. A method as recited in claim 10, wherein the method further includes:

low-pass filtering at least one of said plurality of interferometric fringe signals to average said at least one interferometric fringe signal.

19. A method as recited in claim 18, wherein said averaging step includes:

weighting said first interferometric image signal differently than said second interferometric image signal.

20. A method as recited in claim 10, wherein said employing step further includes:

extracting at least one pixel value for each of a plurality of pixel locations from each of at least two of said plurality of interferometric fringe signals to correspondingly obtain at least two interferometric image signals; and

,

merging said at least two interferometric image signals to obtain said pixel image of the ROI.

21. A method as recited in claim 20, wherein said extracting step includes:

applying a different matched filter in corresponding relation to each of said pixel locations for each of said at least two of said plurality of interferometric fringe signals to obtain amplitude components.

22. A method as recited in claim 21, wherein said extracting step further includes:

integrating a plurality of said amplitude components in corresponding relation to each of said pixel locations for each of said at least two of said plurality of interferometric fringe signals to obtain said at least two interferometric image signals.

23. A method as recited in claim 20, wherein said at least two interferometric image signals includes a first and second interferometric image signals, and wherein said merging step includes:

averaging said first interferometric image signal and said second interferometric image signal.

24. A method as recited in claim 10, wherein said method further includes:

positioning said plurality of spaced antennas on a corresponding plurality of space vehicles located in known relative positions over said ROI.

25. A method as recited in claim 24, wherein said positioning step includes:

locating at least two of said plurality of space vehicles so that imaging center axes for at least two of said plurality of spaced antennas define an angle of at least about 2°

therebetween.

26. A method as recited in claim 25, wherein at least one of said utilizing and employing steps are completed at a location remote from said plurality of space vehicles.