US 8,077,088 B2 · Method for single satellite geolocation of emitters using an ambiguous interferometer array

Abstract

A method of locating a terrestrial emitter of electromagnetic radiation in the midst of a plurality of emitters in a satellite in orbit about the earth which utilizes a location estimation and location probability determination process with respect to each possible emitter site and its corresponding error region and then using both feedback and feed forward interaction between location and phase ambiguity resolution processes to generate resolved phase from emitter location, update emitter location or some or all of the emitters, and subsequently utilizing the probabilities thus determined to produce a single estimate of the desired emitter's location.

Claims26

Dependent claims

A method of determining the actual location of an emitter by an array of sensors, each sensor detecting signals from the emitter, comprising the steps of:

(a) measuring a set of signals from the emitter at an initial location of the array of sensors to determine data indicative of emitter site location;
(b) determining estimates of all emitter site locations possible, within measurement error of the sensor array, associated with the measured data;
(c) determining a probability, based on predetermined data, for each possible emitter site location estimates that each possible location estimate is the actual emitter site location;
(d) generating an estimate of the actual emitter site location based on the probabilities determined in step (c);
(e) moving the array of sensors relative to the emitter;
(f) measuring another set of signals from the emitter at the moved array location to determine data indicative of emitter site location;
(g) for each emitter site location determined in step (b) predict the data indicative of emitter site location of step (f);
(h) associate the measured data indicative of emitter site location of step (f) with the estimates of all emitter site locations of step (b) by utilizing the data of step (g);
(i) alter the measured data of step (f) by the data of step (h) to within measurement error of the sensor array;
j) generating updated predicted data of emitter site location based on the altered measurement data of step (i);
and
(k) compare the updated predicted data from step j) with the measured data from step (f) to determine the probability of step (c).

9 more elements

A method of locating a terrestrial emitter of electromagnetic radiation by a satellite in an orbit about the earth, comprising the steps of:

(a) detecting a signal from the emitter at the satellite during a first predetermined dwell time;
(b) measuring the difference in phase of the wavefront of the detected signal at pairs of antennas selectively located on the satellite;
(c) generating a set of all possible phase measurement ambiguity integers, one for each antenna pair, consistent with the frequency of the signal from said emitter and the orientation of the pair of antennas during step (b);
(d) determining all possible direction of arrival (DOA) vectors by resolving the phase with each ambiguity integer;
(e) determining and storing estimates of all possible emitter site locations associated with the DOA vectors wherein one of said estimates is, within the measurement error, the actual emitter site location;
(f) initializing a location estimator for possible emitter site location determined in step (e);
(g) detecting a signal from the emitter during a second predetermined dwell time following the first dwell time wherein the satellite has moved in its orbit relative to the emitter, and measuring the phase difference during the second time interval according to step (b);
(h) predicting a new set of DOA vectors, utilizing the stored emitter estimated positions from step (e) and the satellite orbital position following the phase difference measuring step in step (g);
(i) predicting a new set of phase measurement ambiguity integers with each predicted new DOA vector consistent with the orientation of said pair of antennas during the second dwell time;
(j) resolving the measured phase difference of step (g) with each ambiguity integer of the set of phase measurement ambiguity integers generated in step (i);
(k) inputting the resolved measured phase differences of step (i) into the location estimator initialized in step (f), and updating each estimate of emitter site location initialized in step (f);
(l) replacing each stored location estimate of step (e) with the updated emitter site location estimate;
(m) determining a probability for each updated emitter site location estimate by determining a likelihood that each location estimate is the actual emitter site location of the emitter;
(n) generating an estimate of the actual emitter site location based on the probability determined in step (m);
and
(o) repeating step (g) through step (n) until the estimate from step (n) converges, within measurement error and a predetermined processing error tolerance, to the actual emitter location.

13 more elements

A method of locating terrestrial emitter of electromagnetic radiation on the earth's surface using an interferometer array mounted on a satellite in orbit above the earth's surface, comprising the steps of:

(a) measuring the phase difference of a signal wavefront of signals from the emitters intercepted by the array and producing a set of direction of arrival (DOA) vectors for the detected emitter signals;
(b) generating a set of all possible phase measurement integers, consistent with emitter intercept signals during the phase difference measuring step (a);
(c) determining all possible DOA vectors from the measured phase utilizing all the ambiguity integers;
(d) determining and storing estimates of all possible emitter site locations associated with the DOA vectors determined;
(e) moving the satellite relative to the emitter;
(f) measuring a new set of phase differences;
(g) adjusting the stored estimates of emitter site locations of step (d) so as to account for the earth's rotation during the orbital movement of the satellite in step (e);
(h) generating a new set of DOA vectors utilizing the adjusted stored emitter site location estimates and satellite orbital position at the moved satellite position;
(i) generating a new set of ambiguity integers for the new set of DOA vectors;
(j) resolving the measured phase differences in step (f) with the new set of ambiguity integers;
(k) updating each estimate of possible emitter site locations established;
(l) replacing each stored location estimate in step (d) with the updated emitter site location estimate;
(m) determining a value of the probability that one of the updated emitter site locations is a true location;
and
(n) generating an estimate of the true emitter site location utilizing probability values determined in step (m).

12 more elements

A method of locating a terrestrial emitter of electromagnetic radiation on the earth's surface using an antenna array interferometer mounted on a satellite, the satellite being in an orbit producing translational motion of the array relative to said emitter, the method comprising the steps of:

(a) detecting a transmitted signal from the emitter during a first position of the satellite;
(b) measuring phase difference of a signal wavefront of a signal intercepted by the antenna array on the satellite;
(c) generating a set of all possible phase measurement ambiguity integers, consistent with emitter frequency and orientation of the antenna array;
(d) determining all possible direction of arrival (DOA) vectors utilizing all the ambiguity integers;
(e) determining and storing estimates of all possible emitter site locations associated with the DOA vectors;
(f) detecting a transmitted signal from the emitter during a second position of the satellite;
(g) measuring a second set of phase differences and generating a second set of ambiguity integers per steps (b) and (c);
(h) adjusting the stored previous estimate of all possible emitter site locations so as to account for the earth's rotation during the second position of the satellite;
(i) generating a second set of DOA vectors utilizing the adjusted stored emitter site location estimates and satellite orbital position during the second position of the satellite;
(j) generating a new set of ambiguity integers for the second set of DOA vectors;
(k) updating the measured phase differences with the new set of ambiguity integers;
(l) updating each estimate of possible emitter site locations by the respective phase differences of step (k);
(m) replacing each stored emitter site location estimate of step (e) with respective updated emitter site location estimates of step (l);
(n) determining the probability that one of the updated emitter site locations is an actual emitter site location;
and
(o) generating an estimate of the actual emitter site location utilizing probability values determined in step (n).

13 more elements

Dependencies are inferred from the claim text.

Facts

Application

12/198,787Filed 26 Aug 2008 · continuation

Priority

30 May 2007

Published

US 2009/0079634 A126 Mar 2009

Granted

13 Dec 2011

Term ends

Not estimatedThe source records don’t support an estimate.

Classification4 codes

G01S 5/12
Using radio waves: by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial
G01S 3/48
Using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems: the waves arriving at…
G01S 5/04
Using radio waves: position of source determined by a plurality of spaced direction-finders
G01S
Radio direction-finding

Abstract

Claims26

Dependent claims

A method of determining the actual location of an emitter by an array of sensors, each sensor detecting signals from the emitter, comprising the steps of:

(a) measuring a set of signals from the emitter at an initial location of the array of sensors to determine data indicative of emitter site location;
(b) determining estimates of all emitter site locations possible, within measurement error of the sensor array, associated with the measured data;
(c) determining a probability, based on predetermined data, for each possible emitter site location estimates that each possible location estimate is the actual emitter site location;
(d) generating an estimate of the actual emitter site location based on the probabilities determined in step (c);
(e) moving the array of sensors relative to the emitter;
(f) measuring another set of signals from the emitter at the moved array location to determine data indicative of emitter site location;
(g) for each emitter site location determined in step (b) predict the data indicative of emitter site location of step (f);
(h) associate the measured data indicative of emitter site location of step (f) with the estimates of all emitter site locations of step (b) by utilizing the data of step (g);
(i) alter the measured data of step (f) by the data of step (h) to within measurement error of the sensor array;
j) generating updated predicted data of emitter site location based on the altered measurement data of step (i);
and
(k) compare the updated predicted data from step j) with the measured data from step (f) to determine the probability of step (c).

9 more elements

A method of locating a terrestrial emitter of electromagnetic radiation by a satellite in an orbit about the earth, comprising the steps of:

(a) detecting a signal from the emitter at the satellite during a first predetermined dwell time;
(b) measuring the difference in phase of the wavefront of the detected signal at pairs of antennas selectively located on the satellite;
(c) generating a set of all possible phase measurement ambiguity integers, one for each antenna pair, consistent with the frequency of the signal from said emitter and the orientation of the pair of antennas during step (b);
(d) determining all possible direction of arrival (DOA) vectors by resolving the phase with each ambiguity integer;
(e) determining and storing estimates of all possible emitter site locations associated with the DOA vectors wherein one of said estimates is, within the measurement error, the actual emitter site location;
(f) initializing a location estimator for possible emitter site location determined in step (e);
(g) detecting a signal from the emitter during a second predetermined dwell time following the first dwell time wherein the satellite has moved in its orbit relative to the emitter, and measuring the phase difference during the second time interval according to step (b);
(h) predicting a new set of DOA vectors, utilizing the stored emitter estimated positions from step (e) and the satellite orbital position following the phase difference measuring step in step (g);
(i) predicting a new set of phase measurement ambiguity integers with each predicted new DOA vector consistent with the orientation of said pair of antennas during the second dwell time;
(j) resolving the measured phase difference of step (g) with each ambiguity integer of the set of phase measurement ambiguity integers generated in step (i);
(k) inputting the resolved measured phase differences of step (i) into the location estimator initialized in step (f), and updating each estimate of emitter site location initialized in step (f);
(l) replacing each stored location estimate of step (e) with the updated emitter site location estimate;
(m) determining a probability for each updated emitter site location estimate by determining a likelihood that each location estimate is the actual emitter site location of the emitter;
(n) generating an estimate of the actual emitter site location based on the probability determined in step (m);
and
(o) repeating step (g) through step (n) until the estimate from step (n) converges, within measurement error and a predetermined processing error tolerance, to the actual emitter location.

13 more elements

(a) measuring the phase difference of a signal wavefront of signals from the emitters intercepted by the array and producing a set of direction of arrival (DOA) vectors for the detected emitter signals;
(b) generating a set of all possible phase measurement integers, consistent with emitter intercept signals during the phase difference measuring step (a);
(c) determining all possible DOA vectors from the measured phase utilizing all the ambiguity integers;
(d) determining and storing estimates of all possible emitter site locations associated with the DOA vectors determined;
(e) moving the satellite relative to the emitter;
(f) measuring a new set of phase differences;
(g) adjusting the stored estimates of emitter site locations of step (d) so as to account for the earth's rotation during the orbital movement of the satellite in step (e);
(h) generating a new set of DOA vectors utilizing the adjusted stored emitter site location estimates and satellite orbital position at the moved satellite position;
(i) generating a new set of ambiguity integers for the new set of DOA vectors;
(j) resolving the measured phase differences in step (f) with the new set of ambiguity integers;
(k) updating each estimate of possible emitter site locations established;
(l) replacing each stored location estimate in step (d) with the updated emitter site location estimate;
(m) determining a value of the probability that one of the updated emitter site locations is a true location;
and
(n) generating an estimate of the true emitter site location utilizing probability values determined in step (m).

12 more elements

(a) detecting a transmitted signal from the emitter during a first position of the satellite;
(b) measuring phase difference of a signal wavefront of a signal intercepted by the antenna array on the satellite;
(c) generating a set of all possible phase measurement ambiguity integers, consistent with emitter frequency and orientation of the antenna array;
(d) determining all possible direction of arrival (DOA) vectors utilizing all the ambiguity integers;
(e) determining and storing estimates of all possible emitter site locations associated with the DOA vectors;
(f) detecting a transmitted signal from the emitter during a second position of the satellite;
(g) measuring a second set of phase differences and generating a second set of ambiguity integers per steps (b) and (c);
(h) adjusting the stored previous estimate of all possible emitter site locations so as to account for the earth's rotation during the second position of the satellite;
(i) generating a second set of DOA vectors utilizing the adjusted stored emitter site location estimates and satellite orbital position during the second position of the satellite;
(j) generating a new set of ambiguity integers for the second set of DOA vectors;
(k) updating the measured phase differences with the new set of ambiguity integers;
(l) updating each estimate of possible emitter site locations by the respective phase differences of step (k);
(m) replacing each stored emitter site location estimate of step (e) with respective updated emitter site location estimates of step (l);
(n) determining the probability that one of the updated emitter site locations is an actual emitter site location;
and
(o) generating an estimate of the actual emitter site location utilizing probability values determined in step (n).

13 more elements

Dependencies are inferred from the claim text.

Method for single satellite geolocation of emitters using an ambiguous interferometer array

Life of this patent

Abstract

Claims26

Method for single satellite geolocation of emitters using an ambiguous interferometer array

Life of this patent

Abstract

Claims26