초록 ▼

A weapon-locating ladar system estimates a backward trajectory of an airborne target by using flow field measurements to follow the wake turbulence trailing the airborne target from a position at which the target is detected backwards until the wake is no longer observable. The system may use the ba

A weapon-locating ladar system estimates a backward trajectory of an airborne target by using flow field measurements to follow the wake turbulence trailing the airborne target from a position at which the target is detected backwards until the wake is no longer observable. The system may use the backward trajectory to estimate the point-of-origin of the target. The system may also use the flow field measurements along the backward trajectory to classify the target. Target classification may be used to refine the point-of-origin estimate, to influence counter-fire or to adapt the flow field measurements.

대표청구항 ▼

1. A method for backtracking a trajectory of an airborne target, comprising: illuminating with a laser beam a wake trailing the airborne target from a position at which the target is detected backward until the wake is no longer observable, said laser beam having a spatial pattern and a temporal wav

1. A method for backtracking a trajectory of an airborne target, comprising: illuminating with a laser beam a wake trailing the airborne target from a position at which the target is detected backward until the wake is no longer observable, said laser beam having a spatial pattern and a temporal waveform selected to discriminate wake turbulence from naturally occurring atmospheric phenomena;detecting laser energy backscattered from molecules, aerosols and particulate matter in the volume of air in and around the wake trailing the airborne target;processing the detected laser energy to compute one or more atmospheric flow field images along the wake, each said image including a profile of one or more flow field measurements; andprocessing the profiles of flow field measurements to estimate a backward trajectory of the airborne target from the detected position of the target to the position at which the wake is no longer observable. 2. The method of claim 1, wherein detecting laser energy comprises detecting frequency shifts of the backscattered laser energy, said profile of one or more flow field measurements comprising a spatially resolved radial velocity. 3. The method of claim 1, wherein detecting laser energy comprises detecting a frequency shift as a function of time of the backscattered laser energy, said profile of one or more flow field measurements comprising a spatially resolved radial velocity or derivatives in time or space, moments or functions thereof. 4. The method of claim 1, further comprising: adapting the temporal waveform of the laser beam as the beam backtracks the wake from the detected position. 5. The method of claim 4, wherein the temporal waveform is adapted based on the age of the illuminated portion of the wake to optimize the flow field measurement. 6. The method of claim 4, wherein the temporal waveform is adapted to provide different flow field measurements. 7. The method of claim 4, wherein the temporal waveform is adapted for a three-dimensional range-resolved mode to produce a sequence of flow field images at different range slices to estimate the backward trajectory, and wherein the temporal waveform is adapted for a two-dimensional angle/angle mode to produce a flow field image to estimate the backward trajectory. 8. The method of claim 7, wherein the laser beam illuminates the wake in the range-resolved mode from the detected position backwards along a first portion of the backward trajectory and wherein the laser beam illuminates the wake in the angle/angle mode from that position backwards along a second portion of the backward trajectory until the wake is no longer observable. 9. The method of claim 8, further comprising: switching from the range-resolved mode to the angle/angle mode when the wake is no longer observable in the range-resolved mode. 10. The method of claim 8, further comprising: prior to illumination of the wake with the laser beam, illuminating with a radio frequency beam the airborne target to determine the detected position of the target and an estimated ballistic trajectory for the target; andfusing the estimated ballistic trajectory from the radio frequency beam with the estimates from the laser beam in said range-resolved and angle-angle modes to produce the estimate of the backward trajectory. 11. The method of claim 1, further comprising: adapting a spatial sampling of the detected laser energy in the volume of air in and around the wake in accordance with the flow field measurements. 12. The method of claim 1, wherein the flow field measurements within each flow field image are mapped to a three-dimensional position in Azimuth angle, Elevation angle and range, wherein the backward trajectory is estimated by determining a center of the wake in Azimuth and Elevation angle at each range slice from the flow field measurements and estimating a three-dimensional trajectory through the centers. 13. The method of claim 1, wherein the flow field measurements within the flow field image are mapped to a two-dimensional position in Azimuth angle and Elevation angle, further comprising: providing an estimated ballistic trajectory for the airborne target;estimating a sequence of wake centers in Azimuth angle and Elevation angle from the flow field measurements to provide an angular locus;fitting a curve through the sequence of wake centers of the angular locus to provide the Azimuth angle and Elevation angle components of the backtrack trajectory; andmapping the range coordinate of the estimated ballistic trajectory where the two-dimensional Azimuth angle and Elevation angle projection of the estimated ballistic trajectory is at the minimum angular separation from any point of the curve to provide the range component of the backward trajectory. 14. The method of claim 1, further comprising: projecting the backward trajectory past the position at which the wake is no longer observable to estimate a point-of-origin of the airborne target. 15. The method of claim 1, further comprising: processing the flow field measurements to assign a target class of the airborne target. 16. The method of claim 15, further comprising: projecting the backward trajectory past the position at which the wake is no longer observable to estimate a point-of-origin of the airborne target; andrefining the estimate of the point-of-origin based on the assigned target class. 17. The method of claim 15, further comprising: projecting the backward trajectory past the position at which the wake is no longer observable to estimate a point-of-origin of the airborne target;directing counter fire at the estimated point-of-origin; andusing the assigned target class to control the counter fire. 18. The method of claim 15, further comprising: using the assigned target class to adapt the temporal waveform of the laser beam. 19. The method of claim 15, further comprising: illuminating with a either a radio frequency beam or the laser beam the airborne target to extract target measurements; andusing both the flow field measurements of the turbulent wake and the target measurements to assign the target class. 20. A method for backtracking a trajectory of an airborne target, comprising: illuminating with a radio frequency beam the airborne target to determine a detected position of the target;illuminating with a laser beam a wake trailing the airborne target from the detected position backward until the wake is no longer observable, said laser beam having a spatial pattern and a temporal waveform selected to discriminate wake turbulence from naturally occurring atmospheric phenomena;detecting laser energy backscattered from molecules, aerosols and particulate matter in the volume of air in and around the wake trailing the airborne target;processing the detected laser energy to compute one or more atmospheric flow field images along the wake between the detected and observable positions, each said image including a profile of one or more flow field measurements;processing the profiles of flow field measurements to estimate a backward trajectory of the airborne target from the detected position of the target to the position at which the wake is no longer observable;projecting the backward trajectory past the position at which the wake is no longer observable to estimate a point-of-origin of the airborne target; anddirecting counter fire at the estimated point-of-origin. 21. The method of claim 20, wherein illumination of the airborne target with the radio frequency beam provides an estimated ballistic trajectory, further comprising: adapting the temporal waveform of the laser beam for a three-dimensional range-resolved mode from the detected position backwards to produce a sequence of flow field images at different range slices to estimate the backward trajectory;adapting the temporal waveform of the laser beam for a two-dimensional angle/angle mode from that position backwards to the position at which the wake is no longer observable to produce a flow field image to estimate the backward trajectory, andfusing the estimated ballistic trajectory from the radio frequency beam with the estimates from the laser beam in said range-resolved and angle-angle modes to produce the estimate of the backward trajectory. 22. The method of claim 20, further comprising: processing the flow field measurements to assign a target class of the airborne target; andusing the assigned target class to perform at least one of the following steps, refine the estimate of the point-of-origin;control the counter fire; andadapt the temporal waveform. 23. A system for backtracking a trajectory of an airborne target, comprising: a laser transmitter configured to generate a laser beam having a spatial pattern and a temporal waveform selected to discriminate wake turbulence from naturally occurring atmospheric phenomena, said laser beam illuminating a wake trailing the airborne target from a position at which the target is detected backward until the wake is no longer observable;a ladar receiver comprising one or more detectors that detect laser energy backscattered from molecules, aerosols and particulate matter in the volume of air in and around the wake trailing the airborne target;a ladar signal processor configured to process the detected laser energy to compute one or more atmospheric flow field images along the wake between the detected and observable positions, each said image including a profile of one or more flow field measurements; anda system processor configured to process the profiles of flow field measurements to estimate a backward trajectory of the airborne target from the detected position of the target to the position at which the wake is no longer observable. 24. The system of claim 23, further comprising: a radar system configured to illuminate the airborne target with a radio frequency beam to determine the detected position and to provide an estimated ballistic trajectory for the airborne target,wherein said laser transmitter, ladar receiver, signal processor and system processor are configured to adapt the temporal waveform of the laser beam for a three-dimensional range-resolved mode from the detected position backwards to produce a sequence of flow field images at different range slices to estimate the backward trajectory and to adapt the temporal waveform of the laser beam for a two-dimensional angle/angle mode from that position backwards to the position at which the wake is no longer observable to produce a flow field image to estimate the backward trajectory, andwherein the system processor is configured to fuse the estimated ballistic trajectory from the radio frequency beam with the estimates from the laser beam in said range-resolved and angle-angle modes to produce the estimate of the backward trajectory.