Atmospheric turbulence data optical system
An atmospheric turbulence data optical LIDAR system for computation of wind velocity includes a laser ( 16 ) to transmit one or more beams to a target, an optical head ( 10 ) including a transmitting optics ( 12 ) and a collecting lens ( 14 ) for receiving one or more corresponding beam returns from the target. A detection system ( 18 ) includes a multi-element detector array at near a focal plane of the collecting lens. For each element of the multi-element detector array there is a specific optical path in the atmosphere leading from the laser to the target and back from the target to the element. A processor measures ( 20 ) signal fluctuations of an element of the multi-element detector array and computes therefrom crosswind velocity of wind in the atmosphere. The processor calculates turbulence strength changes.
1. An atmospheric turbulence data optical LIDAR system for computation of wind velocity comprising:
two LIDAR systems with different line-of-sight paths at an angle to each other, each of said LIDAR systems comprising:
a laser adapted to transmit one or more beams to a target;
an optical head comprising an optical transmitter and an optical receiver for receiving one or more corresponding beam returns from the target;
a detection system comprising a multi-element detector array at near a focal plane of the optical receiver, wherein for each element of the multi-element detector array there is a specific optical path in the atmosphere leading from the laser to the target and back from the target to the element;
wherein a field of view of each element of the multi-element detector array is reduced to 1/n of the laser beam divergence, wherein n is the number of elements in the multi-element detector array; and
a processor operative to measure signal fluctuations of an element of the multi-element detector array and compute therefrom crosswind velocity of wind in the atmosphere, wherein the processor is operative to calculate turbulence strength changes;
wherein line-of-sight path axes of said transmitters and said receivers coincide; and
wherein said processor is operative to perform wind profiling by time-delayed high speed sampling of signals from different distances detected by said detection system, said processor using a sampling-rate digitizer with n simultaneously sampled channels corresponding to said number of elements in said multi-element, detector array.
2. The system according to claim 1 , wherein a time between samplings of said sampled channels and a pulse length of said laser define a space resolution limit.
3. A method for computation of wind velocity comprising using the system of claim 1 to compute crosswind velocity of wind in the atmosphere.
4. The method according to claim 3 , wherein the laser beam propagates through a turbulent atmosphere and is scattered by atmospheric aerosol, and wherein the turbulent atmosphere is composed of discrete blobs or eddies, each of which has a different refractive index than its neighbors due to temperature inhomogeneity of the atmosphere, and wherein an interaction of the laser beam with the turbulent atmosphere leads to random amplitude and phase variations, resulting in fluctuations in the intensity distribution of the laser beam, and wherein backscattering from aerosol, influenced by the turbulent atmosphere, is registered by the multi-element detector array, and further comprising measuring intensity fluctuations on each element of the multi-element detector.
5. The method according to claim 3 , further comprising providing a 3-axis wind vector for computing true aircraft speed, sideslip and angle of attack.
6. The method according to claim 1 , comprising three LIDAR systems with different line-of-sight paths at an angle to each other, wherein the method includes computing true aircraft speed, sideslip and angle of attack, a rolling and a vertical aircraft speed.