An eye safe coherent Doppler wind Lidar system with the ability to measure wind velocities along a line of sight originating from the system and extending outwards was developed and tested. Multiple line of sight measurements were incorporated into calculations to ascertain the horizontal and vertical wind vectors. The wind vectors were then used in the calculation of horizontal wind speeds and directions. The system was constructed utilizing components and technologies common to the telecommunication industry to reduce the need for custom components and reduce the cost of the system. The wavelength and power levels were selected to take advantage of existing components and maintain eye safe operation allowing use of the system within public spaces without the need for constant operator and safety personal.
The system was developed in a laboratory and then moved to a research vehicle. The system is polarization maintaining fiber based to enhance coherent heterodyne detection. A balanced detector was utilized to reduce relative intensity noise of the source, and the local oscillator power level was selected to enhance the performance. A beat signal created by the backscattered laser pulse interacting with a local oscillator is analyzed in the frequency domain with the use of a field programmable gate array and the resulting accumulated spectra are further analyzed to determine wind velocities. With spectral accumulation the system is capable of achieving sub-shot noise operation. In the research vehicle the Lidar system can scan the atmosphere at three positions and calculate the vertical and horizontal wind vectors.
Wind measurements made with the system were compared to other meteorological wind instrument measurements in the area with good consistence. Backscatter intensity signals were compared to a direct detection Lidar system and exhibited good agreement. The signals from both systems were processed using a wavelet based planetary boundary layer top determination algorithm and the results for both systems were similar.
|Commitee:||Ahmed, Samir A., Arend, Mark, Dorsinville, Roger, Gross, Barry|
|School:||City University of New York|
|School Location:||United States -- New York|
|Source:||DAI-B 74/03(E), Dissertation Abstracts International|
|Subjects:||Electrical engineering, Remote sensing|
|Keywords:||Coherent, Doppler wind Lidar system, Eye-safe, Wind velocity|
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