Velocity measurement of hard target in angle-tuned Doppler wind lidar

The initial operating position was set by means of tuning Fabry-Pérot etalon angle, and the accuracy of angle tuning was 10 μrad. At this position the reference signal and echo signal were measured with monostatic polarization light splitting. The longitudinal-mode Nd:YAG laser with wavelength of 1.064 μm was used with the probability of single longitudinal mode greater than 98%, and long-time stability of laser frequency about 10^-7. The hard target was placed at the focal spot of the collimating mirror. The reference and echo signal were separately measured when the hard target was still, in positive rotation and negative rotation. The correction factor about the angle of reference signal is obtained as 1.1949, by the relation between reference and echo signal when the hard target is still. The measured results indicate the velocity error is less than 0.5 m/s between measured value and true value with this correction factor.