Abstract
Calibration of coherent lidar sensitivity and applications that use the observed signal magnitude (e.g., backscatter coefficient profiling) require accurate knowledge of the antenna gain. The effective antenna gain includes a contribution due to propagation effects (molecular and particulate extinction and phase distortion due to refractive index inhomogeneities). This contribution can be estimated by measurement of pertinent parameters (e.g., humidity, Cn2) and computation of the resulting loss at the applicable wavelength (10.59 μ). Lidar system contribution to the antenna gain (i.e., the free space gain) is a function of the telescope diameter, the range at which the telescope is focused, beam illumination patterns on the transmitter and receiver apertures and optical system aberrations. Theoretical free space gain curves can be generated when these quantities are known. Observations of aerosol backscatter and discrete target returns have been compared with predictions of antenna gain calculations. Good agreement exists between experiment and theory which indicates that the antenna gain properties of the NOAA Doppler lidar are well understood. Results are also presented on the amplitude calibration of the lidar.