Parametric Study of a 10.6-micro Laser Radar

A parametric study of a 10.6-micro laser radar using heterodyne detection is presented. Returns from various noncooperative targets have been obtained at ranges of up to 8 km. The radar equipment uses an offset local oscillator frequency in order to avoid homodyne operation. Measurements of signal-to-noise ratio over a 1.06-km range show that the system is within a factor of 4 of quantum-limited operation. For visibility ranging from 305 m to 120 km the scattering coefficient is found to range from 1.05 x 10(-8) m(-1) to 4.21 x 10-(7) m-(1). The depolarization of returns from targets and from atmospheric aerosols is found to be less than approximately 20% for targets and near zero for aerosols. Both atmospheric and target scintillation have been studied, with the conclusion that target-induced scintillation is generally larger. Atmospheric scintillation is found to be much less severe than for visible laser wavelengths. Finally, measurements of the frequency broadening introduced by the scanner are presented. Good agreement with a si ple theoretical model involving Doppler shift from the scanning mirror is obtained.