UAV Onboard Third Harmonic Technique Laser Spectrometer for Near Infrared Atmospheric Absorption Lines Detection

We describe the UAV onboard third harmonic technique laser spectrometer for near infrared atmospheric absorption lines detection. We use 2 mW DFB laser with current and temperature frequency modulation and InGaAs PIN photodiode with 1 mm sensitive area and 60 nA dark current to detect the backscattered laser radiation. We use the second harmonic demodulation of laser signal and peak detector to obtain the absorption line presence signal.