Abstract

A compact all-solid-state long-path absorption lidar is being developed for measurement of atmospheric methane. We employ correlation spectroscopy method instead of differential absorption method because the system can be much simpler. The correlation spectroscopy method requires only single laser with multi-mode output. The concept of the measurement system is shown in Fig. 1. The laser pulse is transmitted to the atmosphere, reflected by a topographic target, and received with the telescope. Energies of both the transmitted and received pulses is measured with detectors A and B before and after passing through the correlation cell containing methane. Concentration of methane in the atmosphere can be approximately written by the following equation.

© 1995 IEEE