Investigation of the possibilities of increasing the resolution of lidars in the infrared wavelength range for monitoring methane in the atmosphere

Abstract

The paper deals with the resolution of an optical lidar for measuring the background concentration of methane in the atmosphere both on surface horizontal paths with reflection of an optical signal from natural objects and on vertical paths, when an optical signal is reflected from cloud layers with extrapolation to low space orbits. It was shown using simulations that in the case of measurements from a low space orbit, the signal accumulation time can be reduced to 1 second or less due to the large signal attenuation at the center of the absorption line in the atmospheric air column. For a signal accumulation time of 1 s, the horizontal resolution along the horizontal coordinate will be ∼8 km at a satellite orbital velocity of ∼8 km / s. The vertical resolution for measurements from space orbit can be ∼ 1 km if the accuracy of measuring the absorption line broadening is ∼0.006 nm (10%). On the horizontal paths, the experimental results are in good agreement with the simulation results. Broadening the emission line of the lidar transmitter by a factor of ∼3 makes it possible to increase the radiated power at the considered wavelength ∼ 1653 nm, improve the energy potential of the device, and bring the horizontal resolution to 5-10 meters on the speed of lidar beam, corresponding to the speed of the helicopter.