Selection and Justification of Optimal Spectral Wavelengths for Control of Methane Emission from an Advanced Nanosatellite

Abstract

The choice and justification of optimal wavelengths of spectral radiance density registration for the task of monitoring methane emissions in the atmosphere from the orbit of an artificial satellite by a passive optical sensor in the spectral region near 1.65 μm have been performed. Mathematical modelling of the spectra recorded by the optical sensor for tropical and subarctic atmospheric models of the Earth’s atmosphere, different widths of the spectral function of the acousto-optic spectrometer, and different solar zenith angle were performed. It is assumed that methane emissions in the Earth’s atmosphere will be monitored from a promising nanosatellite (weighing less than 6 kg) using an acousto-optic spectrometer, which uses two narrow (0.1 nm and 0.5 nm) wavelengths of radiation registration to implement a differential method of absorption spectroscopy based on acousto-optic filtering. A criterion for selecting optimal wavelengths for monitoring the integral methane content in the atmosphere from the orbit of the artificial satellite is proposed. The values of the central wavelengths of optimal wavelengths for recording the energy brightness of scattered radiation for the width of the spectral function of the acousto-optic spectrometer in range (0.0, 0.1, 0.2 and 0.5) nm have been obtained. It is shown that the choice of the optimal pair of wavelengths is determined by the width of the spectral function of the sensor, depends insignificantly on the model of the Earth’s atmosphere (tropical or subarctic model) and does not depend on the solar zenith angle in range (0–80) angular degree.