Forward model for O2 A-band night glow limb radiance in the mesophere and lower thermosphere

The temperature structure of the global mesosphere and lower atmosphere (MLT) is significant for the study of atmospheric physical, chemical and kinetic processes. Oxygen (O2) A-band airglow (762 nm) can be used as an important tracer to detect the atmospheric temperature structure. The advantage of spatial heterodyne spectrometer (SHS) is high stability, high throughput and high spectral resolution. The fine spectral structure of A-band night glow is detected by limb observation combined with simultaneous split field imaging of atmospheric vertical profile, and the temperature information is retrieved by recovering spectra. Building an accurate forward model is the premise and foundation to obtain the global spaceborne high-resolution atmospheric temperature structure. Based on the A-band night glow radiation mechanism, molecular spectroscopy theory, atmospheric radiation transfer theory and the detection principle of SHS, this paper constructs the forward model of target airglow observation. Furthermore, the sensitivity and analysis of the influencing parameters of the forward model is carried out, which provides a theoretical basis fort the forward modes modification and instrument design. The results show that the forward model described in the paper can satisfy the simulation of A-band night glow spectral radiance observed by SHS at any location through limb observation combined with simultaneous split field of atmospheric vertical profile. That is, the atmospheric tangent range covers 80-120 km and the vertical resolution is better than 2 km. It lays a foundation for the space-borne SHS to detect and accurately retrieve the global temperature structure in MLT region.