Optical Design and Simulation of Spatial Heterodyne Spectroscopy (SHS) for Mesospheric Temperature

Abstract

The mesospheric region exists a lot of complex photochemistry reactions and dynamical processes, which plays an important role in affecting the dynamics in global circulation models and the safety for aircrafts. And gravity wave is a significant dynamical factor in thermodynamic structure and circulation structure. However, because of rare atmosphere in this region, the high-precision measurements on features of mesospheric temperature are insufficient due to a lack of measurement techniques. Design and performance parameters for a high spectral resolution, high spatial resolution in vertical direction, robust and CubeSat-scale spatial heterodyne spectrometer for mesospheric temperature detection are reported. According to the measured value of in-orbit payloads, the subsystem parameters of instrument are described in detail by using spatial heterodyne spectroscopy (SHS) in the O2 atmospheric-band (A-band) (0-0). By optical design and simulation for the instrument with high spectral resolution and spatial resolution in one dimension, we can get the quantitative relationship between the spectral stability and the retrieved temperature precision. For 0.5% relative spectral intensity stability, it has a theoretical temperature precision of 2 K by fitting three peaks, and the signal to noise ratio will be improved with a higher spectral resolution and more emission spectral peaks under the same equivalent noise condition. Finally, orbit attitude control system requirements can be estimated by considering orbit height and the instrument parameters. The scan is not accomplished through controlled nodding or rotation of the spacecraft during short exposure time, and the spectral background signals due to narrow Fraunhofer features and O2-A band absorption lines below 90 km is detectable at SHS spectral resolution. These results will provide a new method to get the global distribution of airglow in wide altitude range (40–130 km) information with simultaneously imaging technique for each view slice of the scene. It will provide basic data for studying the mesospheric temperature and gravity wave activity in the mesospheric atmosphere circulation models.