Fabry-Pérot interferometry is a well-established method of interrogating the lower thermosphere region of the Earth’s atmosphere. Nighttime measurements of visible and infrared airglow in four cardinal directions and Zenith are inverted to yield wind speed and direction as well as temperature. A 300 mm focal length lens images ring patterns on a deep-cooled CCD achieving 11 full rings on the 13.3 mm square sensor in our instrument. The Fabry-Pérot Interferometer structure is based on a legacy design which passes emissions through a narrow-band filter, an etalon, and a focusing lens to image onto a CCD focal plane array, in contrast to traditional interferometers which often rely on telecentric filtering with complex optical arrangements prior to the light entering the etalon. The quality of the ring pattern greatly influences the residual error of processing the raw data into derived quantities. Our new instrument employs a novel apochromatic lens system developed at Keo Scientific that yields lower vignetting and sharper rings over an extended wavelength range, enabling higher quality measurements over the entire range of wavelengths. Examples of ring patterns and derived quantities from our first f/3, 100 mm diameter etalon instrument are presented here. The instrument was first deployed in July, 2019, by the Chinese Academy of Sciences Institute of Geology and Geophysics at their field-station in Mohe, Heilongjiang in Northern China.
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