As for detecting the atmosphere, a spectrometer includes five sub-spectrometers (two UV spectrometers, one VIS/IR spectrometer and two SWIR spectrometers) covering 240-2400nm is proposed. The spectrometer will be operated at height of 400km in three viewing modes (Limb, Occultation and Nadir). The spatial resolution is better than 100km2 in the three modes. This article introduces one of the five sub-spectrometers which is based on AOTF (AOTF: Acoustic-Optic Tunable Filter) and working in 1500-2400nm. This scheme utilizes AOTF to select different spectral ranges with 80cm-1 wave number, and then realizes the resolution of 0.1nm (λ/Δλ >105) by a reflection grating. Instead of the parabolic reflector, a transmission light group is selected. The detail design indexes are given and stimulated by Zemax. © 2020 SPIE.