Fig. 1. Middle and upper atmosphere background detection model. (a) Limb view; (b) slant view

Fig. 2. The comparison of 2320‒2400 cm^-1 band limb background radiance profile simulated by SHARC and the measured background radiance profile. (a) Daytime condition; (b) night condition

Fig. 3. The comparison of limb background radiance profile simulated by SHARC and MODTRAN. (a) 3‒5 µm; (b) 8‒12 µm

Fig. 4. The limb radiance spectra of 3‒5 μm band at daytime and nighttime at different tangent altitude. (a) Daytime condition; (b) night condition

Fig. 5. The differences of 3‒5 μm band middle and upper atmospheric background radiance profiles in different seasons at different latitude. (a) Low latitude daytime; (b) low latitude night; (c) middle latitude daytime; (d) middle latitude night; (e) high latitude daytime; (f) high latitude night

Fig. 6. Comparison of 3‒5 μm band atmospheric background radiance profiles at different solar zenith angles

Fig. 7. Comparison of 3-5 μm band atmospheric background radiance profiles at different solar zenith angles and observer zenith angles. (a) Different solar zenith angles; (b) different observer zenith angles

Fig. 8. The relationship between long and short path radiance and the ratio of path length

Fig. 9. Atmospheric background radiance profiles under different solar zenith angles and azimuth angles. (a) Long path; (b) short path

Fig. 10. Radiation characteristics of long path and short path

Fig. 11. Infrared imaging model of detector. (a) Overall schematic diagram; (b) imaging plane coordinate system

Fig. 12. Simulation results of 3‒5 μm band daytime infrared radiation scene in middle latitude summer (limb view, 150 km). (a) (b) 31‒70 km; (c) (d) 70‒102 km; (e) (f) 102‒149 km

Fig. 13. Simulation results of the observer zenith angle between 77°‒89° infrared radiation scene (slant view,150 km). (a) Daytime condition; (b) night condition

Fig. 14. Simulation results of 3‒5 μm band daytime and night infrared radiation scene in middle latitude summer (limb view, 300 km). (a) 52‒112 km daytime; (b) 139‒188 km daytime; (c) 52‒112 km night; (d) 139‒188 km night