Atmospheric window fefers to some bands of celestial radiation that can penetrate the atmosphere. Due to the absorption and reflection of radiation by various particles in the earth's atmosphere, only radiation from celestial bodies in certain wavebands can reach the ground. Divided into optical window, infrared window and radio window according to their respective scopes. Infrared window Water vapor molecules are the main absorbers of infrared radiation. Strong water vapor absorption bands are located at 0.71～0.735μ (micron), 0.81～0.84μ, 0.89～0.99μ, 1.07～1.20μ, 1.3～1.5μ, 1.7～2.0μ, 2.4～3.3μ, 4.8～8.0μ. An absorption band of carbon dioxide appears at 13.5～17μ. The gaps between these absorption bands form some infrared windows. The widest infrared window is at 8-13μ (there is an absorption band of ozone near 9.5μ). 17～22μ are translucent windows. After 22μ until the wavelength of 1 millimeter, due to the severe absorption of water vapor, it is completely opaque to observers on the ground. But in places with high altitude and dry air, the radiation transmittance of 24.5～42μ can reach 30～60%. At 3.5 kilometers above sea level, radiation of 330-380μ, 420-490μ, 580-670μ (transmittance of about 30%) can be observed, and 670-780μ (about 70%) and 800-910μ (about 30%) can be observed. 85%) radiation.