Influence of the Transmission Medium

These data will determine the spectral range of ground-based astronomical observations. A corresponding curve for horizontal atmospheric absorption at sea level over a distance of one nautical mile (1.8 km) is given in Fig. 6.53. This curve is of interest when considering free-laser-beam optical communica- 

The spectral distribution of the sun s radiation is shown in Fig. 6.51, both outside the atmosphere and at sea-level with different absorption bands indicated. The vertical transmission of the earth s atmosphere, in- 

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