Path Attenuation due to Orbital and Latitude Elevation

FCCatten2.png

The atmosphere attenuates microwaves. This graph is from FCC bulletin 70, Millimeter Wave Propagation: Spectrum Management Implications , July 1997.

The effective depth of the atmosphere ( Sea level pressure divided by sea level density and gravity ) is 8.5km, and microwaves arriving from space at an elevation angle of E travel through 8.5 / cos(E) kilometers of atmosphere. The attenuation trends upwards with frequency, with absorption peaks at frequencies where oxygen or water molecules resonate. The attenuation at 70GHz is 0.79dB/km, so the attenuation is 6.32 dB / cos(E), a factor of 4.29 at zenith (E = 90 °) and 18.4 at 30 ° elevation.

Find thinsat density versus elevation

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