Summary This paper studies the effects of fog and scintillation attenuations on the performance of the vertical free‐space optical (FSO) link from the Earth to low Earth orbit (LEO) satellite. FSO link performance was investigated under different foggy conditions and turbulence by calculating the power received, achieved data rate, and link margin. Different parameters were studied such as the wavelength, the transmitted power, the divergence angle, and the diameter of receiving optical antenna. The results show that the FSO performance can be improved using 1,550‐nm wavelength, increasing the transmitted power to a range of 5 mW and reducing the divergence angle to a range of 1 μrad.

Free space optics uplink to Low Earth Orbit (LEO) satellite with 500Km distance and 1.55μm wavelength is evaluated with 10Gbps data rate and 70W transmitted power. The equivalent effects for all weather parameters are given by the measured visibility used to determine the weather attenuations by using Mie-Scattering, in this proposed. These high attenuations reduce the availability performance of the FSO uplink. The scintillation (Cn2) had estimated using a compatible model of Cairo weather, and the turbulence effect (beam divergence) becomes very weak by using the aperture diameter of the receiver higher than the maximum optical spot size due to turbulence and divergence. During the year 2019, the visibility must be greater than 5Km, and weak scintillation turbulence is Cn2<0.00566∗10−16 m-2/3at distance 500Km. The availability evaluations based on predicted attenuation due to weather and turbulence using data measured in Cairo and the effects of all parameters on the performance of FSO are discussed. The required transmitted power must be related to the expected visibility. In year 2019, the availability of link becomes 99.9945%.

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