Limitation of Laser Satellite Communication Due To Vibrations and Atmospheric Turbulences


In this research, we analyze the effects of vibrations and the atmospheric onturbulence for a broadband laser satellite down link (BLSDL). The use of opticalradiation as a carrier between satellites and in satellite-to-ground links enablestransmission using very narrow beam divergence angles. Due to the narrow beamdivergence angle and the large distance between the satellite and the groundstation or any object the pointing is a complicated process. Further complicationresults from vibration of the pointing system caused by fundamental mezchanisms: tracking noise created by the electro-optic tracker and vibrations caused byinternal satellite mechanical mechanisms. Additionally an in homogeneity in thetemperature and pressure of the atmosphere leads to variations of the refractiveindex along the transmission path. These variations of refractive index as well asintroducing other external noise, pointing vibrations, can cause fluctuations in theintensity and the phase of the received signal leading to an increase in link errorprobability. In this research, we develop a bit error probability (BEP) model thattakes into account both pointing vibrations and turbulence-induced high amplitudefluctuations (i.e., signal intensity fading) in a regime in which the receiveraperture antenna (Do) is smaller than the turbulence coherence diameter (do), theresults indicate that the satellite broad band laser down link with the receiver canachieve a BEP of 10-9 and data rate of lGbps with normalized pointing vibration ofand turbulence withAfter reducing these limitation of laser satellites and compensatesrelatively most atmospheric error probabilities due to atmospheric turbaulences(BEPS) or variation of refractive index by using for ward feeding under finetracking which designed to decrease the residual jitter influencies or by usingdirectional laser beam or introducing feeding forward compensation method andadaptive techniques to reduce the effect of system vibrations [12].