DefinePK

Abstract

The down Link signal traveling from satellite to the earth surface need to pass through the layers of the atmosphere situated at an altitude above the earth surface. While passing through these layers the radio wave undergoes some changes in its characteristics. These fluctuations are observed in the troposphere (0 to 12 km containing nitrogen (78 percent) and oxygen (21 percent), with the remaining 1- percent consisting of argon, (.9 percent) and traces of hydrogen ozone (a form of oxygen)), very close to earth surface, so they are called as tropospheric scintillations. There are two types of scintillations called amplitude and phase scintillations. In this paper we are concentrating on estimation of trosposheric amplitude scintillation. While considering lower frequencies (<3GHz) we take the effects of ionosphere into consideration. For higher order frequencies(>10GHz)ionosphere acts as a transparent layer, so only tropospheric scintallations are taken into consideration.Tropospheric amplitude scintillation can be defined as rapid fluctuations in the amplitude of the radio wave caused by changes of refractive index at the altitude. It is caused by humidity and temperature of the atmosphere. The effects of tropospheric scintillation are seasonal and vary from day to day with local climate. In this paper we are estimating the tropospheric amplitude scintillation for ku-band down link signals using RECOMMENDATION ITU-R P.618-8 (Propagation data and prediction methods required for the design of Earth-space telecommunication systems).