In satellite communication, the Brazilians rains distributions are presented like limited factor in the viability analyze of VSAT networks (Very Small Aperture Terminal) in the bands Ka and Ku. The aim of the work is analyze the unavailable caused by VSAT rains with star topology used in Brazil to some kinds of service, like telephone and data transmission and TV, using conjectural scenes on the satellite s terminal stations with transponders in the bands Ka and Ku and the real characteristics of the equipments and systems. One of the objectives is analyze the influence of the attenuation system. For it were used the last two versions models rainy attenuation that has been recommended by UIT-R for applications in engineering. Completing this objective, were also analyzed the influence precipitation taxes data for Brazil using this models, have been used two fonts: the recommendation P.837 from UIT-R and regional measured realized by CETUC. Other objective was the comparison between unavailable esteem values with maxim limits recommended what allows having conclusions about the viability of these systems in Brazil. Concluding the study, a second case was analyzed corresponding a system. The scene is composed by from other satellite (PAS-9), by the way, with the same localizations. The difference between both are: the first one has a bigger tax of transmission for being used analyze of the unavailable one model of attenuation for regional rains, made by CETUC based on measure data from Brazil. One similar analyze was made considering an actual model of UTI-R for final comparisons.