It was necessary to design a two-way radio link between Earth and our GPS system located in orbit around Mars. This link will serve as a means for exchanging digital telemetry, control, sensor, and synchronization data. Because of the Earth-Mars orbital system, this link can not work at every moment because the sun is sometimes right between the two planets. The minimum travel time of the wave is around 3 minutes and 7 seconds which corresponds to the perihelion opposition, 56 million kilometers separates Mars and the Earth and the maximum travel time of the wave is around 20 minutes and 57 secondes which corresponds to a separating distance of 380 million kilometers!

In order to save energy, only one satellite at a time can communicate with Earth, the one
which has the best link budget estimation.

The system works in the Ka-band [26.5GHz,40GHz] in order to maximize the gain in the link budget. The up-link carrier frequency, communication from Mars to Earth, is 32Ghz and the down-link carrier frequency, communication from Earth to Mars, is 34Ghz.This link has been designed to work at a minimum data rate of 1Mbps and a 100Mhz bandwidth is used. According to Shannon, we could be able to communicate reliably with a Signal-to-Noise ratio of - 28.5dB: