In envisioning the frame of future Mars exploration missions, the need for a new series of communications services and performance has become essential. Future missions indeed will carry scientific instruments with higher resolution, higher performance producing higher data volumes to be transmitted to Earth for analysis. SAR, sounder or imaging and high resolution optical instruments are among the most generating data envisaged instruments.

In addition to orbiting systems, future users on the Mars planet will need a data exchange infrastructure and multiple access services. Landers, rovers, and possible human outposts will all need a communication service either local, within themselves, and or with Earth stations. Specifically for the surface, communications dedicated links are being studied to support both design simplicity and data transmission efficiency. These high data volumes, greater than 100 Gbit per day to be transmitted, necessitate of a dedicated communication system specifically designed to operate on Mars orbital ambient.

A system based on a Mars orbiter dedicated to communication - that could also include an on-board scientific payload - is being studied with analysis and definition of possible mission scenarios which will lead to definitions of main links:

• Direct to Earth (DTE) link: it will allow the exchange of large data volumes with Deep Space Network ground stations.

• Proximity Link: it will communicate with Mars surface, interacting with landers, rovers and future surface potential assets as well as connect the orbiter with other potential relay satellites of orbiters in Mars orbit.

DTE link are being defined operating primarily in X/Ka-band and with data transmission above 10 Mb/s. While for the proximity link on Mars both UHF and X-band are considered primary, Ka-band and optical links will be part of a trade-off study to be defined taking into account the evolution of the exploration mission.