Telecommunication system specific to high temperature environment for JAXA Mercury exploration program

BepiColombo is the joint Mercury exploration program between JAXA (Japan Aerospace Exploration Agency) and ESA (European Space Agency). MMO (Mercury Magnetospheric Orbiter) is JAXA's satellite in this program. She requires a telecommunication system that survives a harsh heat environment surrounding Mercury. She will stay in a polar orbit circulating Mercury for a year for continuous observations of Mercury magnetosphere. MMO has an X-band telecommunication system. We newly developed a high gain antenna for the use of her daily operations and wider field of view antennas for critical events. They are ones directly exposed to a high temperature environment of Mercury. The remains of the telecommunication system such as a transponder and a power amplifier were selected from the heritage of our past deep space missions. These instruments are placed inside MMO where a milder environment is expected than the outside. The total telecommunication system has been designed so that it should work through the MMO mission lifetime from the launch in 2016 to the end of the mission in 2025 including an extra year of extension. The system has experienced thermal environmental tests and proved its excellent resistivity to predicted environments. We will discuss these technologies incorporated in MMO and her telecommunication system design.