ExoMars 2016, Orbiter module bus a GNC development update

ExoMars programme is part of a cooperation between ESA and Roscosmos. It foresees two missions to Mars that aim to searching for signs of past and present life on Mars, investigating the Martian atmosphere and surface and demonstrating the technologies needed to land on Mars and perform robotic exploration. The first spacecraft launched in early 2016 is composed of an Orbiter module (the Trace Gas Orbiter, TGO) carrying an entry descent and landing demonstration module (EDM) The Orbiter GNC design shall allow the spacecraft composite to cruise towards Mars, to accurately release the EDM, to make orbit insertion in Mars orbit with chemical propulsion system, to circularise the orbit by aerobraking and perform atmosphere observation with the four payloads instruments while relaying communication from assets on Mars surface. After a brief presentation of the ExoMars mission and constraints, the paper first provides an overview of the TGO GNC design (in term of mode and sensor/actuator), then an updated status of development is given. A special emphasis is given to the GNC level implementation of the aerobraking strategies and on specific FDIR features.