Since arriving at Mars in October 2016, the ExoMars Trace Gas Orbiter has been aerobraking its way into a close orbit of the Red Planet by using the top of the atmosphere to create drag and slow down. It is almost in the right orbit to begin observations – only a few hundred kilometres to go.
With aerobraking complete, additional manoeuvres will bring the craft into a near-circular two-hour orbit, about 400 km above the planet, by the end of April. The science instruments will be tested for several months from the new orbit.
The mission’s main goal is to take a detailed inventory of the atmosphere, sniffing out gases like methane, which may be an indicator of active geological or biological activity. The camera will help to identify surface features that may be related to gas emissions.
The spacecraft will also look for water-ice hidden below the surface, which could influence the choice of landing sites for future exploration. It will also relay large volumes of science data from NASA’s rovers on the surface back to Earth and from the ESA–Roscosmos ExoMars rover, which is planned for launch in 2020.