Science & Astronomy
15. March 2016

Yeserday, the first Mars mission to touch down on the red planet since Curiosity in 2012 has launched. The joint ESA and Roscosmos ExoMars Trace Gas Orbiter with its Schiaparelli lander is actually only the beginning of a two-part mission that will have a sequel in 2018 with the ExoMars Rover. So why is this so exciting? Originally, ExoMars was supposed to be a combined ESA and NASA mission before the US cancelled it for budget reasons in 2012. ESA saw this coming in late 2011 and had already talked to Roscosmos for a possible collaboration before the bad news actually came and fortunately the project was able to go ahead with Roscosmos as the new partner. ExoMars is really the Mars mission that almost did not happen! I don’t usually write articles like this one much anymore, but I’m making an exception because I’ve written about almost every Mars mission before and I just want to continue that. 

This first part of ExoMars that successfully launched yesterday will arrive at Mars on October 19 and then send the Schiaparelli lander, which actually separates from the orbiter three days before arrival, for a touchdown to the planet. This is something that neither ESA nor Roscosmos have successfully done before – while Mars 3 and Beagle 2 were the only probes to actually make a soft landing, they never properly worked on the surface. Maybe because of the huge failure rates of the European and Russian Mars landers, ExoMars was planned with two surface missions from the start – first a demonstration lander and later a full rover. The Schiaparelli EDM (Entry, Descent and Landing Demonstrator Module) will do exactly that – it is more or less a meterological station with an thermometer, barometer and hygrometer and also instruments to measure wind speed, atmospheric radiation and electricity plus an optical dust sensor.

Although Schiaparelli has no surface camera, it does have descent camera which will be used together with a second science package that collects data during the descent through the atmosphere. A special feature of Schiaparelli is also that it carries a reflector, allowing orbiting spacecraft to locate it with the help of lasers – a first for a Mars lander. The landing site will be at the Meridiani Planum – in the neighbourhood of the Opportunity Rover, which may possibly get a glimpse of Schiaparelli when it arrives. Unfortunately, Schiaparelli will only have a lifetime of a couple of days because it has non-rechargeable batteries – Roscosmos had originally planned to supply the lander with an RTG, but this was supposedly cancelled because of export issues and solar panels were deemed to expensive for a demonstration lander.

The lander sounds exciting, but the ExoMars Trace Gas Orbiter is actually the main part of the mission that continues to operate long after its lander will stop wprking Its purpose is, basically, to look for gases in Mars’ atmosphere that could be indicators for life – it was originally called the Mars Methane Orbiter during its first incarnation at NASA in the late 2000s and has since then evolved into an even more sophisticated science instrument. It will be able to locate and pinpoint the source of many atmospheric trace gases with the help of two different instrument groups developed in Belgium and Russia and it also has a Russian neutron detector, which can detect surface hydrogen. The orbiter also carries a high-resolution stereo camera build in Switzerland that will map the planet and look for a spot to land the 2018 Rover.

Even though it has been named Trace Gas Orbiter or TGO, it will also double as a fully equipped communications relay with the same module that is also working on MRO and MAVEN, which will expand the group of the Mars communications network necessary to support the ground missions. The ExoMars TGO orbiter will be in service at least until 2022, if not longer – the first mission is to support the lander, but after that the orbiter has to perform a series of aerobraking maneuvers to get it into its 400×400 km circular orbit, which will take all through 2017. This is why the primary science mission is only slated to begin at the end of 2017.

As for the future of the second ExoMars mission coming in 2018, there are some reports that it might be delayed until 2020 because the schedule for completing the hardware seems too tight – and financial reasons have also been mentioned. Right now it’s too early to say what might happen, but ExoMars is certainly no stranger to delays or cancellations. With launch windows opening up only every two years, it might be 2020 or even 2022, but hopefully not so late as to miss the lifespan of the orbiter.

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