ExoMars: Long day’s journey into uncertainty

The European Space Agency has been “managing expectations” all day. It’s a euphemism every business employs for preparing people not to get what they wanted. “Underpromise and overdeliver” is also a popular phrase at ESA. But sometimes you must state your ambitions publicly, and the orbital insertion of the ExoMars Trace Gas Orbiter (TGO) and landing of the demonstration lander Schiaparelli was such a time. Recent NASA successes on Mars may have yielded the impression that landing there is easy. ESA have been underlining that it is not, nor has it been easy for their partners, Roscosmos.

First, the good news. The main part of the mission, the Trace Gas Orbiter, has been inserted into the correct orbit. It will look at the gases constituting less than 1% of the atmosphere, focusing especially on methane. ESA’s Mars Express has detected methane from orbit already, and Curiosity has seen it come and go from the surface. Its transient nature has puzzled planetary scientists. It shouldn’t persist in the atmosphere, implying that somehow it is being replenished by geological or biological processes undefined; nor should it vanish so quickly after it appears.

TGO’s safe arrival promises that the main science mission can proceed, and it will begin an aerobraking phase to change the shape of its orbit to a circular, science one in January. Once fully settled in, it will also become a relay point for NASA landers, fulfilling two of the three main objectives of ExoMars 2016.

The third objective was to demonstrate that Europe can land on Mars. On that front, the news is less positive. Both the data from Giant Metrewave Radio Telescope in Pune, India, and the data from Mars Express indicate a loss of signal at the same stage of the descent of the lander.

“That’s the bad news,” says Paolo Ferri, head of mission operations at ESA, “The fact that Pune and Mars Express lose the signal at the same time before the predicted time of touchdown.

“We will hear if there is some information from MRO [Mars Reconnaissance Orbiter] –but frankly I consider it unlikely that we get data from MRO. If we lost the signal before the landing, at least with the communications, why should MRO be able to communicate automatically?”

With no information coming from the lander, the key question is whether the lander itself is lost, or whether it’s just not able to communicate. There is more information about Schiaparelli’s fate on the way, with raw data expected around midnight Darmstadt time.

“TGO has been recording telemetry – it has recorded more than 20MB of data,” says Ferri. “TGO was doing a more important job, which was to get in orbit. So it was in a mode that doesn’t allow it to dump data.”

Switching into that mode, and sending back the data will take several hours.

“The estimation is that by midnight we should have the data here. Then these data have to be processed. It takes some time – it is a sampling of the radio signal. I’m pretty confident that this data – this telemetry – will tell us what action was interrupted when we lost the communication. I think, I am quite optimistic, that tomorrow morning with this data, we will know what happened,” Ferri says.

“It may mean we have some hope and some strategies to re-establish communication – I’m just speculating now. But we have very good chances to know tomorrow morning either to know that the lander is lost or to know the strategy to try to recover communication.”

If the lander is lost, so are the descent pictures it would have sent from the surface. As would be the final objective of the mission, the science that Schiaparelli would have been able to conduct during its time there – albeit a mission that was limited by battery life. If the lander is not transmitting, its battery life may be extended slightly, but its days are still very much numbered.

“Of course we hope we have a problem with the communications and not with the landing sequence. Certainly the problem happened very late in the sequence – there is a good chance that the parachute phase worked but at the moment we don’t know, it’s all speculation,”Ferri says.

The test of landing technologies was key to the next part of ExoMars – the 2020 lander and rover. But ESA so far are remaining optimistic about the future of the next mission.

“We need to learn how to land on Mars,” says Ferri, “And for me, whatever we understand of what happened, of course it helps to get to that objective.

“Whether we achieve it 100%, 95%, 90%, or 0%, but zero I think we can already exclude. The sequence was very long. But how far we have gone, I can’t say. I am pretty confident that we have enough data to do that.”

ESA Director General Jan Wörner sustained hope for the lander, and confidence in its contribution to the 2020 mission saying: “It is a big success for ESA – to fly to Mars is a very big challenge, to be in the orbit of Mars is a very big challenge.

“This spacecraft is a marvellous feat of engineering. Of course we also look at this part [Schiaparelli] this is a test part. We don’t know all the details but this is typical of a test. We did this to learn about how – using European technology – to land on Mars.”

“Our experts will look how to manage the next landing when we will go with the rover. I don’t close my hope right now that everything is fine.”

The next communication from ESA is expected at a news conference at 1000 CEST (0800 UTC, 04:00 EDT, 01:00 PDT) on Thursday. The most talented and experienced people on the mission have a long night ahead of them following their long day.