ExoMars Rover

News Analysis: The Red Planet still beckons the world's space scientists

Mark Williamson examines plans to explore Mars in an era of budgetary constraint.

We live in a vicarious world, where the ‘like’, ‘share’ and ‘follow’ of social media often replaces personal experience. While arguably detrimental to our general wellbeing, this fits right in with space exploration, because it allows the engagement of an audience that has no other option.Nasa made full use of social media for the landing of its Curiosity rover on Mars this August, chalking up a space mission record of 3.7 million views on YouTube. According to Veronica McGregor, Nasa’s social media manager, Curiosity’s Facebook page had 30,000 ‘likes’ before the landing, but had reached 400,000 by early October, while its Twitter followers increased from 120,000 to 1.2 million.

Whether or not this impresses you will depend on your general predilection towards social media, but in a budgetary environment that precludes manned spaceflight beyond low-Earth orbiting space stations, it’s the closest any of us will get to Mars for the next few decades at least.

The continuing success of the Curiosity mission made Mars exploration a key topic at the 63rd International Astronautical Congress (IAC), held in Naples, Italy, at the beginning of October. Several presentations focused on the innovative Skycrane, a rocket-powered descent vehicle designed to hover over the landing site and lower the rover gently to the surface, before flying off to bury itself in the red dirt some distance from Bradbury Landing (named after the recently deceased science fiction author Ray Bradbury).

Miguel San Martin, head of guidance, navigation and control (GNC) for the Mars Science Laboratory (MSL), understands why many in the science and engineering community considered Skycrane to be science fiction, but he explained its foundations in detailed engineering analysis. Effectively, he said, Skycrane was an updated Viking soft lander (two of which reached Mars in the mid-1970s) with a one-ton rover strung beneath it. The idea came from the truck-transporting helicopter of the same name developed by Sikorsky in the 1960s.

For MSL, Skycrane was the only practical way to get such a heavy rover to the surface at a survivable touchdown velocity of less than 0.75m/s. It offered the additional advantage of delivery to a rough surface, because it was Curiosity’s six articulated wheels that performed the touchdown.

The GNC computer that controlled the final descent and landing is on the rover, not Skycrane, which saves weight by not duplicating computer systems. While Curiosity needs a computer for the whole of its two-year life on Mars, Skycrane would only need one for a period the Nasa publicity machine called the “seven minutes of terror”. Following Curiosity’s touchdown, all Skycrane had to do was reel in the tethers and, firing its engines to propellant depletion, clear the area on a pre-planned heading (with minimal processing capacity).

Successful though the landing was - especially considering the difficulties in testing such a system - the touchdown velocity was higher than expected, according to San Martin. “A gravitational anomaly in Gale Crater was only discovered by the lander,” he revealed. “I guess it added about a tenth of a metre per second to the touchdown speed.” Such is the level of accuracy involved in a landing!

Although Nasa’s success with MSL has been lauded throughout the media and the space profession, it doesn’t take much digging to reveal disquiet regarding that mainstay of modern-day space exploration: international cooperation.

Much of this relates to Nasa’s effective withdrawal, in 2011, from the European Space Agency’s ExoMars programme; for budgetary reasons, its contribution is currently limited to a minor payload. When Nasa reneged on its promise to provide the launch vehicle, ESA had to redesign its mission and negotiate the assistance of the Russian space agency in providing a ride to Mars. While Europe has the technical capability to deliver ExoMars using its Ariane 5 launcher, this would have increased the programme budget well beyond what ESA Member States were willing to pay.

During an IAC press launch, Luigi Pasquali, CEO for Thales Alenia Space Italia, admitted that ExoMars had been “a tough programme”, but confirmed that now the risks are managed and the programme is on schedule. “We expect no surprises, even from Moscow,” he added.

ExoMars project manager Vincenzo Giorgio explained that it now comprises a 2016 mission and a 2018 mission, reflecting the fact that viable launch windows for Mars open approximately every two years. The first will include the Trace Gas Orbiter, carrying an entry and descent module, or ‘lander’, which will make observations from the surface. The second is designed to land a rover on Mars. Russia will contribute the descent module and launch vehicles, while ESA is responsible for the rest.

The underlying message in all of this is that Europe can pretty much do what Nasa does, without its assistance if necessary. The difference, arguably, is the scale of the mission and the size of the rover. MSL, with its Skycrane and car-sized rover, was a $2.5bn mission, according to Giorgio, who said: “We can’t afford that!”

Keen to justify Nasa’s stance and make a political point, Nasa administrator Charles Bolden made much of international cooperation at the annual Heads of Agencies Plenary. “The most important thing about Curiosity,” he declared, “is that it’s an international venture [including] Spanish, British, Russian and Canadian contributions.” The rover carries two rad-hard processors from BAE Systems and an X-ray spectrometer from the Canadian Space Agency.

This collaboration apart, it seems strange that, having pulled out of ExoMars for financial reasons, Nasa has been able to announce a new Mars lander for 2016. Among other things, the $425m InSight mission’s lander will probe beneath the surface in an attempt to characterise the planet’s seismology for the first time. Although it will carry instruments from France and Germany, InSight fails to qualify as ‘international cooperation’ at the agency level. ESA must be gritting its metaphorical teeth.

Meanwhile, according to San Martin, Nasa is looking forward to using its Skycrane technology for future missions and estimates that a landed mass of up to 1.5 tonnes could be accommodated. Nasa’s Mars Program Planning Group (MPPG), tasked with evaluating options for the 2018-2024 windows, has just come up with four possible concepts for rovers and orbiters. Although its Mars Next Decade missions will not be announced until February, Nasa’s lead scientist for Mars exploration, Michael Meyer, has already labelled sample return as “the primary goal for Mars exploration”.

No doubt wary of predictions and promises, Bolden has urged Nasa’s international partners not to read too much into the MPPG report, saying “Nasa does not plan to do anything alone” in Mars exploration, and leaving the door open for collaboration. The fact is, Bolden can’t predict Nasa’s budget and the expectation is that help from partners will be needed to get those Mars rocks back to Earth.

At this rate, it is hard to see how Nasa can meet President Obama’s political goal of a manned Mars mission by 2030. Nevertheless, despite the global financial crises, space agencies are still demonstrably keen to explore Mars using unmanned spacecraft. *

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