WASHINGTON — Embarking on what both sides are hailing as the start of a sustained team effort to explore Mars, NASA and the European Space Agency (ESA) intend to lay the foundation for a long-desired mission to retrieve rock and soil samples from the red planet by launching a science orbiter in 2016 that will double as a communications relay for future landers.
But the cooperative strategy for exploring the red planet comes at the price of NASA’s Mars Scout series of missions, which will be discontinued after the Mars Atmosphere and Volatile Evolution (MAVEN) mission, now slated to launch in 2013.
The 2016 mission, which began coming together after NASA and the 18-nation ESA agreed last year to pursue a joint Mars exploration program, reached a key milestone Aug. 2 with the announcement of the five instruments that will comprise the orbiter’s scientific payload.
Four of the instruments will be built in the United States and paid for by NASA, which also will contribute communications components and launch the probe aboard a U.S. Air Force Atlas 5 rocket. ESA will supply the platform for the ExoMars Trace Gas Orbiter and also contribute a small, short-lived lander designed to test an all-European entry, descent and landing system.
A fifth selected instrument, a spectrometer proposed by a Belgian scientist, will be built in Europe. But even that instrument will have U.S. participation.
“ESA is leading the mission, but we actually have the science lead for 2016,” Michael Meyer, lead scientist for NASA’s Mars Exploration Program, said in an Aug. 4 interview.
Meyer said NASA expects to spend “a little over $100 million” on the instruments.
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As recently as last summer, when ESA was still hoping to launch the billion-dollar ExoMars rover and lander in 2016, NASA envisioned contributing a U.S.-built science orbiter, not just a suite of instruments.
“It just would not work,” Meyer said. “We tried and tried and tried and just finally said there’s no way we can do a full-size ExoMars lander and do an orbiter that will do a decent amount of science.”
Money was one factor; physics was another.
Because of the way Earth and Mars align as they orbit the sun, “2016 is the tougher opportunity. 2018 is a really great opportunity in terms of the energetics of being able to put something on the surface,” James Green, director of NASA’s Planetary Science Division, said in an interview.
The 2016 launch opportunity — favorable Mars launch windows occur roughly every 26 months — also has a higher probability of strong dust storms that would further complicate a large lander mission, Green said.
In place of a heavily instrumented science rover, ESA will build a small, battery-powered lander expected to survive just a few days after touching down. ESA has never carried out a Mars lander mission.
In addition to carrying a suite of instruments intended to study the chemical makeup of the martian atmosphere with a thousand times the sensitivity of previous Mars orbiters, the ExoMars Trace Gas Orbiter will serve as a communications relay for the pair of orbiters NASA and ESA plan to send to Mars in 2018 as the vanguard for a sample-return mission the partners hope to launch in 2020 or 2022.
The 2018 mission, Green and Meyer said, also will launch on an Atlas 5, but the more favorable planetary alignment then will permit both NASA and ESA to send along substantial rovers.
ESA’s rover will include a drilling capability while NASA’s rover will be equipped to quarantine rock and soil samples for potential future return to Earth. Both rovers, Green and Meyer said, will use the same entry, descent and landing system NASA will use for the first time on the Mars Science Laboratory mission slated to launch in November 2011.
Meyer said NASA hopes to use the landing system, which uses a winch to lower the rover from a hovering platform, for the sample return mission as well.
NASA has been studying Mars sample-return concepts in earnest since the 1990s. But funding for such a challenging and expensive undertaking has never materialized; the mission keeps “going over the budget horizon,” Meyer said.
“This is the first time where I’m actually confident that we can do a sample return,” Meyer said. “We’ve split it up so it’s manageable. We’ve actually overcome many of the engineering hurdles, such as how we get a metric ton to the surface of Mars. We will have had a rover that knows how to handle samples.”
By spreading key parts of the project across different missions — using the 2016 orbiter as a communications relay and collecting samples in 2018, for example — and sharing the tab, NASA and ESA can bring Mars sample return within the realm of affordability.
“We don’t have to have a budget miracle happening sometime in the future to get us to actually do sample return,” Meyer said.
But Meyer and Green acknowledge there is more technology development to be done before NASA and ESA set out to retrieve samples from Mars. One of the technological long poles, they said, is the vehicle that will lift off from the martian surface to help bring samples back to Earth. “We’re starting kind of slow,” Green said. “We’ve had [a request for information] … asking industry for ideas on what the [Mars ascent vehicle] should be like [and] there will be some funding in that area to look at what would be the best approach.”
That funding, Green said, would first show up in NASA’s 2012 or 2013 budget request.
To afford the new plan, NASA’s Mars Exploration Program will end the line of competitively selected, scientist-led Scout missions that sent the Phoenix lander to Mars in 2007 and is set to launch the MAVEN orbiter in 2013.
“Looking at our budgets, we can’t do everything,” Green said. “So it’s not possible for us to keep the Scout line going … as originally planned and work with ESA and take advantage of every [Mars launch] opportunity.”
While the Scout program will be discontinued, Green said scientists will still have the opportunity every few years to propose Mars missions for NASA funding.
“[W]e’ve come up with a fabulous alternate in terms of opportunities and that is bringing the Mars opportunity back into the Discovery line,” Green said, referring to the NASA program currently soliciting proposals for scientist-led planetary missions that could be ready to launch by the end of 2017.
“The cost cap is $425 million and that does not include launch vehicles,” Green said. “That’s very comparable to what the Mars Scout would be so it’s a viable opportunity.”
NASA’s 2011 budget proposal, now before Congress, includes nearly $533 million for Mars exploration next year, a 28 percent increase that reflects the completion of the assembly, testing and launch of the $2.5 billion Mars Science Laboratory and the start of full-scale development of the MAVEN mission.
Under current NASA projections, Mars spending would average $530 million annually through 2015.
