Published online 12 January 2009 | Nature | doi:10.1038/news.2009.14

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Mars rover needs a date

NASA's Mars Science Laboratory needs more money to reach the launch pad, and has less time.

The Mars Science Laboratory is already over-budget and delayed.NASA

NASA's next mission to Mars has another problem — finding a launch slot.

The Mars Science Laboratory (MSL) is due to blast off in late 2011, two years later than originally planned. But so are several other missions that will require the use of an Atlas V rocket and the launchpad in Cape Canaveral, Florida.

Squeezing MSL into the schedule could require buying a more powerful rocket, reworking the lander's heat shield for faster entry speeds, and hiring more workers to cut the time between launches. All this could add US$50 million to the cost of a mission whose budget has already risen from $1.6 billion to more than $2.2 billion.

NASA's strategy for dealing with the cost overruns would not cancel or delay any other planned mission. But it would drastically cut research and development on the Mars programme and lead to a merging of planned NASA and European Mars missions in 2016. Planetary scientists endorsed the plan on Friday, when NASA officials described the scheduling issue at an advisory committee meeting.

Squeezing schedules

Weighing in at one tonne, the rover will be the largest craft ever sent to land on Mars. Armed with a battery of ten instruments, it will search for evidence of past life.

In December 2008, its original 2009 launch date was put back two years. This stemmed from problems with motors and gearboxes, which had not been tested fully for the Martian cold.

The delay meant keeping engineers on the project for longer, but it also saved money from the present fiscal year by ending months of overtime shifts at the Jet Propulsion Laboratory in Pasadena, California, where the rover is being assembled. "Frankly, in hindsight, I wish somebody had delayed this 12 months earlier," says Edward Weiler, the associate administrator of the Science Missions Directorate at NASA.

One way to deal with the schedule squeeze is to reduce the current 90-day period between launches of the Atlas V. The gap could come down to 75 days, says James Green, director of NASA's planetary science division, who has the job of dealing with MSL's busted budget and launch scheduling.

That would clear much of the late 2011 launch schedule. But one of two MSL launch windows, in October, would still be uncomfortably close to the August 2011 launch of Juno, a mission to study Jupiter's magnetic and gravitational fields.

The October window could be stretched by buying a more powerful and expensive version of the Atlas V, but that could require testing of the ability of the MSL's heat shield to withstand a speedier entry into the Martian atmosphere due to the faster rocket.

Out the window

A second launch window for MSL in December is favourable for reasons besides its distance from the Juno launch. But this would put MSL on a different route that could favour landing sites in Mars's northern hemisphere, where communications with Earth would be better.

That could re-open the debate over MSL landing sites, which had been narrowed to four, three of which are in the southern hemisphere (see Methane site ruled out on Mars). "We've got a lot of good ones, but we may want to rethink it," says NASA's Mars programme chief Doug McCuistion.

Green's plan for dealing with the cost overruns would keep the damage mostly to the Mars programme. The only major non-Mars impact would be the temporary loss from Juno's budget of $47 million in cushion money meant to cover unexpected problems, money that would become available to Juno again in 2012.

Current Mars missions, such as the Mars Exploration rovers, Spirit and Opportunity, would not be curtailed, says Green. The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission scheduled for launch in 2013 to study the history of Mars' atmosphere, would also be left alone, partly because it would be a valuable communications link for MSL. Existing orbiters, such as Odyssey and Mars Reconnaissance Orbiter, will be getting elderly by the time the MSL arrives.

Mortgaged future

But the biggest impact would be to the future of the Mars programme. A planned 2016 mission would be drastically cut. Only through partnering could it perform important science, says Weiler, who foresees future Mars exploration as being a joint European-American venture.

The European Space Agency (ESA) has already delayed its next rover, ExoMars, until 2016. Weiler says he and ESA science chief David Southwood have agreed in principle that the 2016 missions should merge.

"It was time to throw the flags away, and say, 'If we're ever going to do a Mars sample return, we're never going to do it on our own'," says Weiler, referring to a planned multi-billion mission for the 2020s. "A billion dollars doesn't buy much any more." 

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