With less-frequent selections, proposers worry about rising costs and complexity.
In space exploration, ambitious goals invariably demand time and money. NASA’s Discovery Program, which in the coming days will award US$425 million to one of three missions competing to send a probe to Mars, a comet or Saturn’s moon Titan (see ‘The final three’), is no exception.
The programme, though, has always aimed to deliver big science at relatively low cost, and its craft have explored almost every corner of the Solar System since the first probe launched in 1996. Discovery-class launches initially came every year or two — but now the tempo is slowing. The new mission will be the first to be chosen in five years, and there will be a similar wait for the next one.
The growing lag — and the escalating costs and complexity that have caused it — is having a deleterious effect on the programme, some NASA observers say, because it creates an increasingly risk-averse approach to mission selection. “The real threat to Discovery is that it is slowing down,” says Alan Stern, a planetary scientist at Southwest Research Institute in Boulder, Colorado, and former associate administrator for science at NASA.
David Bearden, general manager for NASA programmes at the Aerospace Corporation of El Segundo, California, is not surprised by the trend (see ‘Mission creep’). Budget pressures have limited the frequency of larger, more expensive flagship missions such as the $2.5-billion Mars Science Laboratory, which is due to land on the red planet next month. So planetary scientists have looked to the regular Discovery launches to provide more of the data they crave, and pushed to add scientific instruments to the probes. The Near Earth Asteroid Rendezvous (NEAR), the first Discovery mission, sent five instruments on a relatively simple mission to the asteroid Eros. By contrast, MESSENGER, a 2004 mission to Mercury, had seven instruments and had to follow a complicated path to get to the planet. It ultimately ran 43% over its intended budget.
Stern says the lag in launches drives up not only the costs associated with technological complexity, but also the expense of management. Managers must keep engineering teams around for longer, and, with the stakes raised, end up spending extra money on tests and verifications. “When your launches are less frequent, each one matters more,” he says. “That becomes its own psychological driver for costs for project and programme managers.”
All of this is why Gregg Vane, the programme manager for mission formulation at NASA’s Jet Propulsion Laboratory in Pasadena, California, says that Discovery has strayed from its original intended purpose, which was to be a riskier counterpoint to the too-big-to-fail flagships. Failure is no longer an option for a Discovery mission either, he says. “The tolerance for risk is significantly lower than it has been in the past.”
However, Jim Green, director of NASA’s planetary-science division, flatly denies this charge. “What is it about those [missions] that you think is averting risk?” he asked. “You can’t tell me that the missions we’ve executed in Discovery are not pushing the envelope.”
Nevertheless, avoiding risk was key when Vane and his colleagues prepared their plans for the proposed Mars mission, InSight, which would put just two instruments on a spacecraft design that has been used successfully in a previous Mars mission. Caution, he believes, will also be uppermost in the minds of the review-committee members. “It’s all about risk,” he says. “Period.”