Executioner's Song: Deciding Which Space Missions Live or Die
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Deep Impact spacecraft is expected to soldier onward after its prime mission of dispatching an impactor to strike comet Tempel 1 in July. Image Courtesy of NASA/JPL/UMD Artwork by Pat Rawlings CREDIT: |
UPDATE: Story first posted 7:15 a.m.
There has been a scientific and public backlash at the thought of shutting down spacecraft, like the vintage Voyager missions, all for the want of a few millions dollars.
But Voyager is likely to be an early signal from a growing dilemma of finding cash to keep NASA spacecraft functioning beyond their initial work period.
There are plenty of examples, like the still-going strong Mars Exploration Rovers. Also count on keeping the Hubble Space Telescope alive. Toss in an extended Cassini mission at Saturn too. Also, there's early talk about the Deep Impact flyby spacecraft possibly using its telescopic gear to scout about after it completes its main choir of hurling an impactor at comet Tempel 1 and monitoring the upshot this coming July.
But now there is growing talk of setting up something analogous to a "hit squad" at NASA that impartially agrees what projects should be ended, when, and under what rules.
Reportedly, a number of space probes could be on the chopping block, from the Ulysses mission to the Sun to several Earth-oriented space physics satellites busily sleuthing about.
Upsetting to many scientists is shutting down the long-distance Voyager -- seemingly a fit of heliospheric heresy. The valiant twin Voyager spacecraft were launched in 1977 and can define the end of the heliosphere -- the entire region of space affected by the Sun -- and the start of interstellar space.
The mission currently employs the equivalent of about 10 full-time people at the Jet Propulsion Laboratory, significantly less than the approximately 300 during the height of its legendary "Grand Tour" of the planets through 1989.
Scientific novelty
New NASA Administrator, Mike Griffin, will likely revisit a number of "pulling the plug" decisions, suggested Stamatios Krimigis, Head Emeritus of the Space Department at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.
"It's clear that in a limited resource environment, decisions and choices have to be made...none would argue with that," Krimigis said. "The key issue is the criteria used to arrive at such decisions."
Speaking at the press conference Monday following his appointment, Griffin said NASA was months away deciding which missions get terminated, and that it "would not be done without a full and careful review."
But, he added, that is not "to say that all missions are of the same importance. Voyager may well outrank others whose time to be turned off really has come. So I'm not making a blanket offer that we're going to reach a particular answer on any one mission or that we will treat them all as a block. But we are going to consider it carefully before we turn anything off."
Principal among the criteria would be the scientific productivity of a particular mission, Krimigis said.
"This is the area where the Voyager decision is totally indefensible. Why? Because Voyager has been at the fringes of the solar 'cocoon' that separates us from interstellar space for nearly three years now," Krimigis explained. Voyager has generated impressive science for so many years, and the excitement hasn't stopped, he observed.
As a principal investigator on Voyagers 1 and 2, Krimigis also serves in that role on the Cassini mission now orbiting Saturn.
The scientific novelty of this region of space is clearly intriguing not only for scientists but the public at large, Krimigis argued.
Exploration at its finest
Voyager is "exploration at its finest," Krimigis said. "NASA has no present plans for an Interstellar Probe, and even if they approved such a mission tomorrow it couldn't launch until 2014 and wouldn't catch up with Voyager for at least 15 years after that," Krimigis noted. Voyager is likely to run low on power by about 2020, he said, but could possibly continue in some reduced capacity for several years after that, doing so through power sharing and other procedures.
"It's a legacy mission that this generation can preserve for our children and even grandchildren," Krimigis stated. NASA pondering a pull-the-plug dictum on Voyager, he continued, is a decision without thought about the mission's current scientific productivity or appeal of the science to the public.
"After all, $4 million is $4 million...and to accountants all funds are the same. No wonder the scientific community has so little confidence in the decision-making at [NASA] Headquarters," Krimigis said.
Of course, not all extended missions hold the excitement of the Voyagers, but all of the ones scheduled for termination next year are scientifically productive, Krimigis said.
"I believe the return on investment for all is very high," he said, and there is no way NASA could reconstitute these assets in the next 20 years. They are the equivalent of a "Great Observatory" and must be recognized as such, Krimigis concluded.
NASA's extended family
NASA has several spacecraft they embrace as part of their "extended family".
Mars has become home to the extended orbital missions of Mars Global Surveyor and Mars Odyssey. Furthermore, those workaholic surface robots, Spirit and Opportunity, just got the go-ahead for up to 18 more months of operations - purportedly at roughly $3 million per month.
The peppy twin Mars rovers have been a surprise to engineers and scientists. They had already completed 11 months of extensions on top of their successful three-month prime missions. And what does another 18 months buy?
Pose that question to Steve Squyres of Cornell University as leader of the Mars rover science team. He's quick to answer about the value of their recently renewed Mars driving license.
"The thing that makes it so valuable is that we keep moving across the Martian countryside. If you're stuck in one place, sooner or later your science becomes nothing but routine monitoring of time-varying phenomena... like studying the atmosphere. That's important science, but it wouldn't use the rovers to anything like their full capability," Squyres told SPACE.com.
By keeping the rovers on the move, new places are always just around the bend, beyond a crater wall, or behind a sand dune.
"One thing that we've learned consistently on this mission is that our landing sites are so complex and interesting that when we go to a new place...we see new science," Squyres confirmed.
The surface of Mars is a big place. It takes a little driving around to find things, said David DesMarais of NASA's Ames Research Center. He is lead scientist of the long-term planning team in NASA's Mars Exploration Rover (MER) mission.
"The longer the mission goes, the smarter we get about Mars geology," DesMarais said. "The longer we live...we're doing a better job."
Searching for nickels everywhere
Long-lived spacecraft that receive mission extensions usually cost less to operate than during their prime time.
However, they should be made to run cheaper too, which is not always the case, said Wesley Huntress, Jr., Director of the Geophysical Laboratory at the Carnegie Institution of Washington in Washington, D.C. In a former post, he served as the chief of NASA's space science missions.
Space is populated with a large collection of older spacecraft still cranking out data, Huntress said. That being the case, the accumulative cost of running them begins to become significant, he said.
And that's what is happening now, with NASA "searching for nickels everywhere," Huntress stated. Budget pressure is omnipresent.
"It's a limited resource. You want to do new things, but you have some old things that are still productive. How do you make that tradeoff? The advocates of these missions don't have to worry about that...the folks who are writing the checks do," Huntress advised. "And so you see that battle happening."
Precipitous decisions
Huntress said he worries that NASA at its upper levels has lost the understanding that they have stakeholders. "They can't make precipitous decisions without consultation with their stakeholders. The idea of canceling Voyager, for example, seems ill conceived ...it seems to me to make very little sense," he said.
Similar in view is Sean Solomon, Director Department of Terrestrial Magnetism at the Carnegie Institution of Washington. He is principal investigator for the now en route MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission.
"One of the reasons that the Voyager discussion is so intense is because there is a potential for new science...even though this mission has been on the books now for more than 30 years," Solomon remarked. While NASA has many demands on its resources, the price tag to follow Voyager a little longer is not that great.
"On the other hand, there are many missions that are contemplating extended periods. So you probably can't do them all," Solomon pointed out. "The question is how do you decide which are the most worthy of these missions to continue to invest in?"
There are gauges for making such a determination: Health of the spacecraft's instruments; remaining fuel onboard to maintain attitude and pointing accuracy; and the originality and importance of the scientific return.
"But at some point NASA is deciding between extending a mission and flying a new mission. And that's a tougher call," Solomon said. "There is a natural tendency for active scientific groups to continue to want to see data coming in. So that's why any process of deciding on how to invest scarce dollars in extended missions should be an objective one...one in which a broader community is looking at comparisons among different kinds of missions with different kinds of objectives," he concluded.
Report card: far from stellar
The debate over the Hubble Space Telescope's longevity is a hard call, Huntress said. Essentially, both the Hubble and its follow-on, the James Webb Space Telescope (JWST) are on more or less a fixed budget.
"So the money spent on Hubble you're not going to spend on JWST. When do you make that call? That's a tough judgment," Huntress said. "And it's tougher in the case of Hubble because it is not just a telescope for scientists anymore. It has become the people's telescope."
Try turning off one of the Mars rovers today, Huntress said. "You'd get the same reaction that you're getting from Hubble. So I don't think it's peculiar to Hubble. I think it's peculiar to the way the American public takes ownership of these instruments," he noted.
During his tenure at NASA, Huntress had to put to rest the Compton Gamma Ray Observatory. Compton was safely deorbited and reentered the Earth's atmosphere on June 4, 2000.
"That one had no public consequences. That was strictly an engineering and scientific decision," he said, with gamma ray astronomers knowing that American and European follow-on missions were coming. "Compton's time had come."
Overall, NASA's report card on turning off spacecraft is far from stellar, Huntress admitted. "I think NASA prepares poorly, if at all, for extended missions...and that includes my tenure there too. We did not plan well for extended missions because we never anticipated them. But we always knew there was the potential for them," he said.
Striking the right balance
"It's something I'm wrestling with," said NASA's Alphonso Diaz, NASA's Associate Administrator for the Science Mission Directorate. "Somebody's extended mission is another person's prime mission," he told SPACE.com.
Diaz said that a senior review process done a few years ago to rank the strategic importance of missions "may or may not be relevant to the discussion today." NASA is presently engaged in strategic road-mapping, he said, with some missions perhaps having more significance now given the space agency's Moon, Mars, and beyond visionary agenda.
"I'm willing to listen...to sit down and talk about that," Diaz said. "We're currently developing a strategy to try and understand how to get to another review, one that's based on more current understanding of the significance of those missions," he said.
Reducing the cost of operating some spacecraft over a long period is on the table too, Diaz explained. Coming up with the right balance of continuing to operate extended missions versus new developments is the trade that has to be made, he said.
"It'll be a while before we have a solution," Diaz added. "We can't operate everything all the time forever."
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