Turning ISS into a full-fledged space laboratoryby Jeff Foust
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| “We waited for 15 years—actually, 18 years—to write this paper,” Ting said of the first AMS results, to be submitted within weeks. |
To date, though, the station hasn’t fully realized that potential for research. For many years, the explanation was that the station was still being assembled—it is, after all, hard to do work in a lab when you’re still building it. However, the ISS is now complete, and the clock is ticking on the ability of scientists to make use of it before the end of the decade, when NASA and its partners will have to make a decision on whether to extend the station’s life beyond 2020. Fortunately for station advocates, the first breakthrough results from research on the station may be just around the corner.
AMS and the search for dark matter
The biggest single experiment, in terms of both size and cost, on the ISS is the Alpha Magnetic Spectrometer (officially designated AMS-02 to differentiate it from a prototype, AMS-01, flown on the STS-91 shuttle mission in 1998, but usually simply called AMS.) Weighing nearly 7,000 kilograms and costing an estimated $1.5 billion to develop, NASA installed AMS on the exterior of the ISS on the penultimate shuttle mission, STS-134, in May 2011 (see “The space station’s billion-dollar physics experiment”, The Space Review, May 16, 2011).
Since the launch of AMS, though, the project has been relatively quiet about the data collected and its analysis, beyond updates on the number of particles detected. “Today, we reached 29,000,000,000 particles measured,” the AMS team announced on its Twitter feed on February 14. The first science based on the analysis of some of those 29 billion particles is coming soon, though.
At a press conference February 17 during the annual meeting of the American Association for the Advancement of Science (AAAS) in Boston, Samuel Ting, the MIT physicist who is the principal investigator for AMS, said his team was working on a paper analyzing a subset of the AMS data involving detections of high-energy electrons and positrons. “We waited for 15 years—actually, 18 years—to write this paper,” he said. “We have finished the paper and are now making the final checks.” He said he anticipated that the paper would be completed and submitted to a journal (as yet undecided, although Ting said later one possibility is Physical Review Letters) in two to three weeks.
While Ting didn’t disclose any of the results that will be in that paper, he did discuss what the paper would cover. It will examine the ratio of positrons to electrons as a function of energy from 0.5 to 350 billion electron volts. (The AMS can detect particles up to a trillion electron volts, but Ting said they didn’t yet have a statistically significant sample of data at the higher energies.) It will also measure changes in the ratio as a function of direction to see if its distribution is the same in all directions or has peaks in a particular direction, such as towards the center of the galaxy.
Changes in that positron/electron ratio as a function of energy, including increases or sharp drops, could provide evidence for one candidate of dark matter known as weakly interacting massive particles, or WIMPs. Dark matter comprises about 23 percent of the universe, but its influence has only been detected indirectly, such as the rotation curves of galaxies. Scientists hypothesize that if dark matter is made of WIMPS—in particular, a particle known as a supersymmetric neutralino—it will produce antimatter particles like positrons when it collides with each other, creating a signature in the data detected by AMS.
Despite repeated prodding by journalists, Ting declined to disclose any details about the results prior to submitting that paper, although he wasn’t above dropping a hint or two about at least the significance of the results. “Certainly we’re not going to publish something if it’s not worthwhile,” he said at the press conference.
| “What we want to do is try to do the best we can, because I suspect in the next 10 to 20 years nobody will be foolish enough to put another magnetic detector in deep space given the non-technical difficulties we had to put this in space,” Ting said. |
If the AMS data does provide evidence of the existence of WIMPs, it would be a major breakthrough for cosmology. “Figuring out dark matter is at the top of the wish lists of both particle physicists and cosmologists,” said Michael Turner of the University of Chicago at the same AAAS press conference. The AMS, along with efforts by ground-based detectors and CERN’s Large Hadron Collider, promise to either find evidence for the WIMP or send theorists back to their chalkboards. “We believe that this will be the decade of the WIMP.”
Ting, though, didn’t feel any rush to get the AMS results on the positron/electron ratio published, instead taking a slow, methodical approach to ensure the data were as accurate as possible, with six groups separately analyzing the data. “What we want to do is try to do the best we can, because I suspect in the next 10 to 20 years nobody will be foolish enough to put another magnetic detector in deep space given the non-technical difficulties we had to put this in space. What we want to do is do it very, very accurately.”
Taking the g out of the equation
AMS, though, is something of an outlier when it comes to ISS research. It’s a standalone module mounted on the station’s exterior, using the station primarily as a spacecraft bus, supplying power and data. The experiment doesn’t require the station’s crew to take any action; Ting said at the AAAS meeting that the experiment could continue to function if the crew had to leave the station for some reason (provided, presumably, the station was still functional enough to keep supplying AMS with power and data links.)
Other research on the ISS is starting to produce results as well, if not immediately as groundbreaking as the AMS. “Now that we’re a little over a year past the completion of assembly, we’re starting to see that scientific research come into full flower,” said Julie Robinson, NASA’s chief scientist for the ISS, at a session about space station research at the AAAS meeting. “We have not been able to benchmark any other national laboratory or international laboratory that serves so many disciplines simultaneously.”
That conference session provided a sampling of the type of research taking place at the station, including Ting talking about the AMS but also others doing research in biotech, material science, and space medicine. The purpose was to demonstrate the research that can, and is, being done on the station.
“It’s valuable in understanding every element of life and physical sciences,” said Elizabeth Cantwell of Lawrence Livermore National Laboratory, who co-chaired the latest decadal survey of biological and physical sciences in space, published in 2011. “It’s the closest analog environment for long-term deep space human exploration.”
“There were certainly people who were saying, ‘Do you really need this great big laboratory?’” recalled Michael Barratt, a physician and astronaut who spent more than six months on the ISS in 2009 as a member of the Expedition 19 and 20 crews. Skeptics, he said, wondered if the ISS was really needed to learn how the human body adapts to the space environment before mounting expeditions to the Moon or near Earth asteroids.
| “Now that we’re a little over a year past the completion of assembly, we’re starting to see that scientific research come into full flower,” said NASA’s Robinson. |
Barratt, who now manages the human research program at NASA’s Johnson Space Center, argued based both on research and his own experience that the station is key to a better understanding of how humans handle extended exposure to microgravity. “What station gives us, from my standpoint as a practitioner of clinical space medicine, is that it is a big, well-equipped laboratory.”
Research on the ISS, he said, has helped develop nutrition and exercise countermeasures to reduce the rate of bone loss previously experienced by long-duration crews, an issue that raised questions about the ability of people to be in suitable condition after a long-duration flight to, for example, land on Mars. “We’re seeing insignificant changes in bone density” in critical regions like the pelvis, he said, as well as an increase in lean body mass percentage. “We could have only accommodated this on station” given the requirements of the research, he said, including the exercise equipment required.
The ISS research is turning up new human health issues, though. Recent studies have shown evidence of vision changes in astronauts causing by changes in intracranial pressure in the eyeball. “It’s probably the most significant discovery we’ve made in space physiology in 20 years,” he said. There was evidence of vision issues going back to the shuttle program, but it wasn’t understood until it was studied in greater detail on the ISS, including Barratt himself, who experienced those vision changes during his time on the station.
“We don’t know what the clinical implications of it are, but we know we need to find this out,” he said. “It’s something that’s a big focus of our research attention right now.”
Research involving astronauts inside the ISS isn’t limited to space medicine, though. Mark Weislogel of Portland State University described some of the work he’s done to study capillary fluid flows in microgravity, including how to design propellant tanks and plumbing systems that take advantage of these conditions to provide flows without the need the need of thruster firings or other mechanisms. One demonstration of this was a zero-g “coffee cup” that Don Pettit drank from during a stay on the ISS a few years ago.
Having the astronauts perform research and be in direct contact with researchers is also a benefit that goes beyond the science itself. “Students are getting the opportunity to talk with the astronauts” as they carry out the experiments, Weislogel said. “That’s an impact on the students, and a bigger impact on the prospective students, and a big impact on the school.”
Working on the ISS has its challenges as well. “As a life scientist doing biomedical research, you cannot make a living doing research on microgravity platforms,” said Cheryl Nickerson of Arizona State University, who has done research on the ISS and shuttle flights to study infectious diseases, such as salmonella. “There is not routine and consistent funding for the platform, and there is not routine and consistent access to the platform.”
| “We’ve got a finite window with the space station over these next several years to prove that research in space provides real, tangible benefits,” Gerstenmaier said. |
Asked later about the access issue, Nickerson explained that ISS researchers don’t yet have the same level of availability they’re used to with terrestrial labs. “When you’re in your lab doing experiments 24/7, that’s the way a real lab works,” she said. “We need much better and much more routine access, but that does not at all negate the tremendous potential value of the platform to provide this kind of novel insight, and hopefully in the future we’ll have that kind of access.”
“The limitation on access, I think, has a lot more to due with the funding for life sciences research,” Robinson said, noting limited funding with NASA for such research in the recent past. “That’s the challenge that our CASIS colleagues are also encountering” as they talk about the prospects for ISS research with commercial partners, she added.
CASIS, or the Center for the Advancement of Science in Space, is the non-profit organization selected by NASA in 2011 to manage research on the portion of the station designated a US National Laboratory. After a slow start, CASIS has been ramping up its efforts, with a booth at the AAAS meeting exhibit hall and advertising in publications outside the traditional space industry, such as Fast Company, a magazine that targets more entrepreneurial audiences. The full-page ad contrasted a person looking out the window of a typical office (“Your office window.”) with an astronaut peering out of the ISS cupola (“Our office window.”) “With dramatically less of an investment than you think,” the ad claimed, “your company’s research could be conducted in the unique environment of the International Space Station.”
NASA associate administrator Bill Gerstenmaier is optimistic that other researchers will take advantage of the facilities on the ISS in the coming years. “I would argue that any process that has a ‘g’ in its basic equation,” he said in a speech at the FAA Commercial Space Transportation conference in Washington earlier this month, “and you remove that g, you get a different way to at that same physical property. If that can be shown to provide a competitive advantage, that can potentially spur a new market in space.”
Creating that new market could be essential to the long-term future of the ISS, demonstrating it has capabilities worthwhile enough to keep the station operating beyond 2020, the current date the partner nations have agreed to support the ISS. “We’ve got a finite window with the space station over these next several years to prove that research in space provides real, tangible benefits,” he said (see “Asking the big questions for the next ten years”, The Space Review, February 11, 2013).
Even relatively hands-off experiments like AMS, though, have its challenges. “I did not realize how difficult it is to work on the space station,” Ting said. One challenge is to keep the experiment’s temperature constant to within one degree Celsius throughout the frequent day-night cycles and changing thermal environment around the station. A control room for AMS, at CERN in Switzerland, is staffed by up to a dozen people around the clock to monitor the experiment.
But in a few weeks, the AMS may offer scientists a major advance in their understanding of dark matter and the nature of the universe—the beginning of what NASA and other station partners hope is a wave of research breakthroughs that will be sustained through the end of the decade and perhaps beyond.