Scientist Dan Reisenfeld has involved UM in multiple NASA space probe missions, which have studied everything from Saturn and mapping the edge of the solar system to the composition of the sun.
Researchers help NASA reveal secrets of the solar system
By Cary Shimek
It was early afternoon in autumn semester 2009 when Dan Reisenfeld jumped up before a class he was teaching at The University of Montana and exclaimed, “There’s nitrogen coming off of Rhea!”
The 10 students taking Quantum Mechanics stared at him slack-jawed. You could have heard crickets.
“They gave me a look like, ‘What have you been smoking?’” says the assistant professor in UM’s Department of Physics and Astronomy. “They were rather bemused by my excitement, but then they wound up asking lots of questions.”
For those who aren’t astronomy buffs, Rhea is the second-largest of 62 known moons circling Saturn. NASA has an unmanned space probe called Cassini orbiting Saturn, studying wonders such as the intricate system of ice-particle rings and smog-shrouded Titan, the only moon known to have a dense atmosphere. Cassini, and the Huygens probe it sent to Titan’s surface, revealed vast methane lakes and wind-sculpted hydrocarbon sand dunes hidden beneath the clouds.
Cassini also detected polar water geysers venting off the Saturnian moon Enceladus back in 2006. Reisenfeld was part of the team that made that discovery, as his research group helps analyze the raw data streamed to Earth from Cassini.
“A lot of these moons circling high-gravity planets like Jupiter and Saturn get their innards churned by tidal forces,” he says. “This churning kind of grinds them up inside, generating heat and giving rise to geysers, volcanoes and such.”
So back in 2009, while staring at the computer monitor in his campus office to analyze data sent from Saturn, Reisenfeld suddenly made a realization that sent chills cascading through his body. The Cassini data revealed a large nitrogen source emitted from Rhea.
Why does the moon have a nitrogen source? Why is it nitrogen and not water like Enceladus? Why was it so different?
Scientists still don’t know the answers. Reisenfeld’s discovery had just revealed a new set of mysteries to explore. But at that time he knew just one thing: He couldn’t wait to tell his students.
Reisenfeld first visited Yellowstone National Park with his parents when he was 11 months old, and much of his life thereafter was spent trying to return to the West. He grew up loving science and watching “Star Trek” in Cincinnati, and he went on to study physics at Yale and astronomy at Harvard. He considered attending graduate school in Boulder, Colo., but noticed most of the professors there were from places such as Stanford, Berkeley or Harvard. He realized he needed similar credentials to choose where he would work, so he deferred his westward momentum to study back East.
His initial move west came in 1998, when the astrophysicist landed a postdoctoral and then a staff scientist position at Los Alamos National Laboratory in New Mexico, a hotbed for NASA science missions and spacecraft design. He became involved with numerous space probe projects and found time to meet and marry Maureen, a hydrologist. Reisenfeld loved his job, but he also missed teaching, which he had done at Harvard and the University of New Mexico. So in 2004 he accepted a faculty position at UM in Missoula, where he teaches undergraduate classes such as Galaxies and Cosmology, Introductory Physics and Modern Physics.
Maureen, in turn, took the lead on starting an orchard near Stevensville when not working half-time as an engineering consultant. The couple now has 420 cherry, plum, pear, apricot and apple trees that produce fresh fruit for local restaurants and schools. They also have a bright 6-year-old son, Joshua Orion Reisenfeld.
“My wife gives the marching orders with the orchard, but, yeah, I’m a fruit farmer on the side,” he says the day he was interviewed for this story. “I got up at 5 a.m. this morning and started plowing.”
Reisenfeld, now 44, was followed to UM by research assistant professor Paul Janzen, 40, a Canadian with an eerily similar career path, as he also studied at Harvard as a graduate student before working in Los Alamos. Janzen, however, is more of a dedicated laboratory researcher and doesn’t teach classes. Together he and Reisenfeld have used their connections to involve UM in multiple NASA space probe missions that have resulted in startling discoveries.
“They call us Los Alamos-north now,” Reisenfeld chuckles. “But we’ve published enough papers and have a good enough track record to forge our own reputation here at UM.”
In fact, Reisenfeld, Janzen and Los Alamos colleague Herb Funsten recently landed a three-year $800,000 grant to design a new mass spectrometer for future NASA space missions. Funding was provided by NASA’s Planetary Instrument Definition & Development Program. They call the device they are designing SITOF-MS for Spatially Isochronous Time-of-Flight Mass Spectrometer.
Mass spectrometers are devices that measure the atomic masses or molecular mass present in a given sample. A mass spec on the Cassini spacecraft detected the water erupting from Enceladus and the nitrogen coming off Rhea.
Reisenfeld said mass spectrometers such as the one they will design take in a gas and ionize the sample. Electric fields then are used on the ionized particles to determine their mass. As an example, hydrogen has an atomic mass of one, and helium is four. However, most previous mass specs have trouble differentiating certain atomic signatures. Common diatomic nitrogen and carbon monoxide, for instance, both have an atomic mass of 28.
Mass specs exist that can tell the difference between N2 and CO, but they are large and consume a lot of power, which isn’t an option for many space missions. Reisenfeld says one on the Rosetta space probe, now en route to a comet, can tell the difference, but that device is costly and about 4 feet long.
“The mass spectrometer we are designing will be much smaller — about the size of a 12-pack,” he says. “It will need much fewer resources in terms of power requirements and mass. Basically we are using new technologies to solve the same problem, but in a more cost-effective way.”
Reisenfeld says the trick to their new mass spectrometer technique is that it will do the job in two stages. First it will measure the mass of the molecules, and then it will break up the molecules into their constituents and measure the masses of the pieces. CO is made up of carbon (mass 12) and oxygen (mass 16). So if the device first detects a mass-28 molecule and then detects one carbon and one oxygen atom, you have carbon monoxide. If you just detect nitrogen atoms (mass 14), you have N2.
He says NASA doesn’t have a specific mission in mind for their device yet. Instead the space agency wants them to work in the laboratory to create a prototype that will be spacecraft-ready soon.
“It’s hard to go from an idea to something you want on a spacecraft in one step,” Reisenfeld says. “You don’t want to risk the idea not working. So the idea is to risk $800,000 in advance development instead of putting a $100 million mission at risk.”
He says their mass spectrometer will “sniff” samples in low-density gas environments, such as the Earth’s moon, Mars or Europa (a moon of Jupiter that likely hides a water ocean beneath its icy surface). The device should work well on orbiting spacecraft, but it could be used on a lander as well.
Reisenfeld says SITOF-MS will be engineered at Los Alamos, but the scientific functionality of the instrument will be tested in UM’s Space Science Lab, located in the basement of the Clapp Building.
During testing the mass spec will be placed within an airless calibration chamber. An ion source will shoot an ion beam into the chamber at the mass spec. Reisenfeld, Janzen and student assistants will know the mass, energy and charge state of the particles entering the chamber.
“So our device had better be seeing the same thing we are putting in,” he says. “Otherwise we’ll know we have some tweaks and work to be done.”
Reisenfeld has worked on many NASA missions during his career. Besides Cassini’s mission to Saturn, he helped with Ulysses, a spacecraft that studied the solar wind coming from the sun, and Deep Space 1, a probe that did a flyby of a comet in 2001.
He helped build the solar wind concentrator on Genesis, a probe that gathered charged solar wind particles during a three-year journey in space to determine the composition of the sun with unprecedented precision. Genesis was designed to return the samples safely back to Earth, but sadly it crashed in the Utah desert when a parachute failed to open in September 2004. The hard landing made a mess of the Genesis sample collectors, but the probe’s science team was able to salvage information from the wreckage and last summer published its results in an article that made the cover of Science.
The Genesis samples suggest the sun and its inner planets may have formed differently than scientists previously thought. The data revealed slight differences in the types of oxygen and nitrogen present on the sun and planets. Although the differences are minimal, the implications could help determine how our solar system evolved. Reisenfeld has a grant to continue analysis of the Genesis data.
While Reisenfeld and Janzen have had minor roles on some missions, they are key players for NASA’s Interstellar Boundary Explorer spacecraft, or IBEX, which was launched in 2008 to map the edge of the solar system. In 2009 the IBEX science team announced it had detected a vast ribbon of energized particles surrounding the entire solar system.
Reisenfeld says the IBEX mission gave him one of the chief “Eureka!” moments of his career. While studying data in his UM office, he was able to determine that there is a one-to-one correlation between the solar wind pressure coming off the sun and the energetic neutral atoms bouncing back toward IBEX from the edge of the solar system.
“So if the solar wind pressure doubles, the ENA pressure doubles,” he says. “It’s a perfect correlation. I got cold chills when I was looking at the graphs and saw this, and I was like ‘Paul (Janzen), can you come up here for a minute? Is this telling me what I think it’s telling me?’
“It’s cool because it means we understand something better.”
Reisenfeld has just submitted a paper to The Astrophysical Journal about how the distributed ENA signal coming back from the heliosheath, a region surrounding the entire solar system, changes over time.
Applying for NASA funding is not for cowards or people who lack perseverance. IBEX has made some amazing discoveries, but Reisenfeld says the probe was submitted for NASA funding three times before it was selected. This is not unusual. His research team also had to submit the mass spectrometer design project three times before NASA agreed to fund it. Reisenfeld says he and his colleagues spend a lot of time submitting proposals and updating ideas that are rejected.
The latest project he wants funded is the Coronal Physics Investigator. This new mission would investigate the mechanisms that heat the sun’s corona and release the magnetic energy that accelerate solar wind particles. The corona, which extends 10 million kilometers into space from the sun’s surface, is a mystery to scientists because it reaches temperatures of more than 1 million degrees Kelvin, and the surface of the sun — while still scorching — is only 5,000 K. Scientists don’t fully understand how this is possible.
“We know the sun’s magnetic field has something to do with it,” Reisenfeld says, “but how that massive magnetic field releases the energy is a big mystery.”
The coronal investigator resembles a small telescope and would be mounted on the International Space Station. The instrument looks at the flaring corona surrounding the sun while discarding light from the sun’s disk, creating what’s called a coronagraph. The light from the corona goes into an optical spectrometer, which can reveal what’s in the corona, the charge state, the density and the velocity.
When Reisenfeld was a Harvard graduate student, his and Janzen’s adviser was John Kohl, the principal investigator for an instrument called a coronagraph on the Solar and Heliospheric Observatory spacecraft. SOHO was a big mission in the ’90s to study the sun. Reisenfeld says the coronal investigator would have an upgraded version of Kohl’s SOHO coronagraph.
“This is the first time I’ve pitched a mission as the lead author,” he says, patting the 100-page proposal sitting on his desk. “This was painful. It took me a week of all-nighters to get this written.”
Reisenfeld says Kohl is still the PI for the coronal investigator, and the UM researcher’s official title on the project is program scientist. He says Kohl has tried to upgrade the SOHO coronagraph three times, and this will be the fourth attempt.
NASA intends to select two primary explorer missions with their own rockets and one or two “missions of opportunity,” in which an instrument is added to somebody else’s spaceship. The coronal observatory would be a mission of opportunity.
Forty-two proposals were submitted to NASA during this most recent solicitation, and Reisenfeld’s team learned in September that the Coronal Physics Investigator had made the cut to the next round.
“The next step is to carry out a concept study that would be due next September,” he said. “The final selection will be in March 2013.”
If funded, the UM portion of the project would receive $4 million over six years. It also would bring a 45-foot-long instrument used to calibrate sun-studying space probes to UM, where the one-of-a-kind device would be reassembled in the basement of the Interdisciplinary Science Building. Right now the instrument is in pieces at a Harvard warehouse.
“If this happens, we would be the only place in the world that could build instruments like this,” Reisenfeld says.
He loves that the interconnected modern world allows him to design probes and do advanced space science while living in the mountains of Montana. He also enjoys the opportunity to teach UM students and share his NASA experiences with them. In addition, he gets to employ some of Montana’s brightest undergraduate students in his laboratory to work on projects such as the Coronal Physics Investigator.
“I’m very excited about that proposal, but if we don’t get it, we’ll propose something else,” Reisenfeld says. “It’s not this or nothing. One way or another, we’ll get that unique world-class instrument here to UM.”
For more information email firstname.lastname@example.org.
Research Assistant Professor Paul Janzen works on an ion source in UM’s Space Science Laboratory, located in the basement of the Clapp Building.
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