Rosetta

CREDIT: ESA/Rosetta/Philae/CIVA

Breakthrough of the Year: Hitchhiking to 67P/Churyumov-Gerasimenko

The European Space Agency’s (ESA’s) Rosetta mission has made history several times this year. Launched on 2 March 2004, the spacecraft traveled more than 6 billion kilometers across the solar system to finally reach its target—the comet 67P/Churyumov-Gerasimenko—on 6 August. It was the first time a spacecraft built by humans has rendezvoused and orbited a comet. Then, on 12 November, Rosetta dropped a small, automated scientific laboratory onto the surface of 67P. It bounced and went into hibernation prematurely, but the Philae lander was still able to operate for 57 hours, transmitting back to Earth unprecedented data.

Comets are fascinating objects—primitive balls of ice, dust, and gas believed to hold clues to the origin of the solar system. Because comets contain water and organic molecules, they may also have played a role in seeding life on Earth. “Rosetta is trying to answer the very big questions about the history of our Solar System. What were the conditions like at its infancy and how did it evolve? What role did comets play in this evolution? How do comets work?” stated ESA Rosetta project scientist Matt Taylor in a press release issued on the day Philae landed.

We did have a fully automated sequence which had taken about 2 years to prepare for what would happen on touchdown, with each instrument in turn doing its own analyses. That was thrown out of the window.

—Dan Andrews

Opportunities to work on space missions are few—and, hence, very special. And being part of such a large, high-profile, long-term scientific endeavor carries challenges. Science Careers asked three young scientists involved in the Rosetta mission to tell us about their work and their careers.

Following her lucky star

Cecilia Tubiana

Cecilia Tubiana

Courtesy of Cecilia Tubiana

Cecilia Tubiana became a space scientist more out of a passion for math and physics than for the sky and what it contains. She obtained a Bachelor of Science degree in physics and a master’s degree in environmental and solar physics from the University of Torino in her native Italy. For her master’s research, she investigated how the abundance of certain radioactive elements in meteorites is connected with variations in solar activity. “It made me understand that what I wanted to do was not theoretical physics. … I don’t work in a lab, but what I like is to work with data, get the data, and understand them.”

Tubiana went to do a Ph.D. with Philae lead scientist Hermann Böhnhardt in Katlenburg-Lindau, Germany (now in Göttingen, Germany), not so much for the research itself as for the high-level international environment at the Max Planck Institute for Solar System Research (MPS). What really attracted her was the opportunity to make ground-based space observations in Chile. Her project was to observe and characterize 67P. “This is how my career in this field started. ... It was more following what was offered [at] that moment.”

During her Ph.D., which she carried out between 2005 and 2008, Tubiana spent nine nights making photometric and spectroscopic observations at the European Southern Observatory’s Very Large Telescope. In those years, the comet was near its maximum distance from the sun, and inactive. “The comet appeared as a dot,” Tubiana says. “But still … if it’s a good quality, bright [dot], then you can do a lot of things.” Tubiana characterized the comet’s shape, size, color, albedo, rotational period, and surface composition.

Rosetta was far from Tubiana’s mind when she was studying the comet from the ground, she says. She just enjoyed her Ph.D. and realized only later how useful her research was: Those planning the mission needed to have a better picture of what state the comet would be in when Rosetta arrived there.

After graduating, with 6 years to go before the space encounter, she decided to take a front seat. She took a postdoc with Holger Sierks, in the same department, to work on OSIRIS—the Optical, Spectroscopic, and Infrared Remote Imaging System mounted on Rosetta to capture high-resolution images of the comet. She worked on improving the calibration of OSIRIS images to get the camera ready for comet observations, using skills she had gained in Chile. Then, with more than 40 experts in modeling, sequence programming and commanding, spacecraft maneuvering, acquisition of observations, and data analysis, she helped develop OSIRIS’s science plan, deciding what to observe and how to make it happen.

This week's Science includes a <a href="http://scim.ag/1C5Q61y">special section</a> on the Breakthrough of the Year: The Rosetta mission. Rosetta captured headlines when its lander touched down for the first time on the surface of a comet.

This week's Science includes a special section on the Breakthrough of the Year: The Rosetta mission. Rosetta captured headlines when its lander touched down for the first time on the surface of a comet.

For Tubiana, a very exciting moment in the mission came last January when Rosetta woke up from more than 2 years of induced hibernation. “Things could have gone wrong,” she says. “When that signal came, that was really saying, ‘OK, now we start.’ ” Images started pouring in a couple of months later. Initially “the comet … was like the [dot] that I was used to in my ground-based images,” she says. But as the spacecraft was approaching the comet, the dot revealed “first the shape and then all details of the surface.” What OSIRIS was seeing from space was in line with the general portrait that Tubiana had drawn of the comet during her Ph.D., which she finds gratifying. The new information helped the mission choose a landing site for Philae.

Working on OSIRIS is “very interesting, … very motivating,” Tubiana says. But also “it’s a very high-pressured job. It’s very tiring, because we have a lot of things to do with very strict deadlines.” The closer Rosetta got to the comet, the more and faster Tubiana and her team had to work. It was all the more challenging for her because she was on maternity leave for 4 months until September 2014, and while she kept track of events, she had to catch up on how to do things just as curtain time approached. A supportive team, a space-scientist husband, and parents who help her at home have all been very important in allowing her the time to succeed, she says. “When you see these amazing images as they are coming now … this gives you payback for all the efforts that you are doing.”

Philae has landed and sits inert. But “the mission doesn’t stop there,” Tubiana says. OSIRIS still has to capture the action on the icy comet as it approaches the sun and then starts retreating; the mission will last at least another year. “Now we have a lot of time still to come, a lot of data to come, and a lot to still discover and study,” Tubiana says. “This is the right place … to be now.”

Swinging with Mars

Dan Andrews

Dan Andrews

Courtesy of Dan Andrews

Dan Andrews was 5 when he made his first space observation. His grandfather had bought him a toy telescope, “and I could see the moon, Saturn’s rings, that sort of stuff,” he says. Since then, his interest has never really waivered. Working on a mission like Rosetta is something “I always wanted to [do], but I never thought I’d really have the chance.”

Andrews earned a degree in aeromechanical systems engineering from the Royal Military College of Science (now part of the Defence Academy of the United Kingdom’s College of Management and Technology) in 2002. He took a temporary job at the Open University’s Milton Keynes campus, where the Beagle 2 lander was being designed to search for traces of life during ESA’s 2003 Mars Express mission. “I thought if I could get a job on campus, I could somehow secure a position on the mission,” he says.

Soon, Andrews was working as a technician in the Aseptic Assembly Facility’s clean room for Beagle 2, soaking in the science and engineering behind the mission’s equipment. By the time the Mars Express orbiter was launched, in June 2003, Andrews had joined the mission’s science team as a postgraduate researcher. Using spare instrumentation under space conditions, he tested the Gas Analysis Package—the principal instrument onboard Beagle 2, whose role was to make stable isotope measurements of gases including hydrogen, oxygen, nitrogen, and carbon dioxide. He also helped in the Lander Operations Control Centre at the National Space Centre, preparing procedures for the operation of Beagle 2 on Mars after its planned landing in December 2003.

Then, after separation, Beagle 2 vanished, never to be heard from again. “I was absolutely distraught. We put our hearts and souls into it,” Andrews says.

The Mars experience propelled Andrews onto the Rosetta mission, starting at the March 2004 launch. Joining a core team of six led by Ian Wright of the Open University, Andrews pursued a Ph.D. working on the Ptolemy instrument. Ptolemy was designed to analyze the distribution of elements such as hydrogen, carbon, nitrogen, and oxygen in the comet’s nucleus and perhaps to link them, through their isotopic composition, to the origin of oceans, simple organic molecules, or the building blocks of life on Earth.

At first, Andrews worked mostly on the engineering side, figuring out whether the instrument had survived the launch intact by comparing it with a spare instrument in the lab. Over the years that followed, he gained experience running the instrument and knowledge of how it performed in space. He earned his Ph.D. in 2008, took a postdoc, and then became a project officer in Wright’s lab.

In 2010, as Rosetta flew past the asteroid Lutetia, the Ptolemy team collaborated with other instrument teams in an attempt to detect an exosphere; they may have succeeded, but they’re not sure. “The flyby of Lutetia was a very complex process,” he says. “That was great experience getting ready for the comet.” As time progressed, the team focused on getting Ptolemy ready for Philae’s landing while sampling the comet’s atmosphere during Rosetta’s approach.

Andrews witnessed the touchdown from the Philae Lander Control Centre in Cologne, Germany, while also watching the action at the European Space Operations Centre in Darmstadt, Germany, which controlled Rosetta, on video screens. The two centers simultaneously received the first touchdown signal, and “the room in Darmstadt absolutely erupted … with celebrations,” Andrews recalls. But in the lander control center, “we knew something hadn’t gone quite right” from spacecraft data, Andrews says. “We could see that the loose spacecraft had bounced … and we were back in space spinning.” There were some nervous moments.

Philae settled back onto the comet, but it was not as healthy or well located as planned. “We did have a fully automated sequence which had taken about 2 years to prepare for what would happen on touchdown, with each instrument in turn doing its own analyses. That was thrown out of the window,” Andrews says. The instrument teams and ground segment controllers had to decide what to do on the spot. “That was fantastic to be involved in, just to see the teamwork. Because we’ve known each other for 10 years, we all knew pretty much what everyone was thinking.”

The most important lesson Andrews learned from the experience, he says, is to keep the big picture in mind and not jump to conclusions. “It’s very easy to … miss little nuances and miss vital clues of what’s going on,” he says. In spite of the pressure, you have “to sit back, to look at all the information available, process it, and talk to other people.”

Ptolemy was able to sniff the comet’s atmosphere near the surface repeatedly. An experiment they ran just before Philae’s batteries ran out allowed them to attempt to capture the composition of the material that accumulated in one of Philae’s ovens during the landing and make some isotopic measurements. Plans to use a drilling system to analyze the composition of the comet’s subsurface were scrapped in order to give an opportunity to Ptolemy’s sister instrument, the Cometary Sampling and Composition (COSAC) system. “Even though it was not a nominal landing, we still have fantastic results, and every instrument operated.”

Andrews is now working to analyze the Ptolemy data, which have already shown the presence of water and many simple organic compounds. He is waiting to see if Philae springs back into life as the comet approaches the sun. “There’s every chance that we will get enough energy into the batteries to reboot. And then the fun begins again.”

Gravitating toward Rosetta

Chaitanya Giri in front of the COSAC vacuum test chamber at the Max Planck Institute for Solar System Research

Chaitanya Giri in front of the COSAC vacuum test chamber at the Max Planck Institute for Solar System Research

CREDIT: Fred Goesmann

Chaitanya Giri, like Andrews, developed a fascination for the sky while still a child. “[I] had this dream in my heart that I wanted to work on a space mission,” Giri says. But he knew that opportunities would be scarce, especially in India, where he grew up.

Giri was only 17 when he started drawing a mental map of what missions were going on and who was working on them. “I started very early reading research papers, so I was very much familiar with what’s happening where,” he says.

Giri earned a Bachelor of Science degree in chemistry followed by a Master of Science degree in biophysics from the University of Mumbai. For his master’s research, he used remote sensing to determine variations in greenhouse gas concentrations around the Lonar crater, an impact crater in central India now filled with a lake containing methane-producing microorganisms. He also conducted field research to map the crater’s hydrology. The Lonar crater is held as a rare terrestrial analog for the study of geochemical processes on Mars, and a poster Giri presented during an international symposium in Ahmedabad in 2010 led to a joint paper with Earth and planetary scientists at the University of Tokyo and Chiba Institute of Technology.

Giri was able to secure a Ph.D. position in the lab of Fred Goesmann at MPS, in the same department as Tubiana, to work on the COSAC experiment aboard Philae. After starting in August 2011, Giri worked to optimize COSAC for successful operation after the landing, using a lab replica. The mission of COSAC is to analyze the composition of the comet’s nucleus with (in contrast to Ptolemy) a focus on heavier molecules such as complex organics, possibly including amino acids.

Life on Earth relies exclusively on left-handed amino acids; COSAC also aims to determine whether this chiral bias exists on the comet as well. That would be a clue as to whether prebiotic molecules on Earth could have been seeded by extraterrestrial bodies. To prepare for the possibility that COSAC might find such a chiral bias, Giri also worked under the supervision of Uwe Meierhenrich of the University of Nice-Sophia Antipolis in France to simulate interstellar conditions at the SOLEIL synchrotron in Paris, seeking an explanatory light-radiation phenomenon.

Giri’s Ph.D. project was short and intense because everything had to be ready for Philae’s landing in November. The most difficult time came when the Max Planck Institute relocated from Katlenburg-Lindau to Göttingen. Starting in September 2013, there was a “6-month period when I never had that instrument in my hand. That was difficult because there were a lot of things pending at that time,” Giri says.

Giri defended his thesis a couple of months before the landing. He is now working as a postdoc, helping to analyze the data. The COSAC team got several sniffs of the gases present at the surface, but they're still not quite sure what happened with the drilled sample; so far they have found no sign of it. That’s disappointing, because this was probably the most highly anticipated experiment. Like Andrews, Giri is hoping for another shot as 67P approaches the sun, increasing the odds of recharging Philae’s batteries.

“I came very late on this mission … but it was a great moment to see the faces of people who have given their lives to this mission” as data were pouring in, Giri says. “It gave me a feeling that, yeah, I should do something like this in my career … a mission as great as Rosetta, or even greater than Rosetta.”

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