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Shuttle flight delivers JPL air-quality monitoring instrument to space station
Shuttle flight delivers JPL air-quality monitoring instrument to space station

Thanks to the delivery of a new instrument developed by JPL and successfully launched Monday, April 5, astronauts aboard the International Space Station may soon be breathing a bit easier.

Photo: Members of the Vehicle Cabin Atmosphere Monitor team, from left: Ara Chutjian, Dan Karmon, Jim Hofman, Benny Toomarian, Murray Darrach, John MacAskill, Stojan Madzunkov, Arvid Croonquist and Richard Kidd.

Aboard the STS-131 mission to the station is the Vehicle Cabin Atmosphere Monitor (VCAM), an instrument designed by a JPL team led by Ara Chutjian, supervisor of the Atomic and Molecular Physics Group.

The instrument, a gas chromatograph/mass spectrometer, will operate for one year aboard the space station. Its primary goals will be to analyze organic chemicals in the air, measure concentrations of the major atmospheric components (nitrogen, oxygen, carbon dioxide) and monitor any events such as chemical spills and cleanups within the cabin.

“The space station is the testbed for these sorts of long-duration space flights,” said Murray Darrach, also from the Atomic and Molecular Physics Group, the co-investigator on the project. “Astronauts and everything on ISS give off gasses: their food, clothes, metabolism, all materials. They need to know what they’re breathing and they need to be able to monitor those gasses.”

Darrach said it took three-and-a-half years for several teams to bring the idea full circle. The proposal for VCAM came about after NASA sent out a broad call for instrument ideas, in which the idea submitted by JPL was awarded.

“VCAM is the first-ever gas chromatograph/mass spectrometer to be built and delivered by JPL,” Chutjian said, adding that the Lab was responsible for providing the instrument’s electronics and writing all software; system fabrication, assembly and testing were also carried out on Lab.

The atmosphere monitor is roughly the size of a microwave oven and weighs about 25 kilograms. Enclosed within its metal exterior are three main components that process the air: first, a small preconcentrator, followed by a gas-chromatograph column and a mass spectrometer. The steps in which the air is processed are important in order to get sensitive and accurate readings of trace species at parts-per-million to parts-per-billion concentration levels.

The technique by which chemicals are identified, the “fragmentation” or “fractionation” pattern, refers to how the gasses are broken down by ionization. The instrument identifies ions from the fragmentation pattern in conjunction with the length of time the chemicals spend in the gas chromatograph column. Each species spends a characteristic amount of time (known as the elution time) within the column.

Readouts from the instrument show the presence of “mass fingerprints” of chemicals as spikes on a graph in which the area of a peak corresponds to the concentration of each particular gas, said Darrach. If the instrument does detect a hazardous level of any particular chemical, the astronauts can be alerted, proper precautions taken and a subsequent cleanup process initiated, to remediate the atmosphere.

Once VCAM is powered up, it is no longer necessary for astronauts to operate the instrument. It is entirely self-contained and self-supporting, with internal gas canisters that allow it to work for up to a year. The instrument will be controlled by ground operations at JPL when needed, but will otherwise function autonomously, checking the air once a day and reporting back to computer servers on Lab.

Chutjian’s team finished validating the flight unit in October 2009, after which it was taken to Kennedy Space Center and packaged into a multi-purpose logistics module.

But even in storage, awaiting delivery to STS-131 and launch, Chutjian said the instrument is still absorbing a lot of molecules, which “may obscure the operation of the mass spectrometer.” Therefore, during the first several weeks onboard the station the instrument will be cleaned through pre-programmed operating steps: “It’s ready to start working after all the molecular species are encouraged to desorb,” he added. A replica of the VCAM flight model is being used on Lab to conduct further validation and testing.

Further plans for instruments such as VCAM include prototypes for a water module that will be able to extract organic species from the potable water on missions, as well as to keep tabs on the concentrations of both benign and toxic species in the water.

“The idea is to put together a testbed of a number of different monitors: air, water, surfaces, bacteria,” Darrach said. “These instruments are all about heritage. Once you deliver and fly, it becomes easier because you have the gravitas already to get there.”

Beyond VCAM’s basic use as a “toxicology report for astronaut health,” as Darrach puts it, Chutjian also noted the use of these instruments in almost any environment: for unmanned planetary missions, to measure isotopic ratios, for explosives detection and national security, and as terrestrial field instruments.

Story by Catherine Sum and reprinted with permission from JPL Space, JPL's internal news source.

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