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NASA scientists are expanding the sensitivity of an electronic nose, while shrinking its size to make it more compact for future
space missions following a Space Shuttle flight that successfully demonstrated the technology.

“The E-Nose was able to determine changes in humidity accurately, which we confirmed using an independent humidity monitor in
the shuttle cabin,” said Dr. Amy Ryan, principal investigator for E-Nose at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “While
we would have liked to monitor any of the ten common contaminants the E-Nose was trained to smell, fortunately for the crew none
was detected. That was confirmed with air samples brought back in canisters from the flight.”

The ability to monitor recycled air is very important to the space program, especially in closed environments such as the Space
Shuttle, the International Space Station and any future space outpost that features a closed human habitat. Early detection of potentially
harmful spills or leaks is essential so that crew members can immediately take action to remedy the situation. Even if a human nose
could detect every possible odor and identify it, fatigue or a cold would impair the nose’s sensing ability.

“Space crews are very, very busy,” said Ryan. “Anything we can do to automate their tasks and keep the space habitat safe is
highly desirable. Now we need to further develop E-Nose’s capability to detect various odors and differentiate between those that
signify danger and those that do not. We are working with people at other NASA centers to optimize this technology.”

Since there are limits on size and power requirements in constricted quarters, miniaturization is important. The unit flown on
STS-95 is only about the size of a large paperback, weighs 1.4 kilograms (about 3 pounds), including the operating computer, and uses
an average of 1.5 watts of power. Dimensions are 18.5 by 11.5 by 12 centimeters (7-3/4 by 4-1/2 by 4-3/4 inches).

“Our current efforts are directed towards improving the sensitivity of the E-Nose, expanding the compounds we can detect from
12 to 24, and making the unit even smaller,” Ryan said. “Decreasing the size and weight will be pretty straightforward, since the shuttle’s
space allocation requirements dictated the special box we used for that flight.”

A major application that JPL scientists are pursuing is the detection of a fire before the blaze erupts. Fires can smolder in closed
areas, such as insulation in paneling or around wires, for some time before flames actually appear. With early detection, the fire can be
extinguished safely before much damage occurs. The many potential commercial uses include “sniffing” for unexploded land mines; for
spills in chemical plants that could contaminate workers; for plant ripeness to harvest at the desired point in the agricultural cycle; and
for possible diagnosis of disease based on odors from human perspiration and breath.

The JPL E-Nose flown on the Space Shuttle used sensor technology from the California Institute of Technology in Pasadena. The
project is managed for NASA’s Office of Life and Microgravity Sciences and Applications.
JPL is managed for NASA by Caltech.

An image of the electronic nose, with caption, is available at