FEATURE
Measuring Dust Motes
Instrument Prototype Could Help Scientists Understand Dust Problem on the
Moon and Mars
While chasing down the swirling towers of dust that frequently crop up in the deserts of the American Southwest, research physicist Brent Bos experienced an “ah-ha” moment.
Although he could measure the dust particles that fell in and around the mini-cyclone he was tracking that summer day 5 years ago with a customized microscope attached to a camera, he couldn’t measure the individual particles’ characteristics and dynamics while they were entrained within the vortex. “That’s when I started thinking about other optical techniques that would allow me to see the particles inside,” he recently recalled.
For Bos and a team of other Goddard scientists, seeing the particles that make up these whirling plumes of dust and grit isn’t just an academic question.
Dust devils also occur on Mars, apparently driven by the same physical mechanisms that form their cousins on Earth. Dust also presents a severe challenge on the Moon, where ultra-tiny particles levitate in all directions and at various speeds, adhering to everything with which they come into contact.
Dust Characterization Applications
Having an instrument that could measure dust particle sizes, concentrations, and velocities obviously would have practical applications for NASA’s Exploration Systems Mission Directorate, Bos reasoned — especially since the sensors that obtain these measurements on Earth won’t work in the low-pressure atmospheres found on the Moon and Mars. Current sensors don’t monitor trajectories, either.
“What we need to know is what’s going on at a particle level. We needed to see these particles in flight,” Bos said.
And so began his effort to build an instrument — the Large Depth-of-Field Particle Image Velocimeter (PIV) — that would gather these measurements and give scientists needed insights into the lunar and Martian dust environments and how engineers might mitigate the dust problems before astronauts explore these worlds in the coming years.
The prototype instrument, funded in part with Goddard Internal Research and Development (IRAD) funding, features an “afocal” optical design that looks promising, Bos said. During a field campaign in Arizona 1 year ago, Bos was able to detect dust particles as small as 5-10 microns in size.
|
Dust devils, like the one captured in this photo, are driven by the same physical mechanisms that form their cousins on Mars. Goddard Principal Investigator Brent Bos is now developing an instrument that would measure the count, shape, size, velocity, and trajectory of dust particles to better understand their characteristics on the Moon and Mars.
|
Not Ready for Prime Time — Yet
But Bos said his instrument concept is not ready for prime time — yet.
To obtain images needed to determine particle count, shape, size, velocity, and trajectory, the instrument generates about 4 gigabytes of data every 3-1/2 minutes of operation. Space-based operations, even those in the future, unlikely will be able to transmit such large datasets.
Consequently, Bos and Co-Investigator Scott Antonille are using IRAD funding to develop algorithms that can autonomously identify, measure, and track the dust-particle signals measured by the PIV. The aim is to significantly reduce the amount of data that a flight-ready PIV would downlink back to Earth.
Other Applications
Characterizing the lunar and Martian dust environments isn’t the only application, Bos said. On the Moon, for example, dust particles adhere to spacesuits and other equipment, posing potential health hazards to astronauts if the grit finds its way into living quarters. If installed inside an airlock, however, the PIV could measure the number and sizes of particles being expelled from astronauts and their gear, confirming that the grit had actually left the airlock.
“We want to continue maturing this technology, and ultimately win a flight opportunity on a lunar or Mars lander in the 2014 or 2015 timeframe,” Bos said. “With additional funding, I believe we’ll be able to meet that goal.”
|
