Trailblazer of the Week

David Thompson

12 May 2020

How many people does it take to get a spacecraft to the Moon? To find out, the Lunar Trailblazer mission is debuting Trailblazer of the Week, an ongoing series to spotlight a vital team member each week. With so many different roles contributing to an ongoing NASA mission, this feature offers a dynamic, inside perspective on an individual team member’s core objectives and personal reflections working on Lunar Trailblazer.

Dr. David R. Thompson, Lunar Trailblazer’s instrument scientist for the High-resolution Volatiles and Moon Mineralogy Mapper (HVM3), is our premiere Trailblazer of the Week!

“I’m thrilled to be the instrument scientist on HVM3,” says Thompson, whose work specializes in modeling spectral data to characterize planetary bodies. For Trailblazer, Thompson will model the data acquired by HVM3, an infrared imaging spectrometer, to help in the search for the distinct spectral signature and properties of water on the Moon’s surface.

“Imaging spectroscopy is a real data scientist’s playground,” says Thompson. “You can keep exploring a single scene for years, and still not find all its secrets.”

The “scenes” yet to be fully explored are lunar surface features. For Thompson, the objective of HVM3 will be to fully characterize the form and distribution of water on the Moon. Spectrometers like HVM3 will detect which wavelengths of light are absorbed and emitted by the Moon, and these measurements reveal “fingerprints” that correspond to its unique composition. In effect, spectroscopy can reveal known mineral, ice, and organic signatures.

“It wasn’t until I got to NASA’s Jet Propulsion Laboratory that I discovered imaging spectrometers and was immediately hooked,” says Thompson. “The whole concept of a spectrum for every pixel in the scene was mind-blowing. Being able to see the composition of anything seemed like a superpower.”

Thompson has always enjoyed playing with data. While attending graduate school and studying statistical machine learning, his focus was on robotic space exploration.

“Modeling science instrument data was particularly appealing,” says Thompson. “There is a bit of creative artistry in it; chiseling away at the messy, noisy, complicated world until you reveal the crystalline math underneath.”

To make Thompson’s task even more complex, the Moon- and all physical objects in general- both reflect sunlight and emit their own light, but at infrared wavelengths undetectable by the human eye. Distinguishing between sources of light and their unique spectral changes requires a sophisticated instrument like HVM3.

“Lunar Trailblazer will be making some really tricky measurements,” says Thompson, but he stresses that HVM3 is not acting alone; Lunar Trailblazer will utilize an additional instrument to generate a thermal map in tandem with HVM3.

“One special thing about Lunar Trailblazer is the way its two instruments work together. The Lunar Thermal Mapper instrument will be making really precise measurements of the surface temperature,” Thompson explains. “That helps us understand how much of the HVM3 signal comes from the surface thermal emission. Which, in turn, helps us make more accurate measurements of lunar water. It's like an assist play in basketball!”

Preparation for Lunar Trailblazer’s deployment has Thompson up bright and early. After a morning run, he’s typically logged on by 7 a.m. and ready to take on such complex, evolving data sets.

“No day is normal, since the puzzles are always changing,” he says. “Much of the day is dedicated to meetings, but free hours are devoted to writing and coding. Two or more free hours in a row is a chance to get in the coding ‘zone’ or to run some experiments.”

Thompson also notes that the coolest parts of the mission- both literally and figuratively- are the Moon’s Permanently Shadowed Regions (PSRs). As the name suggests, these are areas permanently shielded from the sun, resulting in “cold traps” where substantial amounts of water ice are presumed to be concealed by darkness. Thomspon recognizes that this poses a challenge to standard approaches of analyzing reflected sunlight.

“Instead, we will use the tiny bit of light that is reflected from nearby hills and crater walls. It will be a really challenging measurement, and everything will have to work perfectly for us to pull it off,” says Thompson. “I can’t wait to see what’s in there.”

Dr. David R. Thompson is the Trailblazer of the Week! Check out his website HERE.
Trailblazer of the Week is a weekly feature showcasing the diversity of experience and expertise that supports the collective determination of the Lunar Trailblazer mission.

By Emily Felder
Emily Felder is a Pasadena City College student and Caltech intern who is working on science communication for the Lunar Trailblazer mission.