Trailblazer of the Week

Kerri Donaldson Hanna

22 May 2020

Traveling, hiking, baking—and measuring moonlight.

These are just a few of Dr. Kerri Donaldson Hanna’s favorite activities. As a Lunar Trailblazer co-investigator working with the Lunar Thermal Mapper (LTM), Donaldson Hanna is tasked with making precise measurements of lunar light to better understand the geology and composition of the Moon’s surface. On its own, the human eye can only view objects as they reflect light within the visible spectrum of electromagnetic radiation. However, objects can also emit their own light, beyond our visible spectrum, and this infrared light is a product of surface temperature as well as composition. A thermal imager like LTM measures emitted infrared light at select wavelengths, and Donaldson Hanna is fine-tuning these channels to reveal the Moon’s composition.

“I am excited to participate, for the first time, in a mission from its conception all the way through to the first observation made,” says Donaldson Hanna. “I get to take the research I began as a graduate student, expand on it, and learn even more about the Moon.”

As a graduate student at Brown University, Donaldson Hanna was lucky enough to participate on two separate missions, both with the primary objective of investigating the lunar surface. Her first mission was working on the Diviner Lunar Radiometer Experiment aboard NASA’s Lunar Reconnaissance Orbiter (LRO). Donaldson Hanna’s contributions on Diviner helped produce compositional maps of the Moon’s rocks and soils based on its emitted radiation. The second mission she took part in was on the Moon Mineralogy Mapper (M3), which discovered water on the Moon, generated a mineralogical map of the Moon, and was included on India’s very first lunar spacecraft, Chandrayaan-1.

“Lunar Trailblazer is building on what we learned from both of those instruments and pushing each a bit further by expanding their capabilities,” Donaldson Hanna says.

Diviner’s observations, for the first time, mapped temperatures within the Moon’s polar regions, pin-pointing locations exceedingly cold enough for water ice to form. M3 in turn captured unprecedented infrared spectra, indicating an increased presence of hydroxyl (OH), molecular water (bound H2O), and water ice toward higher, polar latitudes. Trailblazer forges a new path in our understanding of the lunar surface by mapping temperature, water (composition and abundance), and mineralogy at higher spatial resolutions using two paired instruments: LTM and the High-Resolution Volatiles and Moon Mineralogy Mapper (HVM3). The channels Donaldson Hanna is optimizing for LTM mean that Trailblazer will be able to determine rock compositions associated with water-enriched areas better than ever before.

Working at the forefront of lunar exploration on Diviner and M3 was a seminal experience for Donaldson Hanna.

“Growing up on a small farm in Missouri, I dreamed of working for NASA and being an astronaut someday, but it was hard to envision how that might happen,” recalls Donaldson Hanna, who now runs her own lab as an Assistant Professor in the Physics Department at the University of Central Florida (UCF). “Certainly when I began graduate school at Brown, I felt a bit closer to that goal, because I was getting to work on my very first space missions, but I never quite realized how my experiences and the colleagues that I met would put me where I am today.”

As a new faculty member in the Planetary Sciences Group at UCF, Donaldson Hanna balances teaching, advising, and research responsibilities on a daily basis. Setting up new equipment, taking spectral measurements, and conducting remote sensing analysis is what she most looks forward to between office hours.

“The most challenging part, and I think this is true for almost everyone, is carving out a good amount of time to get into the lab and do the fun stuff,” Donaldson Hanna says.

As an airless body, the Moon was initially presumed to be completely void of water and lacking any indication of complex igneous rock formations, such as silicic volcanism. Diviner compositional observations suggested differently; certain surface regions exhibited spectral features consistent with silicic lithologies. Lunar rocks now appeared to be more evolved than previously thought, beckoning further inquiry. As a postdoctoral research fellow at the University of Oxford, Donaldson Hanna used Diviner’s thermal infrared observations of the Moon to simulate these unique near-surface conditions in the laboratory. From there, she began designing spectral channels that can be used to refine the characterization of lunar rock compositions.

“I was lucky as a postdoc to work with colleagues at Oxford on the development of radiometers for solar system airless bodies, particularly the selection of bands for mapping their composition,” explains Donaldson Hanna. “In my last year at Oxford, we were asked by Principal Investigator Bethany Ehlmann to join the Trailblazer team and build the thermal instrument, and the rest is history! I think the part of my role, so far, that has been important and fulfilling is helping in the selection of the filter widths and wavelengths for LTM. This is a huge decision because we are essentially deciding what data will be key and what we will be providing to the lunar science community.”

Design and assembly of LTM is now underway at Oxford, but where, exactly, would such an instrument measure the intensity of infrared light emitted from the Moon? Luckily, Donaldson Hanna isn’t just involved with LTM’s metrics, but establishing its principal mapping locations as well.

“I have been involved with picking interesting craters and regions on the Moon to target during Trailblazer's mission,” she says, and further expounds on the benefits of thermal mapping for In-Situ Resource Utilization (ISRU), or the physical collecting and processing of surface material for use on the Moon by future explorers. “Lunar water could be used in the future in a range of ISRU capabilities for our long-term exploration of the Moon and the rest of our Solar System.”

Lunar Trailblazer’s prioritization to map locations targeted by Donaldson Hanna and the Trailblazer team could, for example, quantify the abundance of water in polar regions, providing a better understanding of how much water is available for ISRU.

“Trailblazer will map out where water is and will point future landers and rovers to the ideal locations for doing those studies,” she says. “Forward to the Moon we go!”

Dr. Kerri Donaldson Hanna is the Trailblazer of the Week! You can follow her on Twitter.
Trailblazer of the Week is an ongoing series 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 working on science communication for the Lunar Trailblazer mission.