The University of Arizona has begun building EMILIA-3D, one of three science investigation payloads selected by NASA earlier this year to be delivered to the moon by a future Commercial Lunar Payload Services, or CLPS, lander.

Short for EMission Imager for Lunar Infrared Analysis in 3D, the three-sensor package was selected under the Payloads and Research Investigations on the Surface of the Moon: Stand-Alone Landing Site-Agnostic, or PRISM SALSA, program.

It will allow scientists to study the interplay between lighting conditions, small-scale topography and temperature to create three-dimensional thermal models of the dusty lunar soil, called regolith. Ultimately, this can help the U.S. better image and navigate the moon's surface.

EMILIA-3D includes the Stereo Visible Imaging System, SVIS, and the Thermal Infrared Imager, TIR.

SVIS will provide stereovision with two eye-like cameras, while TIR captures temperature data. Both are mounted on a gimbal, which will be built by Rocket Lab Robotics (Motiv). The gimbal will allow the sensors to scan the lunar surface from the bottom of the lander to the horizon every eight hours for two weeks, the equivalent of one sunrise to sunset on the slowly revolving moon. As the sun slowly pushes and pulls shadows across the land, the sensors will do their work.

Filling an important gap

"The stereo images will be combined with thermal measurements at the centimeter- to meter-scale to create a totally new dataset of the lunar surface. This will help fill an important gap in data, since most images of the lunar surface are taken by the Lunar Reconnaissance Orbiter, which are comparatively low-resolution at this scale," said Sarah Sutton, EMILIA-3D principal investigator and photogrammetry program lead in the U of A Lunar and Planetary Laboratory. "Data returned by EMILIA-3D will feed into a sophisticated thermal model that shows how heat may transfer through the surface horizontally as well as vertically. Ours will be the first measurements of the lunar surface at this scale to support and improve 3D thermal models."

The team is specifically interested in temperature data in terms of small-scale surface structure, which can be quite craggy. Even the smallest of shadows can create a frigid environment that harbors volatiles, which are chemical compounds that vaporize at low temperatures, such as water ice on the moon. Also, because regolith doesn't conduct heat well, it warms up quickly in daylight but remains cold just beneath the surface, where volatiles may lurk.

"Understanding how human exploration affects volatiles, such as water, will be important before Artemis astronauts land at the lunar south pole," said Andy Ryan, a co-investigator and EMILIA-3D's science team lead. Ryan led the project proposal, which was supported in part by the Arizona Space Institute, when he was a U of A staff research scientist. Now, he's head of mining and payloads at AstroForge, a deep-space mining company. "Homing in on the correct physics will have important implications for where water ice could be stable and if human activity could destabilize it."

Beyond studying volatiles, heat flow through regolith can also reveal something about its physical properties, such as particle size and compaction in the near subsurface, giving insight into the geologic history of the surface.

Examining the effects of exploration

Another science objective is to observe how the thruster blast from the lander scours the surface and changes the thermal measurements from within that zone. This will shed light on the effects of exploration on the near-surface and inform the design of equipment, instruments and gear, according to the team.

The proposal required the payload be designed to achieve its science objectives from anywhere on the moon and from any lander.

The team now has 24 months to prepare the instrument for delivery to NASA. To reduce risk, the sensors will be derived from elements that have already demonstrated success on other missions, according to Sutton. For example, SVIS and TIR – EMILIA-3D's eyes – are based on Northern Arizona University's VISIONS instrument, short for VISible and Infrared ObservatioN System, which is currently on its way to Mars on NASA's ESCAPADE mission.

"VISIONS proved that NAU can design and build what we call science-grade cameras – instruments that combine off-the-shelf and custom parts engineered to survive the harsh conditions of space," said Chris Haberle of NAU, EMILIA-3D's deputy principal investigator and camera instrument scientist. "With EMILIA-3D, we're taking that same approach from a Mars mission to the surface of the Moon."

There's also support from the Technology and Research Initiative Fund – or TRIF, a state fund to drive innovation and economic development at universities – to build a thermally controlled vacuum chamber. This chamber is distinct because it will be filled with mirrors to view to the simulated lunar surface at different angles much like EMILIA-3D will. These lab measurements will aid in interpretation of actual lunar surface data. This effort is led by U of A LPL researcher Michael Phillips. 

"EMILIA-3D is an exciting opportunity to perform infrared stereo imaging to study the moon's surface in a new way," said LPL associate professor Dani DellaGiustina, who is serving as a project scientist. Along with experience on other missions, she served as deputy principal investigator for OSIRIS-REx and now leads OSIRIS-APEX. "My role is to help the team connect the science goals to the practical realities of building and operating a NASA instrument, drawing on lessons learned from our Artemis LEMS seismometers, OSIRIS-REx, OSIRIS-APEX and other planetary missions. Sarah has a really strong team, and I'm excited to support her leadership and help ensure EMILIA-3D is positioned for success."

Other team members include U of A's Carina Bennett and Cameron Dickinson, Kenneth Edmundson of Edmundson Photogrammetry, NAU's Christopher Edwards and Kristen Bennett, University of Hawai'i, Manoa's Matthew Siegler, University of Central Florida's Phil Metzger, U.S. Geological Survey's Randolph Kirk, Colorado University, Boulder's Paul Hayne, and Mines Paris-PSL' Daniel Pino Muñoz and Marc Bernacki.