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Tiny moonbound spacecraft have very big goals

Artist's concept of water ice trapped in sunshine-shy craters on the moon.
Artist's concept of water ice trapped in sunshine-shy craters on the moon.
(Image: © Hongyu Cui/Lunar Trailblazer)

When you reflect on big-time science at the moon, think small. 

NASA's new megarocket, the Space Launch System (SLS), is scheduled to launch from Florida in late 2021 on its debut mission. That flight, known as Artemis-1, will send NASA's Orion spacecraft on an uncrewed trip around the moon — and loft more than a dozen tiny cubesats to test inventive technologies as well.

Among those bantam spacecraft are Lunar IceCube, Lunar Flashlight and LunaH-Map. And we can soon add to the moon mix Lunar Trailblazer, a smallsat mission headed for flight in 2024 as a hitchhiker payload on NASA's Interstellar Mapping and Acceleration Probe (IMAP) mission.

Related: What is NASA's Artemis program?

The three NASA-sponsored cubesats and the smallsat are being readied for moonbound treks to help quench a thirst for new data about lunar water ice. Such data could help sustain an Artemis Base Camp for wide-ranging lunar exploration, NASA officials have said.

All that said, hunting for moon water remains no slam dunk.

Measurement strategies

A long-time advocate of cubesat investigation of the moon is Pamela Clark, director of the Cubesat Development Lab at NASA's Jet Propulsion Laboratory (JPL) in Southern California. She is the science principal investigator on Lunar IceCube, which is being built at Morehead State University in Kentucky.

"All of these cubesat missions have the search for volatiles, especially water in various forms, as a primary goal," Clark said.

Lunar IceCube, for instance, will be placed in a nearly polar equatorial periapsis orbit (the point at which the orbiting craft is closest to the moon), with a "repeating" coverage pattern allowing it to observe swaths of the lunar surface at different times of day over several 28-Earth-day lunar cycles, Clark told Space.com. 

Lunar IceCube will carry an instrument called the Broadband InfraRed Compact High Resolution Explorer Spectrometer (BIRCHES), which will prospect for water in ice, liquid and vapor forms.

While the coming smallsat and cubesat missions have differing observational and measurement strategies as they orbit the moon, Clark said that each spacecraft will provide a unique perspective on lunar water distribution. That collected data, when combined, "will greatly increase our understanding of the origin and history and current locations of volatiles as potential resources on the moon and analogous surfaces throughout the solar system," she said.

Related: The search for water on the moon in photos

Shaded polar regions

Lunar Flashlight has been developed by a team from JPL, NASA's Marshall Space Flight Center in Alabama and the University of California at Los Angeles. This mooncraft will use near-infrared lasers to shine light into shaded polar regions near the south pole to detect volatiles on the moon. Meanwhile, an onboard reflectometer carried by the briefcase-sized orbiter will gauge surface reflection and composition. 

UCLA will be providing the ground data system, which will plan the instrument observations and process the data.

"The observations made by the low-cost mission will provide unambiguous information about the presence of water ice deposits inside craters that would be a valuable in-situ resource for future Artemis missions to the lunar surface," explains JPL's website about the mission.

Then there's Arizona State University's Lunar Polar Hydrogen Mapper, or LunaH-Map for short. The "H" in the probe's name is silent "because the hydrogen is hiding in the permanently shadowed regions," explains the ASU mission website.

The shoebox-sized LunaH-Map will chart hydrogen enrichments within permanently shadowed regions of the lunar south pole. The probe has a miniaturized propulsion system, attitude control, power and communications systems to maneuver into orbit around the moon. It will navigate into a low-altitude polar orbit, attaining its lowest point smack-dab over the lunar south pole.

Temperature profiles

The California Institute of Technology's Lunar Trailblazer is the "smallsat" of the bunch, a larger spacecraft intended to investigate lunar water and lunar geology. Lunar Trailblazer is outfitted with an instrument called the High-resolution Volatiles and Minerals Moon Mapper (HVM3) from JPL, and another, the Lunar Thermal Mapper, from the University of Oxford in England.

In July 2020, Lockheed Martin Space was selected as the new partner for Lunar Trailblazer's flight system. The company will design and build the spacecraft, integrate the instruments, and work with rideshare services to ready Lunar Trailblazer as a secondary payload aboard IMAP's launch atop a SpaceX Falcon 9 rocket.

"Our goal is to determine the form, abundance, and distribution of water on the moon, including water ice in the permanently shadowed regions," said Lunar Trailblazer principal investigator Bethany Ehlmann, a scientist at Caltech and JPL. Lunar Trailblazer is designed to provide the best maps of the distribution of water ice at the surface in the permanently shadowed regions via direct detection with the HVM3 imaging spectrometer, she said.

HVM3 data, paired with simultaneously measured temperature profiles, will allow researchers to zero in on the abundance of water and how temperature controls it, Ehlmann told Space.com.

Remaining unknowns

While researchers are confident the moon's polar regions are enhanced in volatiles, there remain some unknowns about the form and physical distribution of these volatile species.

For example, are there skating rinks of ice on those permanently shadowed crater floors? Or are those floors studded with ice-coated rock grains, or ice grains separate from rock grains? 

Those are questions posed by Kirby Runyon, senior staff scientist for planetary geology and exploration at Johns Hopkins University's Applied Physics Laboratory in Maryland.

"We really don't know how the ice is distributed or how it's concentrated in the moon's polar regions," Runyon said. "Smallsats orbiting very low — just thousands of feet above the south pole's craters — can use neutron detectors and maybe radar to map out the ice. Once we know where it is and how it's concentrated, then surface vehicles can be designed to go mine it."

Related: Moon mining could actually work, with the right approach

Sustained habitation

Experts agree that there's early need for more and finer data about the chemistry of lunar water ice, including possible contaminants, and the physical form of ice-regolith mixes. Without that information in hand, planning mining projects, setting up processing plants and establishing production checklists will remain pipe dreams.

The most important resource at the lunar poles are the areas of sustained illumination that can be found in both the north and south, said Samuel Lawrence, a planetary scientist at NASA's Johnson Space Center in Houston. He is also an emeritus chair of the Lunar Exploration Analysis Group (LEAG), an advisory group to NASA.

Lawrence said that there are only a handful of these areas, which will enable NASA and its commercial and international partners to bootstrap existing or planned technologies available in the near term, particularly for power generation. That work, in turn, will enable sustained habitation for gradually increasing amounts of time. 

"So, in a very real and immediate sense, it is actually the sustained illumination regions which are the most important near-term resources … and the reason why the Artemis program is targeting polar landing sites for the Artemis Base Camp," Lawrence said. But the global resource potential of the moon — meaning both polar and nonpolar resources — is vast, he added.

"Fifty years from now, people will be making a profit from lunar resources. We want American companies to be part of that story, and the steps we will take in the next decade are the first chapter in an exciting story," Lawrence concluded.

Leonard David is author of the recently released book, "Moon Rush: The New Space Race" published by National Geographic in May 2019. A longtime writer for Space.com, David has been reporting on the space industry for more than five decades. Follow us @Spacedotcom, Facebook or Google+. This version of the story published on Space.com.

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