How a tiny briefcase-sized spacecraft will prospect for water on the Moon

An artist’s illustration of the Lunar Flashlight mission. | Image: NASA

The Artemis I mission isn’t the only lunar mission happening this month. On Wednesday, November 30th, a SpaceX Falcon 9 is expected to launch a commercial Japanese lander called Hakuto-R to the Moon, carrying the United Arab Emirates Rashid rover. And there will also be an extra payload tucked inside the rocket: a tiny orbiter called Lunar Flashlight.

As part of a wave of increased commercial interest in the Moon, the lander could be among the first private missions to land on the Moon — although, as the Israeli lander Beresheet demonstrated when it crashed into the Moon in 2019, touching down safely on the Moon’s surface still remains a challenge that a private mission has yet to overcome. As for the small Rashid rover, this is the UAE’s first lunar mission, following its successful Mars orbiter mission, Hope, launched in 2020. NASA has also engaged commercial partners in its future lunar endeavors, from two planned SpaceX lunar landers to its Commercial Lunar Payload Services program, all in anticipation of future crewed lunar missions — with the first steps in getting humans back on the Moon including smaller missions like Lunar Flashlight.

The Lunar Flashlight mission consists of a small craft called a CubeSat, around the size of a briefcase, which will circle the Moon to search for ice on the Moon’s surface. Entering a highly elliptical orbit called a near rectilinear halo orbit, the satellite will make a close approach to the Moon’s south pole every six days, collecting data on each of 10 passes. It uses an infrared laser reflectometer instrument that operates at four different frequencies, bouncing lasers off the Moon’s surface to see whether the material being struck is ice or rock.

The satellite will come “within 20 kilometers of the surface of the Moon,” Glenn Lightsey of Georgia Tech, co-principal investigator for the Lunar Flashlight project, told The Verge. “Which, for a reference, that’s essentially the flight that an airliner flies over the surface of the Earth. So we’re essentially skimming the surface of the Moon when we’re making these science measurements.”

The increasing certainty among researchers that ice does exist on the Moon has led agencies like NASA to step up their interest in programs that could identify or access lunar ice. This includes missions like Lunar Flashlight and programs like the Break the Ice Lunar Challenge, which invites proposals for technologies that could mine ice.

There is also a scientific angle to the mission, as studying the distribution of ice across the Moon could help answer questions about the Moon’s history. It’s still an open question how this ice arrived on the Moon. It could have been deposited onto the surface by comets, or there could be natural processes that led ice to form there.

But the big emphasis is on enabling future crewed missions. “From a human exploration perspective, if there is significant quantities of ice at the Moon and we can access it, then that’s a game-changer for how we will explore the moon,” Lightsey said.

Water is important for human missions — not only for human consumption but also as it can be turned into oxygen and used as a fuel oxidizer. But water is heavy, so carrying it from Earth to the Moon isn’t practical for long-term missions. If there is accessible water already on the Moon, this can be used as a resource, in a principle called in-situ resource utilization.

Lunar Flashlight is just a first step in identifying usable ice deposits. It will create a map of ice in the south polar region with a resolution of around a kilometer or just over half a mile. This can be pinned down into more exact mapping by future projects like the VIPER lunar rover. Designed to locate ice deposits at the lunar south pole specifically, VIPER is scheduled for launch in 2024.

Data from Lunar Flashlight will also be supplemented by information gathered from other missions, such as the LunaH-Map and Lunar IceCube CubeSats, which recently launched with NASA’s new Space Launch System rocket as a secondary payload to the Artemis I mission. LunaH-Map is currently experiencing problems with its propulsion system, but if it is able to recover, it will use its neutron spectrometer to search for ice deposits beneath the lunar surface, while Lunar IceCube will look at how water is absorbed and released by the Moon’s regolith.

Taken together, these missions could help enable crewed Moon missions for periods of weeks or longer. “If there is ice there, it’s a big strategic factor in our long-range planning for how we will set up long-term habitation on the moon,” Lightsey said. “So we want to know how much there is and where it is. We’re essentially prospecting for lunar ice.”