NASA's Lunar Flashlight will use lasers to search for water ice at the Moon's poles

The SmallSat will use a four-laser reflectometer, with near-infrared wavelengths that are easily absorbed by water, to identify ice on the Moon's surface.
Deena Theresa
This illustration shows NASA’s Lunar Flashlight over the Moon. The SmallSat mission will have a very elongated orbit, taking it within 9 miles (15 kilometers) above the lunar South Pole to search for water ice in the Moon’s darkest craters.
This illustration shows NASA’s Lunar Flashlight over the Moon. The SmallSat mission will have a very elongated orbit, taking it within 9 miles (15 kilometers) above the lunar South Pole to search for water ice in the Moon’s darkest craters.

NASA 

In a few weeks, a small satellite will shine a light on the permanently shadowed craters of the Moon, looking for reservoirs of water ice that could be highly beneficial to astronauts.

NASA's Lunar Flashlight, the size of a small briefcase, is scheduled to launch aboard a SpaceX Falcon 9 rocket from Cape Canaveral Space Force Station in Florida between November 9 and 15 with the Japanese Hakuto-R lander and United Arab Emirate’s Rashid 1 rover.

Though the presence of water below the lunar regolith is known, scientists are uncertain whether surface ice frost covers the floors inside these cold craters. And because they are at the poles, at regions where the Sun never rises above crater rims, there is no way to find out, unless there is some source of light.

And that's exactly what the SmallSat intends to do - use lasers to shed light on these dark craters in the lunar South Pole.

"This launch will put the satellite on a trajectory that will take about three months to reach its science orbit," John Baker, the mission’s project manager at NASA’s Jet Propulsion Laboratory in Southern California, said in a statement. "Then Lunar Flashlight will try to find water ice on the surface of the Moon in places that nobody else has been able to look."

NASA's Lunar Flashlight will use lasers to search for water ice at the Moon's poles
The solar-powered small satellite is shown here with its for solar arrays extended in a Georgia Tech clean room.

The second NASA mission to follow a near-rectilinear halo orbit

As the Lunar Flashlight carries only a limited amount of propellent, fuel-intensive orbits aren't possible. Mission navigators will guide the spacecraft way past the Moon, which will then settle into a "wide, looping, science-gathering orbit".

A near-rectilinear halo orbit requires far less fuel than traditional orbits, and "will take it 42,000 miles (70,000 kilometers) from the Moon at its most distant point and, at its closest approach, the satellite will graze the surface of the Moon, coming within nine miles (15 kilometers) above the lunar South Pole", according to the release.

"The reason for this orbit is to be able to come in close enough that Lunar Flashlight can shine its lasers and get a good return from the surface, but to also have a stable orbit that consumes little fuel," said Barbara Cohen, Lunar Flashlight principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

A reflectometer will detect the presence of water

Lunar Flashlight will be touching a few milestones: It will be the first interplanetary spacecraft to use a new kind of "green" propellant than the commonly used in-space propellants such as hydrazine. The former will be safer to transport and store and was developed by the Air Force Research Laboratory. It burns via a catalyst, rather than requiring a separate oxidizer, hence is called a monopropellant.

The spacecraft will also be the first mission to use a four-laser reflectometer to look for water ice on the Moon. The reflectometer will use near-infrared wavelengths that are easily absorbed by water to identify ice on the surface. Interestingly, when the lasers hit a bare rock, their light will be reflected in the spacecraft, thereby gesturing a lack of ice. If the light is absorbed, it means that the dark craters do contain ice.

"We are going to make definitive surface water ice measurements in permanently shadowed regions for the first time," said Cohen. "We will be able to correlate Lunar Flashlight’s observations with other lunar missions to understand how extensive that water is and whether it could be used as a resource by future explorers."

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