Lunar Trailblazer, the NASA mission led by the California Institute of Technology (Caltech) in the US to understand the properties of water on the Moon and its cycle, is one step closer to launch next year. Two instruments will try to determine the abundance, places, shape and how water on the moon changes over time, after previous observations confirmed that there is water on the moon.

In early December, the Jet Propulsion Laboratory delivered a key science instrument to Lockheed Martin Space in Colorado, and teams integrated it with the SmallSat small satellite.

The information gathered by the two instruments will provide data on the lunar water cycle and help inform future human missions about where water reserves can be found and mined as a resource.

Two instruments will gather information about the Moon’s water resources

The instrument, called the High-resolution Volatiles and Minerals Moon Mapper (HVM3), is one of two on the Lunar Trailblazer probe. HVM3 will detect and map water on the Moon’s surface to determine its abundance, where it is, its shape and how it changes over time, according to

“The calibration and integration of HVM3 is an important milestone as, after three years of hard work, the team has delivered the key scientific instrument. It’s a very exciting time,” said Walton Williamson, systems engineer at JPL and manager of the HVM3 instrument.

The other instrument, the Lunar Thermal Mapper, a multispectral infrared imager, is being developed by Oxford University in the UK and is scheduled to be delivered and integrated in early 2023.

HVM3 mission

Selected under NASA’s Small Innovative Missions for Planetary Exploration (SIMPLEx) program in 2019, the probe Lunar Trailblazer it measures just 3.5 meters wide with its solar panels fully deployed, but it’s a compact spacecraft with far-reaching goals.

While previous observations have confirmed that there is water on the Moon, the distribution and form of the water is uncertain. HVM3, an imaging spectrometer, will provide clues by mapping the spectral signatures, or wavelengths of reflected sunlight, of different forms of water in the lunar landscape to make high-resolution maps.

Where exactly could water molecules be found on the surface of the Moon?

For example, water molecules could be trapped inside lunar rocks and regolith (the dusty layer that covers the Moon) and could be deposited for short periods of time as frost in cold, shadowy areas. As the Sun moves across the sky during the lunar day, the shadows also move, cycling these water molecules into the lunar exosphere and transporting them to other cold places where they can re-deposit as frost.

The most likely places where water ice exists in significant quantities are the permanently shadowed craters at the lunar poles, which are key targets for science and exploration.

A refined sensibility

To differentiate between these different forms of water, how they move and where they are, the HVM3 has two key features that set it apart from other spectrometers. The first is its ability to detect a wide range of infrared wavelengths that are readily absorbed by various forms of water. The second is its sensitivity to these wavelengths: HVM3 is designed to be sensitive to low light levels, which will be essential for discovering the water that can be found in the moon’s darkest craters.

“Measuring the permanently shadowed regions of the lunar surface will be the most difficult part of the mission. To observe the possible ice on the floor of these craters that have not seen sunlight, we will use the light scattered by the walls of the nearby sunlit craters,” said David R. Thompson, JPL principal scientist and HVM3 instrument investigator.

Lunar Thermal Mapper Mission

While HVM3 will search for water, the Lunar Thermal Mapper will detail the temperature properties of the lunar surface. Together, these will give scientists a more detailed understanding of how surface temperature affects the distribution of water on the Moon.

“This mission was designed specifically to unravel the mystery of water on the Moon by mapping its distribution while helping us understand whether it is locked in the lunar material or covers the surface as ice in cold spots. I am extremely proud of the Trailblazer team for completing this important tool delivery milestone. We are now focusing on the next phases as we get closer to launch,” said Bethany Ehlmann, Lunar Trailblazer principal investigator at Caltech.

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