Trailblazer of the Week

Robert O. Green

14 August 2020

For over 30 years, Robert O. Green has worked at NASA and JPL pursuing science with imaging spectroscopy. He has no intent of stopping anytime soon.

“Each year it gets more exciting and the opportunities are growing,” says Green, a Lunar Trailblazer co-investigator closely tied to the build and calibration of its imaging spectrometer, the High-resolution Volatiles and Moon Mineralogy Mapper (HVM3). “Every day I am involved with the deployment and development of advanced imaging spectrometers to enable new science for NASA.”

Given his tenure over the past three decades, it’s not surprising Green has contributed his imaging expertise to many different space missions, including the Mars Reconnaissance Orbiter CRISM imaging spectrometer. He also worked as the instrument scientist for the Moon Mineralogy Mapper (M3), the spectrometer that first discovered lunar water.

“I find great fulfillment when a new, high fidelity imaging spectroscopy measurement is used to make a discovery or address an open scientific question,” Green says.

The form, abundance, and distribution of lunar water are the key unknowns now driving Green and the Lunar Trailblazer team. The mission’s orbiter will use state-of-the-art imaging spectroscopy, in conjunction with a thermal imager, to further advance our understanding of the properties of water on the Moon’s surface. According to Green, understanding how lunar water exists and behaves will ultimately inform our thinking about water on other solar system objects.

“Water is an important molecule on Earth and throughout the solar system,” explains Green. “New knowledge about lunar water and its form advances our scientific knowledge about the Moon and processes in the solar system.”

Green also alludes to water’s functional imperative to humans, as both a biological necessity and for industrial utility.

“Lunar water has the potential to be an important resource for the next generation of solar system exploration,” he says.

For Trailblazer, Green is working closely with the engineering team to design and eventually calibrate the HVM3 spectrometer within a select range of light to detect water’s unique spectral signature. At the infrared wavelength of 3 micrometers, the distinct absorptions associated with water and hydroxyl become notably visible. However, since scientists initially assumed water was not present on the illuminated surface of the Moon, Green’s original instrumentation for M3 was not optimized to fully assess this 3-micrometer region. HVM3 is now tasked with thoroughly advancing measurements at and beyond the 3-micrometer range. Once reflected off the Moon’s surface, light will be detected by a state-of-the-art detector array within HVM3’s optical system, which can then be translated into an electronic signal. By detecting spectra of lunar light, HVM3 will determine water’s characterization and spatial distribution.

Equipping HVM3 to inherit and expand M3’s wavelength detection has in turn prompted Green and the science team to ask questions beyond the scope of any past lunar mission. Green finds Lunar Trailblazer’s science objectives very compelling and shares some of the other serendipitous discoveries HVM3 could make.

“There are organics elsewhere in the solar system,” Green says. “Could there be organics on the Moon?”

In addition to Trailblazer’s HVM3, Green is also the instrument scientist for the Mapping Imaging Spectrometer for Europa (MISE) on NASA’s forthcoming Europa Clipper mission. MISE will address questions related to the Jovian moon’s habitability. He is also the principal investigator of the Earth Surface Mineral Dust Source Investigation (EMIT), which will use an imaging spectrometer from the International Space Station to measure mineral composition in the Earth’s arid land dust source regions to advance understanding of the heating and cooling impact of mineral aerosols at the regional and global scale for our planet.

When he isn’t measuring reflected sunlight, Green can be found spending time with his family outdoors.

“I love to camp and backpack in the Sierra Nevada,” he says.

Whether it’s the personal pursuit of a mountain’s summit or Trailblazer’s determination to map water ice at the Moon’s south pole, Green surely appreciates the importance of packing only what you need.

“Lunar Trailblazer is a wonderfully compact and focused mission,” he says. “The science and development teams are exceptional. I am incredibly fortunate and want to share this opportunity with others.”



Robert O. Green is the HVM3 instrument scientist and Trailblazer of the Week!

Trailblazer of the Week is an ongoing series showcasing the diversity of experience and expertise that supports the collective determination of the Lunar Trailblazer mission.

By Emily Felder
Emily Felder is a Pasadena City College student and Caltech intern working on science communication for the Lunar Trailblazer mission.