Animation of NASA’s Volatile Investigating Polar Exploration Rover (VIPER) on the lunar surface. Photo credit: NASA Ames / Daniel Rutter
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As every seasoned traveler knows, a good map helps to get the most out of an adventure. Not unlike NASA’s first lunar robot, which will be sent to the moon in late 2023 to search for ice and other resources on and below the lunar surface. The Volatile Investigating Polar Exploration Rover, or VIPER for short, is part of the agency’s Artemis program. Without a lunar travel guide, VIPER’s mission planner created a new high-resolution digital elevation map of the lunar surface.
If equipped with this map, the rover will be in a better position to traverse the moon safely and efficiently while searching for resources at the lunar south pole. Ice is a resource of particular scientific interest because it has applications when it is discovered in outer space and converted into other resources to fuel exploration of our solar system such as oxygen and rocket fuel.
Measuring about one meter across, this map offers a 3D model of a large swath of terrain at the South Pole, showing the ever-changing light and temperature conditions caused by the long shadows sweeping across the landscape.
Illustration of NASA’s Volatile Investigating Polar Exploration Rover (VIPER) on the lunar surface. Photo credit: NASA Ames / Daniel Rutter
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This close-up view of the moon’s surface not only prevents the rover from tipping its steep crater, but also provides mission planners with important information to ensure the rover’s solar-powered battery remains charged and guides the rover to a safe hibernation location. when communicating Power outages during mission operations on Earth.
“We’re sending VIPER to one of the most dynamic environments on the moon, and the rover needs to be able to accept what the moon is giving us,” said Anthony Colaprete, VIPER project scientist at NASA’s Ames Research Center in Silicon Valley, California. “That’s why we created this unique map – on a human scale – to help us carefully plan routes for the rover while operating safely and gathering the best science possible.”
The map has revealed scientifically interesting new features on the lunar surface, including many “mini cold traps” – these are shady pockets on the lunar surface 2 to 5 meters in diameter – that may be cold enough to collect ice. These micro-cold traps provide areas to explore in addition to the much deeper and older craters that VIPER’s mission focuses on.
Spectacular slanted view from the edge of Shackleton Crater near the moon’s south pole. This crater has a diameter of about 21 kilometers. While nowhere on the moon remains continuously illuminated, the three points on its edges together remain illuminated by the sun for more than 90 percent of the year. These points are surrounded by topographic depressions that never receive sunlight, creating cold traps that can trap ice. The narrow-angle camera aboard NASA’s Lunar Reconnaissance Orbiter took this photo on August 1, 2006. Photo credit: NASA/GSFC/Arizona State University
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“We used to think water ice just collected in deep dark craters on the moon,” said Colaprete. “But we now believe that even small, dark craters can be cold enough to hold water molecules. These tiny cold traps are much more common than their larger counterparts, so understanding how they can store water is important for answering the more general question of how water behaves on the moon.
To create the altitude map, the Ames team used NASA’s open-source Stereo Pipeline software and the processing power of the Pleiades Ames supercomputer to overlay the thousands of satellite images captured by the camera aboard the Lunar Reconnaissance Orbiter.
Engineers combine these advanced tools and expertise with a photo processing feature called photoclinometry. This technique, also known as “Shaping of Shadows”, combines the well-known angle of incidence of sunlight with the gray level of many two-dimensional images to infer the three-dimensional shape of the lunar surface. The resulting lunar terrain model allows engineers to calculate how light and shadow play on the surface at any point in time in the past or future. With the help of models, they can, for example, predict the lighting at the time and place of the rover’s landing and plan the rover’s movements to stay in the sun and avoid shadows.
Illustration of NASA’s Volatile Investigating Polar Exploration Rover (VIPER) on the lunar surface. Photo credit: NASA Ames / Daniel Rutter
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With known lighting conditions, the team was able to create detailed temperature maps across a wide range of terrain, on the surface and slightly deeper than 2.5 meters. Temperatures can vary widely between 400 degrees below zero and 170 degrees Fahrenheit, making the lunar surface a chessboard a potentially promising and highly unlikely place to find ice. Armed with this new map, the team was able to pick places where there might be ice and send VIPER to take samples and check if the ice was showing up and, if so, how stable it would be under different lunar conditions.
“These high-resolution maps are really changing the way we think,” said Kimberly Ennico Smith, assistant project scientist for VIPER in Ames. “We’re starting to see how varied the soil conditions on the Moon are, even in areas we used to think were fairly uniform. This allows us to more precisely localize the rover drilling sites and collect even better scientific data.”
Members of the VIPER team, who are responsible for keeping the rover running, are excited to see what the rover expects in day-to-day life – or rather, minute by minute.
“The shadows move around the moon’s south pole at about the same speed as the rover,” said Mark Shirley, director of mission operations planning at Ames. “We have to plan ahead to prevent VIPER from being taken over by the dark – there isn’t much room for error.”
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