As it journeys into some of the darkest and coldest spots in the solar system, NASA’s new water-hunting Moon rover, Volatiles Investigating Polar Exploration Rover (VIPER), will need some very robust headlights to light the way.
In the extremes of light and dark found on the Moon, shadowed and lit areas are in such high contrast that any contours in the landscape are effectively invisible in the darkness. To navigate this world, VIPER’s rover drivers will rely on a system of rover-mounted lights and cameras to steer clear of boulders, descend steep declines into craters and avoid other potentially mission-fatal dangers. To make sure the first-ever lighting system on a rover will reveal obstacles hiding in the shadows, the VIPER team recently tested prototypes in a high-fidelity recreation of a lunar landscape at NASA’s Ames Research Center in California’s Silicon Valley, where the mission is led.
Tests like these are helping the VIPER mission – which in August passed the important preliminary design review milestone with NASA’s Planetary Science Division and the independent VIPER review team – solve for the many unique challenges of operating on the Moon.
“We face similar challenges as any car designer,” said Uland Wong, VIPER’s navigation hardware lead and a computer scientist at Ames. “Whether it’s on a rover or the next model of sedan, a bad lighting design means a driver can’t see details in the landscape. We have to pay extra attention to these challenges on the Moon because once VIPER gets there, there’s no coming back.”
Other lights do exist in space, such as single LEDs inside microscopes on Mars rovers and lights that help spacecraft dock to the International Space Station. But the harsh environment of the Moon combined with VIPER’s specific goals to find water in deep, dark places make this the first rover to require car-like floodlights. While Mars science objectives typically allow those rovers to operate in sunlit areas, VIPER’s solar-powered mission will venture into spots that never receive direct sunlight, due to the Moon’s tilt and the very low angle of the Sun at the South Pole.
VIPER’s lights will be arrays of LEDs and will offer the same flexibility as your car’s high beams and parking lights. Mounted on a mast, two of these arrays will cast a narrow, long-distance beam. Around the base of the rover, as many as six lights will illuminate a broad area less intensely and can be turned on and off individually, as needed.
During the recent testing at Ames, the team tried out several robust LED candidates to see which offered the best optical performance and how best to position them to handle backscattering, or reflection of light back in the direction from which it came. This is a dramatic problem on the Moon, because the surface is covered in powdery dust that reflects a lot of light, blinding VIPER’s cameras.
“We are developing the lights in an iterative manner,” said Wong. “We start with some candidates and get to understand their performance though testing, then whittle them down for the best optical performance.”
Several candidate light designs were set up on tripods around the lunar test bed. A realistic lunar landscape had been sculpted out of the simulated lunar soil. The team lit this terrain as it would appear in different areas at the Moon’s poles, with either very low-angle illumination simulating the Sun, or in total darkness. They turned on the candidate lights, took photos like VIPER will do one day, and are now comparing the quality of the images obtained.
The Ames-based team will pass their findings on to VIPER teammates at NASA’s Johnson Space Center in Houston where the lights will eventually be built. Together, they’ll choose the top two candidates, and the one that can most easily and quickly pass the rigorous testing to qualify for spaceflight will earn the heavyweight title of first headlight on a NASA rover.
VIPER is a collaboration within and beyond the agency. VIPER is part of the Lunar Discovery and Exploration Program and is managed by the Planetary Science Division of NASA’s Science Mission Directorate at NASA Headquarters in Washington. NASA's Ames Research Center in California's Silicon Valley is managing the project, leading the mission’s science, systems engineering, real-time rover surface operations and flight software. The hardware for the rover is being designed and built by NASA's Johnson Space Center in Houston, while the instruments are provided by Ames, NASA's Kennedy Space Center in Florida, and commercial partner Honeybee Robotics in Altadena, California. The spacecraft, lander and launch vehicle that will deliver VIPER to the surface of the Moon will be provided by Astrobotic, who was selected through NASA’s Commercial Lunar Payload Services, or CLPS initiative, delivering science and technology payloads to and near the Moon.