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NASA Laser Hit an Oreo-Sized Mirror on the Moon from Orbit
Pew pew!
Nature never intended for us to leave the planet. As a result, sending people and spacecraft into space comes with a unique set of challenges. Just ask the crew of The Ark, streaming now on Peacock. They’ve got to travel 4.2 light-years across deep space just to get to the nearest star. Making that happen means aiming your ship with incredible precision from one moving target to the next. They aren’t traveling to where Proxima centauri b is, but to where it will be when they arrive.
Something similar plays out in real world space exploration, albeit on a smaller scale. Getting a spacecraft to its destination and being able to communicate with it on the other side, often means hitting incredibly small targets across vast distances. Success requires a level of aim that bends the brain, and NASA’s Lunar Reconnaissance Orbiter (LRO) might just be the most impressive sharpshooter in the solar system.
NASA Dunked a “Cookie” in Laser Light from Orbit
Recently, the LRO fired a laser from orbit and hit a reflector the size of an Oreo cookie 62 miles away on the surface of the Moon. The reflector is mounted to the ISRO’s (Indian Space Research Organization) Vikram Moon lander, which touched down at Shiv Shakti point in the Moon’s southern region on August 23, 2023.
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On the afternoon of December 12, 2023, NASA sent a command to the LRO, telling it to fire its altimeter instrument at Vikram. The LRO usually uses that instrument to map the surface of the Moon. It works by firing five lasers all at once and measuring the time it takes for the light to hit the surface and bounce back. Because the speed of light is constant in a vacuum, it’s a reliable way of getting high-detail scans of the Moon’s terrain, outlining craters and boulders that astronauts can reference to navigate on future missions. This time, NASA wasn’t aiming for the surface, but for a two-inch reflector aboard Vikram.
When the laser light bounced back and was received by the LRO, NASA knew their experiment had worked. “We’ve showed that we can locate our retroreflector on the surface from the Moon’s orbit. The next step is to improve the technique so that it can become routine for missions that want to use these retroreflectors in the future,” said Xiaoli Sun, who led the team that developed the retroreflector on Vikram as part of a partnership between NASA and ISRO, in a statement.
The instrument, dubbed the Laser Retroreflector Array, is made up of eight quartz-corner-cube prisms arranged inside an aluminum dome. That configuration allows the retroreflector to collect and bounce back light from any direction. That means an orbiting spacecraft can hit it on the move as long as its aim is good. Similar devices are in use aboard the International Space Station (ISS), providing a way for spacecraft to line up during docking maneuvers, according to NASA.
By placing them on lunar spacecraft, future astronauts could use them to find markers on the Moon’s surface even if visibility is poor. Rather than looking out the window for a telltale crater to figure out their position, astronauts could just ping a reflector to figure out precisely where they are. In order for that to happen, we need to place a bunch of reflectors in useful places, and we need to get better at hitting them.
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NASA and ISRO’s recent success only happened on the eighth attempt. For this to be really useful, the orbiter needs to hit its target reliably, every time. Even though the LRO shoots five different beams, each one 10 meters wide by the time it hits the surface, it has to aim to within one-hundredth of a degree to hit its target; no easy feat. Future tests are planned to identify challenges and improve performance.
In the meantime, we’re sending more retroreflectors to the Moon. There is one aboard JAXA’s SLIM lander, which recently achieved an impressive precision landing within 100 meters of its target but isn’t operating correctly. It’s unclear if the retroreflector will be usable. Another reflector is mounted to Intuitive Machine’s Nova-C lander, scheduled for launch in February. If successful, it will give astronauts a useful landmark at the Moon’s South Pole when Artemis III returns humans to the Moon for the first time since 1972.
In the meantime, catch up on the complete first season of The Ark, streaming now on Peacock.
