NASA and JAXA bounce laser beam between Moon surface and lunar orbit

 

SLIM on the lunar surface captured by the LEV-2 rover (SORA-Q). Credit: JAXA / TOMY / Sony Group Corporation / Doshisha University.

NASA’s Lunar Reconnaissance Orbiter (LRO) twice transmitted a laser pulse to a cookie-sized retroreflector aboard JAXA’s SLIM lander on the Moon and received a return signal.

On May 24, 2024, as LRO passed 70 kilometers above SLIM (Smart Lander for Investigating Moon) during two successive orbits, it sent a signal to the lander with its laser altimeter instrument as it had done eight times before. But on both attempts, the signal bounced back to LRO’s detector.

This is a significant advancement for NASA, as the craft is not in an optimal position. Retroreflectors are typically attached to the top of landers, giving LRO a 120-degree range of angles to aim at as it sends laser pulses at the approximate location of a retroreflector. However, the SLIM lander touched down on the surface with its top oriented sideways, limiting LRO’s range.

To increase its chances of hitting its target, the LRO team worked with JAXA to determine SLIM’s exact location and orientation. NASA engineers then predicted when LRO’s orbital path would bring it to the coordinates that would give it the best chance of hitting SLIM’s retroreflector with the laser beams.

“The LRO altimeter was not designed for this type of application, so the chances of locating a tiny retroreflector on the lunar surface are already low,” said Xiaoli Sun, who led the team that built SLIM’s retroreflector at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, as part of a partnership between NASA and JAXA.

“The fact that the LRO team was able to develop a retroreflector that points sideways, instead of skyward, shows that these little devices are incredibly resilient,” Sun said.

NASA and JAXA bounce laser beam between Moon surface and lunar orbit

NASA’s laser retroreflector array installed on JAXA’s SLIM lander prior to launch. Credit: JAXA

SLIM landed on the moon’s surface on January 20. The retroreflector on board the lander, called the Laser Retroreflector Array, is one of six that NASA has sent to the moon aboard private and public landers, and the second to beam back to the LRO altimeter.

The first time a laser beam was transmitted from the LRO to a NASA retroreflector and vice versa was on December 12, 2023, when the LRO beamed a signal to ISRO’s (Indian Space Research Organisation) Vikram lander. Since then, the LRO has exchanged laser signals with Vikram three times.

NASA’s retroreflector consists of eight cube-shaped quartz prisms housed in a 2-inch-wide, domed aluminum frame. Requiring no power or maintenance, the retroreflectors can remain on the Moon’s surface for decades, providing reliable beacons for future missions.

Retroreflectors could guide Artemis astronauts to the surface in the dark, for example, or mark the location of spacecraft already on the surface to help astronauts and uncrewed spacecraft land nearby.

LRO’s laser altimeter, the only laser instrument orbiting the Moon so far, was designed to map the Moon’s topography to prepare for missions to the surface, not to pinpoint to within 1/100th of a degree of a retroreflector, which is what LRO engineers try to do with every ping.

Quote:NASA, JAXA bounce laser beam between moon surface and lunar orbit (2024, July 29) retrieved July 30, 2024 from https://phys.org/news/2024-07-nasa-jaxa-laser-moon-surface.html

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