NASA and JAXA Achieve a Remarkable Feat: Bouncing Laser Beams on the Moon

In a significant achievement for space science and technology, NASA's Lunar Reconnaissance Orbiter (LRO) has successfully completed a complex laser communication test with a retroreflector positioned on the Moon's surface. The operation entailed the transmission of a laser pulse by the LRO to a small retroreflector on the Japan Aerospace Exploration Agency’s (JAXA) Smart Lander for Investigating Moon (SLIM), with the signal being successfully returned to LRO’s detector.

This technical triumph took place while LRO orbited 44 miles above SLIM on May 24, 2024. This is notable as the retroreflector, mounted on JAXA’s lander, faced sideways rather than upwards—posing an even greater challenge for the engineering team due to the limited angle range available to aim the laser pulse.

Typically, retroreflectors on lunar landers are designed to face the sky, allowing a broader targeting spectrum for laser instruments like the one aboard LRO. Despite their lander's less than optimal position, which was a result of SLIM's landing orientation, the collaboration between NASA and JAXA allowed for precise determinations of SLIM’s exact location and orientation, enabling the meticulous planning required for LRO’s trajectory to intersect with the retroreflector.

The feat was not without its complications. Xiaoli Sun from NASA's Goddard Space Flight Center, who led the development of SLIM’s retroreflector, recognized that LRO’s altimeter was not originally intended for such a delicate maneuver. The success of this exercise was a testament to the resilience of these small devices and the determination of NASA and JAXA's engineering teams.

The outcome of this collaboration is more than a scientific curiosity; it marks a critical step forward in space navigation technologies. Retroreflectors reflect laser light directly back to the source, requiring no power or maintenance, and are thus exceptionally reliable over long periods on the challenging lunar surface. This capability opens the door for enhanced guidance for Artemis astronauts landing on the Moon's surface, potentially even in the darkness of the lunar night, and aids the precise location marking of existing spacecraft to support future landings, both crewed and uncrewed.

LRO’s laser altimeter, the only one of its kind orbiting the Moon, was initially conceived to create detailed topographic maps to aid mission planning rather than engaging in pin-point laser targeting of a retroreflector. Despite this, the LRO engineering team is perfecting the use of the altimeter tool for such targeting, demonstrating adaptability and innovation in its mission since the orbiter's launch on June 18, 2009.

The phenomenal data collection by LRO's seven powerful instruments continues to contribute to our understanding of the Moon, as NASA carries forward with plans to return humans to lunar soil in collaboration with commercial and international partners. This ongoing legacy of exploration and discovery holds the promise of bringing back new knowledge and opportunities from our closest celestial neighbor.