January 19, 2024

The Laser Retroreflector Array (LRA) on the Chandrayaan-3 lander has begun serving as a fiducial point points (precisely located markers for reference) on the moon. NASA's Lunar Reconnaissance Orbiter (LRO) achieved a laser range measurement using the LRA by successfully detecting signals reflected by it on December 12, 2023. The ranging utilized the Lunar Orbiter Laser Altimeter (LOLA) on the LRO. The observation occurred during lunar night time, with the LRO ascending to the east of Chandrayaan-3.

NASA’s LRA was accommodated on the Vikram lander under international collaboration. It comprises eight corner-cube retroreflectors on a hemispherical support structure. This array facilitates laser ranging from various directions by any orbiting spacecraft with suitable instrument. The passive optical instrument, weighing about 20 grams, is designed to last for decades on the lunar surface. Landed near the lunar south pole on August 23, 2023, Chandrayaan-3’s Vikram lander has been accessible for LOLA measurements since then.

While several LRAs have been deployed on the Moon since the beginning of lunar exploration, the LRA on Chandrayaan-3 is a miniature version and is the only one available near south pole currently. NASA’s LRA on Chandrayaan-3’s Vikram lander will continue to serve as a long-term geodetic station and a location marker on the lunar surface, benefitting current and future lunar missions. These measurements, apart from helping in precise determination of spacecraft’s orbital position, will help refine the lunar geodetic frame, revealing insights into the Moon's dynamics, internal structure, and gravitational anomalies.

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