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Int’l Payload Laser Retroreflector Deployed on Moon's Far Side by Chang’e-6 Mission

Jun 25, 2024

On June 2, 2024, the Chang’e-6 lander-ascender combination successfully touched down in the South Pole-Aitken Basin on the far side of the moon. This historic milestone was followed by another remarkable achievement on June 25, when the sample-return capsule successfully landed in Siziwang Banner, Inner Mongolia, China. This mission marks the first-time humanity has successfully returned samples from the far side of the moon.

A notable aspect of the Chang’e-6 mission is the international collaboration. Among the international payloads onboard is the laser retroreflector INRRI (INstrument for landing-Roving laser Retroreflector Investigations), a joint development by the National Laboratory of Frascati, National Institute for Nuclear Physics (INFN-LNF) and the Planetary Mapping and Remote Sensing Laboratory from the Aerospace Information Research Institute (AIR), Chinese Academy of Sciences (CAS). Mounted on the top panel of the Chang’e-6 lander, and successfully deployed on the far side of the moon, INRRI, which functions as a mirror for laser beams, aims to be the first laser retroreflector absolute control point on the moon’s far side. It will provide support for high-precision positioning on the lunar surface and the orbit determination and navigation of lunar orbiters. 

INRRI, capable of reflecting light from the visible to near-infrared wavelength, is built to work without any power source and to survive the harsh surface conditions on the moon for a long time. Through long-term laser ranging observations of INRRI by lunar orbiters, scientists expect to gather valuable data that will help refine lunar reference frame and improve navigation and positioning on the lunar surface.

The cooperation for INRRI between the Chinese and Italian teams began in 2015, formalized by a letter of intent for strategic cooperation in 2018 and a subsequent scientific-technical agreement for the Chang’e-6 mission. Professor DI Kaichang at AIR is the Principal Investigator (PI) on the Chinese side, and Dr. Simone Dell’Agnello serves as the PI for the Italian side. 

AIR scientists contributed to the overall design, interface design, environmental simulation tests and coordination for the mission. The cooperation is set to continue, focusing on lunar exploration and multidisciplinary applications of laser retroreflectors.

In addition to the INRRI contribution, AIR scientists were engaged in high-resolution topographic and geomorphologic analyses of the Chang’e-6 landing area. Their work provided crucial data that helped the China Academy of Space Technology choose the optimal landing site. 

Furthermore, the AIR team developed software for high-precision visual localization and 3D mapping, which was used at the Beijing Aerospace Control Center for teleoperations. It helped precisely locate the landing point, assess sampling points, and provide mapping support during teleoperation tasks.