MoonLIGHT (Moon Laser Instrumentation for General relativity High accuracy Tests) is alaser retroreflector developed as a collaboration primarily between theUniversity of Maryland in the United States, and the ItalianNational Institute for Nuclear Physics -National Laboratories of Frascati (INFN-LNF) to complement and expand on theLunar Laser Ranging experiment started with theApollo Program in 1969.
MoonLIGHT was planned to be launched in July 2020 as a secondary payload on theMX-1E lunar lander built by the private companyMoon Express. However, the launch of the MX-1E has been cancelled. In 2018 INFN proposed to theEuropean Space Agency (ESA) the MoonLIGHT Pointing Actuators (MPAc) project and was contracted by ESA to deliver it. MPAc is an INFN development for ESA, with auxiliary support by the Italian Space Agency (ASI) for prototyping work. In 2021, ESA agreed withNASA to launch MPAc with aCommercial Lunar Payload Services (CLPS) mission.Nova-C, the lander on which MPAc will be integrated, is designed byIntuitive Machines and the landing site isReiner Gamma. The expected launch date of the Nova-C mission carrying the instrument,IM-3, is in 2026.[1][2]
Laser Ranging is a technique used to perform accurate precision distance measurements between alaser and an optical target, called aretroreflector. Since 1969, it is possible to performLunar Laser Ranging (LLR) measurements thanks to theCube Corner Retroreflector (CCR) arrays placed on the lunar surface by theApollo andLuna missions. The principle of this laser ranging is based on laser pulses sent from a telescope on Earth to the retroreflector array on the Moon. The retroreflector (mirrors) send the pulse straight back to the originating telescope where the round trip time—and therefore the exact distance—is recorded. The reflector arrays are designed to allow more accurate measurements from Earth that will increase lunar mapping accuracy, will test principles of Einstein'sgeneral theory of relativity, and other theories of gravity. Researchers think these studies may also help understand the nature ofdark energy.[3][4]
MoonLIGHT is a single 100 mm-large CCR developed as a collaboration primarily between theUniversity of Maryland and the ItalianNational Institute for Nuclear Physics -National Laboratories of Frascati (INFN-LNF) .[3] Additional partners and collaborators include theItalian Space Agency'sMatera Laser Ranging Observatory, as well as others laser ranging observatories and research institutes.[3]
This experiment will complement and advance the retroreflector experiments begun withApollo 11 in 1969.[3] The team claims to have developed a new approach and technology that would improve the ranging accuracy up to a factor of 100[4] (thus at a millimeter level) by using new technology and methods to correct for libration and the thermal behavior and the optical performance.[5][how?]
The experiment and agreement between the collaborators was announced on 15 May 2015.[3]
The reflector was planned to be a secondary payload on theMX-1E lunar lander built byMoon Express,[6] which was planned to be launched in 2020 with anElectron rocket.[6] An unrelated planned science payload on the same lander was theInternational Lunar Observatory.[7] The MX-1E lander was planned to land on theMalapert Mountain, a 5 km tall peak in theAitken Basin region that has an uninterrupted direct line of sight to Earth.[8] The launch contract between Moon Express and Rocket Lab (manufacturer of Electron) was canceled sometime before February 2020. Moon Express does not, as of February 2020, anymore plan to launch MX-1E on an Electron rocket, thus leavingMX-1E and all its science payloads without a carrier rocket.[9]
In 2018 INFN proposed toESA the MoonLIGHT Pointing Actuators (MPAc) project, able to perform automatic pointing operation of MoonLIGHT, on the contrary to the ApolloCCR arrays that were manually arranged by the astronauts. In 2019 ESA chose MPAc among 135 eligible scientific project proposals and, in 2021, ESA agreed with NASA to launch MPAc with aCommercial Lunar Payload Services (CLPS) mission.Nova-C, the lander on which MPAc will be integrated, is designed byIntuitive Machines and the expected launch date is in 2026.[1] The landing site isReiner Gamma, a lunar swirl on the western edge of the Moon, as seen from Earth.[2][10][11][12]