NASA has delivered a retroreflector array to ESA that will allow the Lunar Pathfinder mission to be pinpointed by laser ranging stations back on Earth as it orbits the Moon. Such centimetre level laser measurements will serve as an independent check on the spacecraft as it fixes its position using Galleo and GPS signals from an unprecedented 400 000 km away from Earth – proving the concept of lunar satnav while also relaying telecommunications ahead of ESA’s dedicated Moonlight initiative.
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Source: ESA Space News