Editing Retroreflector (section)

====On the Moon====
{{Main|List of retroreflectors on the Moon|Lunar Laser Ranging Experiment}}
[[Image:Apollo 11 Lunar Laser Ranging Experiment.jpg|thumb|200px|The Apollo 11 Lunar Laser Ranging Experiment]]

[[Astronaut]]s on the [[Apollo 11]], [[Apollo 14|14]], and [[Apollo 15|15]] missions left retroreflectors on the [[Moon]] as part of the [[Lunar Laser Ranging Experiment]]. The [[Soviet Union|Soviet]] ''[[Lunokhod 1]]'' and ''[[Lunokhod 2]]'' rovers also carried smaller arrays. Reflected signals were initially received from ''Lunokhod 1'', but no return signals were detected from 1971 until 2010, at least in part due to some uncertainty in its location on the Moon. In 2010, it was found in [[Lunar Reconnaissance Orbiter]] photographs and the retroreflectors have been used again. ''Lunokhod 2's'' array continues to return signals to Earth.<ref>[http://ilrs.gsfc.nasa.gov/docs/williams_lw13.pdf NASA.gov]</ref> Even under good viewing conditions, only a single reflected photon is received every few seconds. This makes the job of filtering laser-generated photons from naturally occurring photons challenging.<ref>{{cite web|url=http://eclipse.gsfc.nasa.gov/SEhelp/ApolloLaser.html |title=NASA - Accuracy of Eclipse Predictions |publisher=eclipse.gsfc.nasa.gov |access-date=2015-08-15}}</ref>

[[Chandrayaan-3#Vikram lander|Vikram lander]] of [[Chandrayaan-3]] left Laser Retroreflector Array (LRA) instrument supplied by [[NASA]]'s [[Goddard Space Flight Center]] as part of international collaboration with [[ISRO]]. On 12 December 2023, [[Lunar Reconnaissance Orbiter]] was successfully able to detect transmitted laser pulses from Vikram lander.<ref name=":12">{{Cite news |date=2024-01-19 |title=NASA spacecraft pings India's Chandrayaan-3 lander on the moon |url=https://www.thehindu.com/sci-tech/science/nasa-spacecraft-pings-indias-chandrayaan-3-lander-on-the-moon/article67755589.ece |access-date=2024-01-22 |work=The Hindu |language=en-IN |issn=0971-751X}}</ref>