Editing Retroreflector (section)

===In space===
====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>

====On Mars====
A similar device, the [[Laser retroreflector array|Laser Retroreflector Array]] (LaRA), has been incorporated in the Mars [[Perseverance (rover)|''Perseverance'' rover]]. The retroreflector was designed by the [[National Institute for Nuclear Physics]] of Italy, which built the instrument on behalf of the [[Italian Space Agency]].
[[File:PIA24097-MarsPerseveranceRover-LaRA-20200928.jpg|thumb|right|200px|Mars [[Perseverance (rover)|''Perseverance'' rover]] - LaRA - (artwork)]]

====In satellites{{anchor|In Earth orbit}}====
{{Further|Satellite laser ranging}}

Many [[artificial satellites]] carry retroreflectors so they can be tracked from [[ground stations]]. Some satellites were built solely for laser ranging.
[[LAGEOS]], or Laser Geodynamics Satellites, are a series of scientific research satellites designed to provide an orbiting laser ranging benchmark for geodynamical studies of the Earth.<ref>{{cite journal |last1=Pearlman |first1=M. |last2=Arnold |first2=D. |last3=Davis |first3=M. |last4=Barlier |first4=F. |last5=Biancale |first5=R. |last6=Vasiliev |first6=V. |last7=Ciufolini |first7=I. |last8=Paolozzi |first8=A. |last9=Pavlis |first9=E. C. |last10=Sośnica |first10=K. |last11=Bloßfeld |first11=M. |title=Laser geodetic satellites: a high-accuracy scientific tool |journal=Journal of Geodesy |date=November 2019 |volume=93 |issue=11 |pages=2181–2194 |doi=10.1007/s00190-019-01228-y|bibcode=2019JGeod..93.2181P |s2cid=127408940 }}</ref> There are two LAGEOS spacecraft: LAGEOS-1<ref>[https://ilrs.cddis.eosdis.nasa.gov/missions/satellite_missions/current_missions/lag1_general.html NASA.gov]</ref> (launched in 1976), and LAGEOS-2 (launched in 1992). They use cube-corner retroreflectors made of fused silica glass. As of 2020, both LAGEOS spacecraft are still in service.<ref>{{cite journal |last1=Zajdel |first1=R. |last2=Sośnica |first2=K. |last3=Drożdżewski |first3=M. |last4=Bury |first4=G. |last5=Strugarek |first5=D. |title=Impact of network constraining on the terrestrial reference frame realization based on SLR observations to LAGEOS |journal=Journal of Geodesy |date=November 2019 |volume=93 |issue=11 |pages=2293–2313 |doi=10.1007/s00190-019-01307-0|bibcode=2019JGeod..93.2293Z |doi-access=free }}</ref> Three [[Starshine (satellite)|STARSHINE]] satellites equipped with retroreflectors were launched beginning in 1999. The [[LARES (satellite)|LARES]] satellite was launched on February 13, 2012. (See also: [[List of laser ranging satellites]].)

Other satellites include retroreflectors for orbit calibration<ref>{{cite journal |last1=Kazmierski |first1=Kamil |last2=Sośnica |first2=Krzysztof |last3=Hadas |first3=Tomasz |date=2017-11-06 |title=Quality assessment of multi-GNSS orbits and clocks for real-time precise point positioning |journal=GPS Solutions |volume=22 |issue=1 |pages=11 |bibcode=2018GPSS...22...11K |doi=10.1007/s10291-017-0678-6 |doi-access=free}}</ref> and orbit determination,<ref>{{cite journal |last1=Bury |first1=Grzegorz |last2=Sośnica |first2=Krzysztof |last3=Zajdel |first3=Radosław |date=2018-04-19 |title=Multi-GNSS orbit determination using satellite laser ranging |journal=Journal of Geodesy |volume=93 |issue=12 |pages=2447–2463 |bibcode=2019JGeod..93.2447B |doi=10.1007/s00190-018-1143-1 |doi-access=free}}</ref> such as in [[satellite navigation]] (e.g., all [[Galileo satellites]],<ref>{{cite journal |last1=Sośnica |first1=Krzysztof |last2=Prange |first2=Lars |last3=Kaźmierski |first3=Kamil |last4=Bury |first4=Grzegorz |last5=Drożdżewski |first5=Mateusz |last6=Zajdel |first6=Radosław |last7=Hadas |first7=Tomasz |title=Validation of Galileo orbits using SLR with a focus on satellites launched into incorrect orbital planes |journal=Journal of Geodesy |date=February 2018 |volume=92 |issue=2 |pages=131–148 |doi=10.1007/s00190-017-1050-x|bibcode=2018JGeod..92..131S |doi-access=free }}</ref> most [[GLONASS satellites]],<ref>{{cite journal |last1=Zajdel |first1=Radosław |title=A New Online Service for the Validation of Multi-GNSS Orbits Using SLR |journal=Remote Sensing |date=14 October 2017 |volume=9 |issue=10 |pages=1049 |doi=10.3390/rs9101049|bibcode=2017RemS....9.1049Z |doi-access=free }}</ref> [[Indian Regional Navigation Satellite System|IRNSS satellites]],<ref>{{Cite web|url=https://ilrs.cddis.eosdis.nasa.gov/missions/satellite_missions/current_missions/irns_reflector.html|title=IRNSS: Reflector Information|website=ilrs.cddis.eosdis.nasa.gov|archive-url=https://web.archive.org/web/20190325175546/https://ilrs.cddis.eosdis.nasa.gov/missions/satellite_missions/current_missions/irns_reflector.html|archive-date=2019-03-25|access-date=2019-03-25}}</ref> [[BeiDou]],<ref>{{cite journal |last1=Sośnica |first1=Krzysztof |last2=Zajdel |first2=Radosław |last3=Bury |first3=Grzegorz |last4=Bosy |first4=Jarosław |last5=Moore |first5=Michael |last6=Masoumi |first6=Salim |title=Quality assessment of experimental IGS multi-GNSS combined orbits |journal=GPS Solutions |date=April 2020 |volume=24 |issue=2 |pages=54 |doi=10.1007/s10291-020-0965-5|doi-access=free |bibcode=2020GPSS...24...54S }}</ref> [[QZSS]],<ref>{{cite journal |last1=Sośnica |first1=K. |last2=Bury |first2=G. |last3=Zajdel |first3=R. |last4=Strugarek |first4=D. |last5=Drożdżewski |first5=M. |last6=Kazmierski |first6=K. |title=Estimating global geodetic parameters using SLR observations to Galileo, GLONASS, BeiDou, GPS, and QZSS |journal=Earth, Planets and Space |date=December 2019 |volume=71 |issue=1 |pages=20 |doi=10.1186/s40623-019-1000-3|bibcode=2019EP&S...71...20S |doi-access=free }}</ref> and two [[GPS satellites]]<ref>{{cite journal |last1=Sośnica |first1=Krzysztof |last2=Thaller |first2=Daniela |last3=Dach |first3=Rolf |last4=Steigenberger |first4=Peter |last5=Beutler |first5=Gerhard |last6=Arnold |first6=Daniel |last7=Jäggi |first7=Adrian |title=Satellite laser ranging to GPS and GLONASS |journal=Journal of Geodesy |date=July 2015 |volume=89 |issue=7 |pages=725–743 |doi=10.1007/s00190-015-0810-8|bibcode=2015JGeod..89..725S |doi-access=free }}</ref>) as well as in [[satellite gravimetry]] ([[GOCE]]<ref>{{cite journal |last1=Strugarek |first1=Dariusz |last2=Sośnica |first2=Krzysztof |last3=Jäggi |first3=Adrian |title=Characteristics of GOCE orbits based on Satellite Laser Ranging |journal=Advances in Space Research |date=January 2019 |volume=63 |issue=1 |pages=417–431 |doi=10.1016/j.asr.2018.08.033|bibcode=2019AdSpR..63..417S |s2cid=125791718 }}</ref>) [[satellite altimetry]] (e.g., [[TOPEX/Poseidon]], [[Sentinel-3]]<ref>{{cite journal |last1=Strugarek |first1=Dariusz |last2=Sośnica |first2=Krzysztof |last3=Arnold |first3=Daniel |last4=Jäggi |first4=Adrian |last5=Zajdel |first5=Radosław |last6=Bury |first6=Grzegorz |last7=Drożdżewski |first7=Mateusz |title=Determination of Global Geodetic Parameters Using Satellite Laser Ranging Measurements to Sentinel-3 Satellites |journal=Remote Sensing |date=30 September 2019 |volume=11 |issue=19 |pages=2282 |doi=10.3390/rs11192282|bibcode=2019RemS...11.2282S |doi-access=free }}</ref>).
Retroreflectors can also be used for inter-satellite laser ranging instead of ground-tracking (e.g., [[GRACE-FO]]).<ref>{{cite web |last=Schwarz |first=Oliver |date=2016-01-21 |title=GRACE FO Laser Ranging Interferometer |url=http://spacetech-i.com/products/optical-instruments/grace-fo-laser-ranging-interferometer |url-status=dead |archive-url=https://web.archive.org/web/20191206085105/https://spacetech-i.com/products/optical-instruments/grace-fo-laser-ranging-interferometer |archive-date=2019-12-06 |access-date=2018-04-06 |website=SpaceTech GmbH |language=en}}</ref>

The [[BLITS|BLITS (Ball Lens In The Space) spherical retroreflector satellite]] was placed into orbit as part of a September 2009 Soyuz launch<ref>{{Cite web |last1=Zak |first1=Anatoly |last2=Günes |first2=S. |date=2007-04-25 |title=Space exploration in 2009 |url=http://www.russianspaceweb.com/2009.html |url-status=live |archive-url=https://web.archive.org/web/20240115053452/https://www.russianspaceweb.com/2009.html |archive-date=2024-01-15 |access-date=2024-01-15 |website=RussianSpaceWeb.com |language=en}}</ref> by the [[Federal Space Agency of the Russian Federation|Federal Space Agency of Russia]] with the assistance of the [[International Laser Ranging Service]], an independent body originally organized by the [[International Association of Geodesy]], the [[International Astronomical Union]], and international committees.<ref>{{cite web |last=Tyahla |first=Lori J. |date=2013-02-20 |title=ILRS Missions: BLITS |url=http://ilrs.gsfc.nasa.gov/missions/satellite_missions/current_missions/blit_general.html |url-status=dead |archive-url=https://web.archive.org/web/20130220215607/http://ilrs.gsfc.nasa.gov/missions/satellite_missions/current_missions/blit_general.html |archive-date=2013-02-20 |access-date=2013-02-20 |website=International Laser Ranging Service |language=en}}</ref> The ILRS central bureau is located at the United States' [[Goddard Space Flight Center]].
The reflector, a type of [[Luneburg lens]], was developed and manufactured by the Institute for Precision Instrument Engineering (IPIE) in Moscow. The mission was interrupted in 2013 after a collision with [[space debris]].<ref name="EOportal">{{cite web|title=BLITS (Ball Lens In The Space)
 |url=https://directory.eoportal.org/web/eoportal/satellite-missions/b/blits
 |publisher=[[ESA]], Earth Observation portal}}</ref><ref>{{cite web |last=Blau |first=Patrick |date=2013-03-09 |title=Russian BLITS Satellite hit by Space Debris |url=http://www.spaceflight101.net/blits-satellite-collision-january-2013.html |url-status=usurped |archive-url=https://archive.today/20161005043844/http://www.spaceflight101.net/blits-satellite-collision-january-2013.html |archive-date=2016-10-05 |access-date=2020-04-16 |website=Spaceflight101: Space News and Beyond |language=en}}</ref>{{cbignore|bot=InternetArchiveBot}}