View source for Laser communication in space

{{Short description|Communication using lasers in outer space}}
{{Use British English|date=December 2021}}
{{Use dmy dates|date=December 2021}}

[[File:Two solar-powered satellites communicating optically in space via lasers.svg|thumb|upright=1.0|right|A diagram showing two solar-powered satellites communicating optically in space via lasers.]]{{Cleanup rewrite|date=June 2022}}
'''Laser communication in space''' is the use of [[free-space optical communication]] in [[outer space]]. Communication may be fully in space (an '''inter-satellite laser link''') or in a ground-to-satellite or satellite-to-ground application. The main advantage of using laser communications over [[Radio|radio waves]] is increased [[Bandwidth (computing)|bandwidth]], enabling the transfer of more data in less time. 
 
In outer space, the communication range of free-space optical communication is currently of the order of hundreds of thousands of kilometers.<ref>{{cite web|title=LLCD: 2013-2014|publisher=National Aeronautics and Space Agency|date=June 15, 2018 |url=https://www.nasa.gov/directorates/heo/scan/opticalcommunications/llcd/|access-date=August 27, 2022}}</ref> Laser-based optical communication has been demonstrated between the Earth and Moon and it has the potential to bridge interplanetary distances of millions of kilometers, using optical telescopes as [[beam expander]]s.<ref>{{cite web|title=Optisk kommunikation i deep space – Et feasibilitystudie i forbindelse med Bering-missionen|date=October 27, 2003|author=Steen Eiler Jørgensen|publisher=Dansk Rumforskningsinstitut|url=http://silicium.dk/pdf/speciale.pdf|access-date=June 28, 2011}} (Danish) Optical Communications in Deep Space, University of Copenhagen</ref>

== Demonstrations and tests ==
=== Before 1990 ===
On 20 January 1968, the television camera of the [[Surveyor 7]] lunar lander successfully detected two [[Ion laser|argon lasers]] from [[Kitt Peak National Observatory]] in [[Arizona]] and [[Table Mountain Observatory]] in [[Wrightwood, California]].<ref>{{cite web|url=http://www.w7ftt.net/laser2.html|title=Argon Laser as Seen from the Moon}}</ref>

=== 1991–2000 ===
In 1992, the [[Galileo (spacecraft)|''Galileo'']] probe proved successful one-way detection of laser light from Earth as two ground-based lasers were seen from {{cvt|6000000|km}} by the out-bound probe.<ref>{{cite news|url=https://www.space.com/534-nasa-test-laser-communications-mars-spacecraft.html|title=NASA To Test Laser Communications With Mars Spacecraft|date=November 15, 2004|first=Brian|last=Berger |publisher=Space.com|access-date=2018-02-24}}</ref>

The first successful laser-communication link from space was carried out by [[Japan]] in 1995 between the [[NASDA]]'s [[ETS-VI]] GEO satellite and the {{cvt|1.5|m}} ''[[National Institute of Information and Communications Technology]] (NICT)'''s optical ground station in [[Tokyo]] achieving 1 [[Data-rate units|Mbit/s]].<ref>{{cite conference |title=Performance evaluation of laser communication equipment onboard the ETS-VI satellite |publisher=SPIE |doi=10.1117/12.238434|book-title=Free-Space Laser Communication Technologies VIII |year=1996 |editor-last1=Mecherle |editor-first1=G. Stephen |last1=Araki |first1=Kenichi |last2=Arimoto |first2=Yoshinori |last3=Shikatani |first3=Motokazu |last4=Toyoda |first4=Masahiro |last5=Toyoshima |first5=Morio |last6=Takahashi |first6=Tetsuo |last7=Kanda |first7=Seiji |last8=Shiratama |first8=Koichi |volume=2699 |page=52 }}</ref>

=== 2001–2010 ===
In November 2001, the world's first laser intersatellite link was achieved in space by the [[European Space Agency]] (ESA) satellite [[Artemis (satellite)|Artemis]], providing an optical data transmission link with the [[CNES]] [[Earth observation satellite]] [[SPOT (satellite)|SPOT 4]].<ref>{{cite web |url=http://www.esa.int/Our_Activities/Telecommunications_Integrated_Applications/A_world_first_Data_transmission_between_European_satellites_using_laser_light|title=A world first: Data transmission between European satellites using laser light|date=22 November 2001|access-date=5 September 2015}}</ref> Achieving 50 [[Data-rate units|Mbps]] across {{cvt|40000|km}}, the distance of a LEO-GEO link.<ref name=ESA-OCS-1997>{{cite web
|url=http://www.esa.int/esapub/bulletin/bullet91/b91lutz.htm|title=Optical Communications in Space|date=August 1997|publisher=ESA}}</ref> Since 2005, ARTEMIS has been relaying two-way optical signals from ''Kirari'', the Japanese [[Optical Inter-orbit Communications Engineering Test Satellite]].<ref>{{cite web|url=http://telecom.esa.int/telecom/www/object/index.cfm?fobjectid=27945|title=Another world first for ARTEMIS: a laser link with an aircraft|date=19 December 2006|publisher=ESA|archive-url=https://web.archive.org/web/20090903020645/http://telecom.esa.int/telecom/www/object/index.cfm?fobjectid=27945|archive-date=3 September 2009}}</ref>

In May 2005, a two-way distance record for communication was set by the [[Mercury (planet)|Mercury]] [[laser altimeter]] instrument aboard the ''[[MESSENGER]]'' spacecraft. This diode-pumped infrared [[neodymium laser]], designed as a laser altimeter for a Mercury orbit mission, was able to communicate across a distance of {{cvt|24000000|km}}, as the craft neared Earth on a fly-by.<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/science/nature/4587580.stm|title=Space probe breaks laser record: A spacecraft has sent a laser signal to Earth from 24 million km away in interplanetary space|date=January 6, 2006|access-date=June 28, 2011|publisher=BBC News}}</ref>

In 2006, Japan carried out the first LEO-to-ground laser-communication downlink from JAXA's [[OICETS]] LEO satellite and NICT's optical ground station.<ref>{{cite journal |url=https://www.sciencedirect.com/science/article/abs/pii/S0094576511003808|title=Acta Astronautica "Results of Kirari optical communication demonstration experiments with NICT optical ground station (KODEN) aiming for future classical and quantum communications in space"|journal=Acta Astronautica |date=May 2012 |volume=74 |pages=40–49 |doi=10.1016/j.actaastro.2011.12.020 |access-date=18 February 2020|last1=Toyoshima |first1=Morio |last2=Takenaka |first2=Hideki |last3=Shoji |first3=Yozo |last4=Takayama |first4=Yoshihisa |last5=Koyama |first5=Yoshisada |last6=Kunimori |first6=Hiroo }}</ref>

In 2008, the ESA used laser communication technology designed to transmit 1.8 Gbit/s across {{cvt|40000|km}}, the distance of a LEO-GEO link. Such a terminal was successfully tested during an in-orbit verification using the German radar satellite [[TerraSAR-X]] and the American [[Near Field Infrared Experiment]] (NFire) satellite. The two Laser Communication Terminals (LCT)<ref>[http://www.tesat.de/en/divisions/laser-products/laser-communication-terminals Laser Communication Terminals: An Overview] {{webarchive |url=https://web.archive.org/web/20160911143720/http://www.tesat.de/en/divisions/laser-products/laser-communication-terminals|date=2016-09-11}}</ref> used during these tests were built by the German company [[Tesat-Spacecom]],<ref name="Tesat-Spacecom Website2">[http://www.tesat.de/en Tesat-Spacecom Website]</ref> in cooperation with the German Aerospace Center (DLR).<ref name="TerraSAR-X NFIRE test2">[http://www.dlr.de/en/desktopdefault.aspx/tabid-78/7420_read-14120/ TerraSAR-X NFIRE test]</ref>

=== 2011–2020 ===
[[File:LADEE's_LLCD_optical_module_rendering.jpg|thumb|upright=1.0|right|Depiction of the optical module of the LLCD]]
[[File:OPALS_laser_beams_data_to_Earth.jpg|thumb|upright=1.0|right|The successful [[OPALS]] experiment]]

In January 2013, [[NASA]] used lasers to beam an image of the [[Mona Lisa]] to the [[Lunar Reconnaissance Orbiter]] (LRO) roughly {{cvt|390000|km}} away at night from the Next Generation Satellite Laser Ranging (NGSLR) Station at NASA's Earth-based [[Goddard Space Flight Center]]. To compensate for atmospheric interference, an error correction code algorithm similar to that used in [[Compact disc|CD]]s was implemented.<ref>{{cite news|url=https://newsfeed.time.com/2013/01/21/nasa-beams-mona-lisa-image-into-space/|title=NASA Beams Mona Lisa Image Into Space|last=Peckham|first=Matt|date=January 21, 2013|access-date=22 January 2013|publisher=Time}}</ref>

In September 2013, a laser communication system was one of four science instruments launched with the NASA [[LADEE]] (Lunar Atmosphere and Dust Environment Explorer) mission. After a month-long transit to the [[Moon]] and a 40-day spacecraft checkout, daytime laser communications experiments were performed over three months during late 2013 and early 2014.<ref name="st201309072">{{cite news |url=http://www.toledoblade.com/Nation/2013/09/07/NASA-launches-robotic-explorer-to-moon-from-Va-trouble-develops-early-in-much-viewed-flight.html|title=NASA launches robotic explorer to moon from Va.; trouble develops early in much-viewed flight|date=2013-09-07|newspaper=Toledo Blade|access-date=2016-05-15|archive-url=https://web.archive.org/web/20160515171256/http://www.toledoblade.com/Nation/2013/09/07/NASA-launches-robotic-explorer-to-moon-from-Va-trouble-develops-early-in-much-viewed-flight.html|archive-date=2016-05-15|url-status=live|agency=Associated Press}}</ref> Initial data returned from the [[Lunar Laser Communication Demonstration]] (LLCD) equipment on LADEE set a space [[Bandwidth (signal processing)|communication bandwidth]] record in October 2013 when early tests using a [[Pulsed laser|pulsed laser beam]] to transmit data over the {{cvt|385000|km}} between the Moon and Earth passed data at a "record-breaking [[Downlink|download]] rate of 622 megabits per second (Mbps)",<ref name="pa201310232">{{cite news |url=http://www.parabolicarc.com/2013/10/22/nasa-laser-system-sets-record-data-transmissions-moon/|title=NASA Laser System Sets Record with Data Transmissions From Moon|last=Messier|first=Doug|date=2013-10-23 |publisher=Parabolic Arc|access-date=2013-10-23}}</ref> and also demonstrated an error-free data [[Uplink|upload]] rate of 20&nbsp;Mbit/s from an Earth ground station to LADEE in [[lunar orbit]]. The LLCD is NASA's first attempt at two-way [[space communication]] using an [[Laser|optical laser]] instead of [[radio wave]]s, and is expected to lead to operational laser systems on NASA satellites in future years.<ref name="pa201310232"/>

In November 2013, laser communication from a jet platform [[Panavia Tornado|Tornado]] was successfully demonstrated for the first time. A laser terminal of the German company [[Mynaric]] (formerly ViaLight Communications) was used to transmit data at a rate of 1&nbsp;Gbit/s over a distance of 60&nbsp;km and at a flight speed of 800&nbsp;km/h in daylight. Additional challenges in this scenario were the fast flight maneuvers, strong vibrations, and the effects of atmospheric turbulence. The demonstration was financed by [[EADS|EADS Cassidian]] [[Germany]] and performed in cooperation with the [[German Aerospace Center|German Aerospace Center DLR]].<ref name="cassidian-pressemitteilung2">{{cite web|url=http://www.cassidian.com/en_US/web/guest/optical-data-link-successfully-demonstrated|title=Optical data link successfully demonstrated between fighter plane and ground station|last=Belz|first=Lothar|date=2013-12-19|archive-url=https://web.archive.org/web/20131230233648/http://www.cassidian.com/en_US/web/guest/optical-data-link-successfully-demonstrated|archive-date=2013-12-30}}</ref><ref name="vialight-pressemitteilung2">[http://vialight.de/index.php?id=180 Extreme Test for the ViaLight Laser Communication Terminal MLT-20 – Optical Downlink from a Jet Aircraft at 800 km/h, December 2013]</ref><ref name="DLR-pressemitteilung2">{{cite web|url=http://dlr.de/dlr/desktopdefault.aspx/tabid-10293/427_read-9050/year-all/#gallery/8366 |title=Laserkommunikation zwischen Jet und Bodenstation}}</ref>

In November 2014, the first ever use of gigabit laser-based communication as part of the [[European Data Relay System]] (EDRS) was carried out.<ref>{{cite web |url=https://airbusdefenceandspace.com/newsroom/news-and-features/first-image-download-over-new-gigabit-laser-connection-in-space/|title=First image download over new gigabit laser connection in space|access-date=3 December 2014|archive-url=https://web.archive.org/web/20150415081425/http://airbusdefenceandspace.com/newsroom/news-and-features/first-image-download-over-new-gigabit-laser-connection-in-space/|archive-date=15 April 2015}}</ref> Further system and operational service demonstrations were carried out in 2014. Data from the EU [[Sentinel-1A]] satellite in LEO was transmitted via an optical link to the ESA-Inmarsat [[Alphasat]] in GEO and then relayed to a ground station using a conventional [[Ka band|Ka-band]] downlink. The new system can offer speeds up to 7.2&nbsp;Gbit/s.<ref>{{cite web |url=http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-1/Laser_link_offers_high-speed_delivery|title=Laser link offers high-speed delivery|date=28 November 2014|publisher=ESA|access-date=5 December 2014}}</ref> The Laser terminal on Alphasat is called TDP-1 and is still regularly used for tests. The first EDRS terminal (EDRS-A) for productive use has been launched as a payload on the Eutelsat EB9B spacecraft and became active in December 2016.<ref>{{cite web|url=https://www.esa.int/Our_Activities/Telecommunications_Integrated_Applications/EDRS/Start_of_service_for_Europe_s_SpaceDataHighway |title=Start of service for_Europe's Space Data Highway|date=23 November 2016|publisher=ESA|access-date=11 April 2019}}</ref> It routinely downloads high-volume data from the Sentinel 1A/B and Sentinel 2A/B spacecraft to ground. So far (April 2019) more than 20000 links (11 [[Petabit|PBit]]) have been performed.<ref>{{cite web |url=https://www.esa.int/Our_Activities/Telecommunications_Integrated_Applications/First_satellite_in_European_SpaceDataHighway_forges_20_000_successful_laser_links|title=European Space Data Highway forges 20000 successful laser links|date=2 April 2019|publisher=ESA|access-date=5 April 2019}}</ref>
As of May 2023, EDRS has over one million minutes of communications<ref>{{Cite web |date=2023-04-25 |title=EDRS reached 1,000,000 minutes of communications! |url=https://securecommunications.airbus.com/en/news/edrs-is-reaching-1000000-minutes-of-communications |access-date=2023-05-04 |website=[[Airbus]] |language=en}}</ref> with more than 50,000 successful inter-satellite links.<ref>{{Cite web |date=2021-06-24 |title=SpaceDataHighway reaches milestone of 50,000 successful laser connections |url=https://securecommunications.airbus.com/en/news/spacedatahighway-reaches-milestone-of-50000-successful-laser-connections |access-date=2023-05-04 |website=[[Airbus]] |language=en}}</ref><ref>{{Cite web |date=2022-09-18 |title=AUTO-TDS: ENABLING LASER COMMUNICATION NETWORKS TO AUTO DETECT INCOMING LINKS, SECURING CONNECTION AND AUTO-ROUTING THE DATA |url=https://www.researchgate.net/publication/364459515 |access-date=2023-05-04 |website=[[ResearchGate]] |language=en}}</ref>

In December 2014, NASA's [[Optical Payload for Lasercomm Science]] (OPALS) announced a breakthrough in space-to-ground laser communication, downloading at a speed of 400 megabits per second. The system is also able to re-acquire tracking after the signal is lost due to cloud cover.<ref>{{cite news|url=http://www.jpl.nasa.gov/news/news.php?feature=4402|title=OPALS: Light Beams Let Data Rates Soar|last=Landau |first=Elizabeth|date=9 December 2014|work=Jet Propulsion Laboratory|access-date=18 December 2014|publisher=NASA}} {{PD-notice}}</ref> The OPALS experiment was launched on 18 April 2014 to the [[International Space Station]] (ISS) to further test the potential for using a laser to transmit data to Earth from space.<ref>{{cite news|url=http://www.jpl.nasa.gov/news/news.php?release=2014-122|title=JPL Cargo Launched to Space Station|last1=L. Smith|first1=Stephanie|date=21 April 2014|work=Jet Propulsion Laboratory|access-date=2014-04-22|publisher=NASA|last2=Buck|first2=Joshua|last3=Anderson|first3=Susan}} {{PD-notice}}</ref>

The first LEO-to-ground lasercom demonstration using a Japanese [[Small satellite|microsatellite]] ([[SOCRATES (satellite)|SOCRATES]]) was carried out by NICT in 2014,<ref>{{cite journal |url=https://www.sciencedirect.com/science/article/abs/pii/S0094576516313194|title=Acta Astronautica "LEO-to-ground optical communications using SOTA (Small Optical TrAnsponder) – Payload verification results and experiments on space quantum communications"|pages=377–384 |access-date=2020-02-18|journal=Acta Astronautica|date=October 2017 |volume=139 |doi=10.1016/j.actaastro.2017.07.030 |last1=Carrasco-Casado |first1=Alberto |last2=Takenaka |first2=Hideki |last3=Kolev |first3=Dimitar |last4=Munemasa |first4=Yasushi |last5=Kunimori |first5=Hiroo |last6=Suzuki |first6=Kenji |last7=Fuse |first7=Tetsuharu |last8=Kubo-Oka |first8=Toshihiro |last9=Akioka |first9=Maki |last10=Koyama |first10=Yoshisada |last11=Toyoshima |first11=Morio |arxiv=1708.01592 |s2cid=115327702 }}</ref> and the first quantum-limited experiments from space were done by using the same satellite in 2016.<ref name="TakenakaCarrasco-Casado2017">{{cite journal|last1=Takenaka|first1=Hideki|last2=Carrasco-Casado|first2=Alberto|last3=Fujiwara|first3=Mikio|last4=Kitamura|first4=Mitsuo|last5=Sasaki|first5=Masahide |last6=Toyoshima|first6=Morio|display-authors=3|title=Satellite-to-ground quantum-limited communication using a 50-kg-class microsatellite|journal=Nature Photonics|volume=11|issue=8|year=2017|pages=502–508 |issn=1749-4885|doi=10.1038/nphoton.2017.107|arxiv=1707.08154|s2cid=118935026 }}</ref>

In February 2016, [[Google X]] announced to have achieved a stable laser communication connection between two [[High-altitude balloon|stratospheric balloons]] over a distance of {{cvt|100|km}} as part of [[Loon LLC|Project Loon]]. The connection was stable over many hours and during day and nighttime and reached a data rate of 155&nbsp;Mbit/s.<ref name=":02">{{cite news |url=https://www.wired.com/2016/02/google-shot-laser-60-miles-just-send-copy-real-genius/|title=Google Laser-Beams the Film ''Real Genius'' 60 Miles Between Balloons|publisher=Wired|date=24 February 2016 |first=Cade|last=Metz|access-date=2018-02-24}}</ref>

In June 2018, Facebook's Connectivity Lab (related to [[Facebook Aquila]]) was reported to have achieved a bidirectional 10 Gbit/s air-to-ground connection in collaboration with [[Mynaric]]. The tests were carried out from a conventional [[Cessna]] aircraft in {{cvt|9|km}} distance to the optical ground station. While the test scenario had worse platform vibrations, atmospheric turbulence and angular velocity profiles than a stratospheric target platform the uplink worked flawlessly and achieved 100% throughput at all times. The downlink throughput occasionally dropped to about 96% due to a non-ideal software parameter which was said to be easily fixed.<ref name="BI-Facebook">{{cite web|last1=Price|first1=Rob|title=Facebook tested plane-mounted lasers that fire super high-speed internet over California — here are the photos|url=https://www.msn.com/en-us/money/companies/facebook-tested-plane-mounted-lasers-that-fire-super-high-speed-internet-over-california-%E2%80%94-here-are-the-photos/ar-AAziD3w|archive-url=https://web.archive.org/web/20180629085509/http://www.msn.com/en-us/money/companies/facebook-tested-plane-mounted-lasers-that-fire-super-high-speed-internet-over-california-%E2%80%94-here-are-the-photos/ar-AAziD3w|archive-date=29 June 2018|publisher=Business Insider|date=29 June 2018|access-date=21 July 2018}}</ref>

In April 2020, the Small Optical Link for International Space Station (SOLISS) created by JAXA and [[Sony]] Computer Science Laboratories, established bidirectional communication between the ISS and a telescope of the [[National Institute of Information and Communications Technology]] of Japan.<ref>{{cite web|title=Small Optical Link for International Space Station (SOLISS) Succeeds in Bidirectional Laser Communication Between Space and Ground Station|url=https://global.jaxa.jp/press/2020/04/20200423-1_e.html|publisher=JAXA|date=April 23, 2020|access-date=7 August 2020}}</ref>

On 29 November 2020, Japan launched the inter-satellite optical data relay [[geostationary orbit]] satellite with high speed laser communication technology, named LUCAS (Laser Utilizing Communication System).<ref>{{cite web|title=「データ中継衛星」搭載のH2Aロケット43号機打ち上げ成功|url=https://www3.nhk.or.jp/news/html/20201129/k10012736931000.html|publisher=NHK|date=November 29, 2020|access-date=29 November 2020}}</ref><ref>{{cite web|title= 光衛星間通信システム（LUCAS|url=https://www.satnavi.jaxa.jp/project/lucas/|publisher=JAXA|date=October 30, 2020|access-date=29 November 2020}}</ref>

=== 2021–present ===
[[File:The-Video-NASA’s-Laser-Communications-Experiment-Streamed-From-Deep-Space.mpg|thumb|First video transmitted via laser from ''Psyche''. Uploaded before launch, the short ultra-high definition video features an orange tabby cat named Taters, the pet of a JPL employee, chasing a laser pointer, with overlayed graphics. The graphics illustrate several features from the tech demo, such as Psyche's orbital path, Palomar's telescope dome, and technical information about the laser and its data bit rate. Tater's heart rate, color, and breed are also on display.<ref>{{cite web |title=NASA's Tech Demo Streams First Video From Deep Space via Laser |url=https://www.jpl.nasa.gov/news/nasas-tech-demo-streams-first-video-from-deep-space-via-laser |website=NASA Jet Propulsion Laboratory (JPL) |access-date=22 December 2023}} {{PD-notice}}</ref>]]

In June 2021, the [https://www.sda.mil/ U.S. Space Development Agency] launched a two 12U [[CubeSat]]s aboard a [[SpaceX]] [[Falcon 9]] [[Transporter-2]] rideshare mission to [[Sun-synchronous orbit]]. The mission is expected to demonstrate laser communication links between the satellites and a remotely controlled [[MQ-9 Reaper]].<ref name=GA-Reaper>{{cite web|title=DoD space agency to launch laser communications experiments on SpaceX rideshare|url=https://spacenews.com/dod-space-agency-to-launch-laser-communications-experiments-on-spacex-rideshare/|publisher=SpaceNews|date=2021-06-02}}</ref>

On December 7, 2021, NASA's [[Laser Communications Relay Demonstration]] (LCRD) launched as part of USAF [[Space Test Program|STP-3]], to communicate between [[geosynchronous orbit]] and the Earth's surface.

In May 2022, [[TeraByte InfraRed Delivery]] (TBIRD) was launched (on [[PTD-3]]) and tested 100&nbsp;Gbit/s comms from 300 mile orbit to California.<ref>[https://www.spacedaily.com/reports/Communications_system_achieves_fastest_laser_link_from_space_yet_999.html ''Communications system achieves fastest laser link from space yet'']</ref>

Laser communications in deep space will be tested on the [[Psyche (spacecraft)|''Psyche'']] mission to the main-belt asteroid [[16 Psyche]], launched in 2023.<ref name="Greicius">{{cite web |url=https://www.nasa.gov/mission_pages/psyche/overview/index.html|title=Psyche Overview|last=Greicius|first=Tony|date=14 September 2017|publisher=Nasa|access-date=18 September 2017}} {{PD-notice}}</ref> The system is called [[Deep Space Optical Communications]] (DSOC),<ref name="DSOC2">[https://www.jpl.nasa.gov/news/news.php?feature=6967 Deep Space Communications via Faraway Photons] NASA, 18 October 2017 {{PD-notice}}</ref> and is expected to increase spacecraft communications performance and efficiency by 10 to 100 times over conventional means.<ref name="DSOC2"/><ref name="Greicius"/>In April 2024, the test was successfully completed with the Psyche spacecraft at a distance of 140 million miles.<ref>{{Cite web |date=2024-04-25 |title=NASA's Optical Comms Demo Transmits Data Over 140 Million Miles - NASA |url=https://www.nasa.gov/missions/psyche-mission/nasas-optical-comms-demo-transmits-data-over-140-million-miles/ |access-date=2024-04-27 |language=en-US}}</ref>

=== Future missions ===
Japan's National Institute of Information and Communications Technology (NICT) will demonstrate in 2022 the fastest bidirectional lasercom link between the geosynchronous orbit and the ground at 10&nbsp;Gbit/s by using the HICALI (High-speed Communication with Advanced Laser Instrument) lasercom terminal on board the ETS-9 (Engineering Test Satellite IX) satellite,<ref>{{cite book|chapter=Research and development on a hybrid high throughput satellite with an optical feeder link — Study of a link budget analysis|doi=10.1109/ICSOS.2017.8357424|isbn=978-1-5090-6511-0|title=2017 IEEE International Conference on Space Optical Systems and Applications (ICSOS)|year=2017|last1=Toyoshima|first1=Morio|last2=Fuse|first2=Tetsuharu|last3=Carrasco-Casado|first3=Alberto|last4=Kolev|first4=Dimitar R.|last5=Takenaka|first5=Hideki|last6=Munemasa |first6=Yasushi|last7=Suzuki|first7=Kenji|last8=Koyama|first8=Yoshisada|last9=Kubo-Oka|first9=Toshihiro|last10=Kunimori|first10=Hiroo|pages=267–271|s2cid=13714770}}</ref> as well as the first intersatellite link at the same high speed between a CubeSat in LEO and HICALI in GEO one year later.<ref>{{cite book|chapter=Intersatellite-Link Demonstration Mission between CubeSOTA (LEO CubeSat) and ETS9-HICALI (GEO Satellite)|doi=10.1109/ICSOS45490.2019.8978975|arxiv=2002.02791|bibcode=2020arXiv200202791C|isbn=978-1-7281-0500-0|last1=Carrasco-Casado|first1=Alberto|last2=Do|first2=Phong Xuan|last3=Kolev|first3=Dimitar |last4=Hosonuma|first4=Takayuki|last5=Shiratama|first5=Koichi|last6=Kunimori|first6=Hiroo|last7=Trinh|first7=Phuc V.|last8=Abe|first8=Yuma|last9=Nakasuka|first9=Shinichi|last10=Toyoshima|first10=Morio |title=2019 IEEE International Conference on Space Optical Systems and Applications (ICSOS)|pages=1–5|year=2020|s2cid=211059224}}</ref> {{As of|2024|May}}, a Full Trasceiver type terminal compatible for CubeSat has been designed and in development. CubeSOTA is expected to launch during the Japanese fiscal year 2025 with the terminal for "demonstrating various scenarios, including LEO–ground, LEO–HAPS, and LEO–LEO." CubeSOTA "will be the first in-orbit validation of the terminals."<ref>{{Cite journal |last1=Carrasco-Casado |first1=Alberto |last2=Shiratama |first2=Koichi |last3=Kolev |first3=Dimitar |last4=Ono |first4=Fumie |last5=Tsuji |first5=Hiroyuki |last6=Toyoshima |first6=Morio |date=2024-06-07 |title=Miniaturized Multi-Platform Free-Space Laser-Communication Terminals for Beyond-5G Networks and Space Applications |journal=Photonics |volume=11 |issue=6 |page=545 |doi=10.3390/photonics11060545|doi-access=free |bibcode=2024Photo..11..545C }}</ref>

[[LunaNet]] is a NASA and ESA project and proposed data network aiming to provide a “Lunar Internet“ for [[Cis-lunar space|cis-lunar]] spacecraft and installations. The specification for the system includes optical communications for links between the Earth and the Moon as well as for links between lunar satellites and the lunar surface.

== Commercial use ==
Corporations like [[SpaceX]], [[Facebook]] and [[Google]] and a series of [[NewSpace|startups]] are currently pursuing various concepts based on laser communication technology. The most promising commercial applications can be found in the interconnection of [[satellite]]s or [[High-altitude platform station|high-altitude platforms]] to build up high-performance optical [[Backbone network|backbone]] networks. Other applications include transmitting large amounts of data directly from a satellite, aircraft or [[unmanned aerial vehicle]] (UAV) to the ground.<ref>{{cite web |url=http://elib.dlr.de/49621/1/2006_SPIE_STROPEX_Horwath_Reprint.pdf|title=Broadband Backhaul Communication for Stratospheric Platforms: The Stratospheric Optical Payload Experiment (STROPEX)|author1=J. Horwath|author2=M. Knapek|date=July 21, 2006|publisher=SPIE|author3=B. Epple|author4=M. Brechtelsbauer}}</ref>

=== Operators ===
Multiple companies and government organizations want to use laser communication in space for [[satellite constellation]]s in [[low Earth orbit]] to provide global high-speed Internet access. Similar concepts are pursued for networks of aircraft and stratospheric platforms.

{| class="wikitable sortable"
|+
! Project
! width="400" |Project Concept
! Environment
! Scenario
! Data rate
! Total number of lasers deployed/anticipated
! Supplier
! Status
|-
|[[Starlink]]
|[[Satellite constellation|Satellite mega-constellation]] for global telecommunications
|LEO
|Space-to-space
|100 Gbit/s<ref>{{cite web|url=https://www.arcep.fr/actualites/actualites-et-communiques/detail/n/frequences-020622.html|title=Fréquences Après consultation publique, l'Arcep attribue une nouvelle autorisation d'utilisation de fréquences à Starlink (see ZIP file linked from article narrative)|date=2 Jun 2022|website=arcep.fr|access-date=March 18, 2023}}</ref>
|>1,000/>10,000
|[[SpaceX]] / [[Starlink]]
|Active since 2021<ref>{{cite web |title=Latest Starlink Satellites Equipped with Laser Communications, Musk Confirms - Via Satellite - |url=https://www.satellitetoday.com/broadband/2021/01/25/latest-starlink-satellites-equipped-with-laser-communications-musk-confirms/ |website=Via Satellite |language=en |date=2021-01-25}}</ref><ref>{{cite web|last=Grush|first=Loren|date=2020-09-03|title=With latest Starlink launch, SpaceX touts 100 Mbps download speeds and 'space lasers' |url=https://www.theverge.com/2020/9/3/21419841/spacex-starlink-internet-satellite-constellation-download-speeds-space-lasers|access-date=2020-09-03|publisher=The Verge}}</ref>
|-
| [[European Data Relay System]] (EDRS){{efn|EDRS is a [[Public–private partnership]] between [[Airbus]] and the [[European Space Agency]].}}
| Data relay to GEO satellites from LEO [[Earth observation satellite]]s and for [[intelligence, surveillance and reconnaissance]] missions
| [[Geostationary Earth Orbit|GEO]], [[Low Earth orbit|LEO]]
| Space-to-space
| 1.8 Gbit/s
| 7/9
| [[Tesat-Spacecom]]<ref>{{cite web|url=http://aviationweek.com/SpaceLaserRelay|archive-url=https://web.archive.org/web/20150315002635/http://aviationweek.com/SpaceLaserRelay|archive-date=2015-03-15|title=Inside The World's First Space-Based Commercial Laser-Relay Service|publisher=Aviation Week|access-date=2018-02-24}}</ref>
| Active since 2016<ref>{{cite web |title=European Data Relay Satellite System (EDRS) Overview |url=https://artes.esa.int/european-data-relay-satellite-system-edrs-overview |website=artes.esa.int |access-date=16 December 2022 |language=en}}</ref>
|-
|[[DARPA]] Blackjack
|Risk reduction efforts to test the viability of new military space capabilities provided by emerging commercial LEO constellations<ref name="sattoday-mil-leo" />
|LEO
|Space-to-space
|
|2/unknown<ref>{{cite web |last1=Hitchens |first1=Theresa |title=DARPA's Mandrake 2 satellites: communicating at the speed of light |url=https://breakingdefense.com/2022/08/darpas-mandrake-2-satellites-communicating-at-the-speed-of-light/ |website=Breaking Defense |date=25 August 2022}}</ref>
|[[Mynaric]],<ref>{{cite web |title=To boost its military space business, Lockheed Martin turns to commercial players |url=https://spacenews.com/to-boost-its-military-space-business-lockheed-martin-turns-to-commercial-players/ |website=SpaceNews |date=2020-11-23}}</ref> SA Photonics<ref>{{cite web |title=DoD to test laser communications terminals in low Earth orbit |url=https://spacenews.com/dod-to-test-laser-communications-terminals-in-low-earth-orbit/ |website=SpaceNews |date=2020-06-08}}</ref>
|Active since 2022<ref>{{cite web |last1=Erwin |first1=Sandra |title=Military experiment demonstrates intersatellite laser communications in low Earth orbit |url=https://spacenews.com/military-experiment-demonstrates-intersatellite-laser-communications-in-low-earth-orbit/ |website=SpaceNews |access-date=16 December 2022 |date=17 May 2022}}</ref>
|- style="background: #f0f0d0"
|[[Kuiper Systems|Amazon Kuiper]]
|[[Satellite constellation|Satellite mega-constellation]] for global telecommunications
|LEO
|Space-to-space<ref>{{cite web |last1=Erwin |first1=Sandra |title=Amazon to link Kuiper satellites to DoD's mesh network in space |url=https://spacenews.com/amazon-to-link-kuiper-satellites-to-dods-mesh-network-in-space/ |website=SpaceNews |access-date=16 December 2022 |date=14 October 2022}}</ref>
|
|0/>10,000
|
|Development
|- style="background: #f0f0d0"
|[[Space Development Agency|SDA]] Proliferated Warfighter Space Architecture
|Proliferated LEO constellation consisting of multiple layers serving needs of the [[U.S. Department of Defense]] (DoD).<ref name="sattoday-mil-leo">{{cite web|title=US Military Places a Bet on LEO for Space Security|url=http://interactive.satellitetoday.com/via/june-2021/us-military-places-a-bet-on-leo-for-space-security/|website=interactive.satellitetoday.com}}</ref>
|LEO
|Space-to-space
|2.5 Gbit/s<ref>{{cite web |last1=Space Development Agency |first1=Office of the Under Secretary of Defense For Research and Engineering (OUSD(R&E)) |title=Optical Communications Terminal (OCT) Standard Version 3.0 |url=https://www.sda.mil/wp-content/uploads/2022/04/SDA-OCT-Standard-v3.0.pdf |access-date=16 December 2022}}</ref>
|0/>1,000
|[[Mynaric]], SA Photonics (a [[CACI]] subsidiary), Skyloom, [[Tesat-Spacecom]]<ref>{{cite web |last1=Werner |first1=Debra |title=SDA slide reveals Tranche 0 optical terminal manufacturers |url=https://spacenews.com/sda-slide-reveals-tranche-0-optical-terminal-manufacturers/ |website=SpaceNews |access-date=16 December 2022 |date=18 October 2022}}</ref>
| Development
|- style="background: #f0f0d0"
|[[OneWeb]] Gen Two<ref>{{cite web |title=OneWeb 'plans optical links' for next generation of satellit |url=https://www.capacitymedia.com/articles/3827854/oneweb-plans-optical-links-for-next-generation-of-satellites |website=www.capacitymedia.com |date=March 2021 |language=en}}</ref>
|[[Satellite constellation|Satellite mega-constellation]] for global telecommunications
|LEO
|Space-to-space
|
|0/>1,000
|
|Development
|- style="background: #f0f0d0"
|[[Telesat]] LEO constellation
|[[Satellite constellation|Satellite mega-constellation]] for global telecommunications
|LEO
|Space-to-space
|
|0/752<ref>{{cite web |title=Telesat Lightspeed LEO Network {{!}} Telesat |url=https://www.telesat.com/leo-satellites/ |website=www.telesat.com |date=20 May 2020}}</ref>
|
|Development
|- style="background: #f0f0d0"
|Laser Light Communications
|[[Satellite constellation]] for global telecommunications building an optical [[backbone network]] in space
|MEO
|Space-to-space, Space-to-ground
|100 Gbit/s<ref>{{cite web|url=https://www.laserlightcomms.com/|title=HALO Global Network by Laser Light Communications|access-date=2018-11-13}}</ref>
|
|[[Ball Aerospace & Technologies]]<ref>{{cite news|url=https://www.nasdaq.com/article/ball-corp-prime-contractor-for-laser-lights-satellite-fleet-analyst-blog-cm389976|title=Ball Corp Prime Contractor for Laser Light's Satellite Fleet - Analyst Blog|date=2014-09-11|website=nasdaq.com|access-date=2018-02-24}}</ref>
|Development
|- style="background: #f0f0d0"
|[[Warpspace|WarpHub InterSat]]
|[[Inter-satellite service|Inter satellite]] data relay for LEO Earth observation satellites, space-to-ground communication uses RF.
|MEO
|Space-to-space
|1 Gbit/s<ref>{{cite web|url=https://warpspace.jp/pdf/WSPitch_201031.pdf#page=7|title=WarpHub InterSat|access-date=2021-03-03}}</ref>
|
|
|Development
|- style="background: #f0f0d0"
|Analytical Space<ref>{{cite web|url=http://www.wbur.org/bostonomix/2017/09/19/with-200-million-mits-the-engine-makes-its-first-investments-in-tough-tech|title=With US$200 Million, MIT's The Engine Makes Its First Investments In 'Tough Tech'|date=September 19, 2017|first=Asma|last=Khalid|website=wbur.org|access-date=2018-02-24}}</ref>
|In-space hybrid RF/optical data relay network for [[Earth observation satellite]]s
|[[Low Earth orbit|LEO]]
|Space-to-ground
|
|
|
|Development
|- style="background: #f0f0d0"
|BridgeComm<ref>{{cite web|url=https://www.bizjournals.com/boston/blog/techflash/2015/03/this-bostonstartup-is-building-a-faster-way-to.html|title=This Boston startup is building a faster way to send data from satellites — using lasers|last=Harris|first= David L.|date=March 12, 2015|publisher=Boston Business Journal|access-date=February 24, 2018}}</ref>
|Direct data downstream from LEO [[Earth observation satellite]]s to the ground
|LEO
|Space-to-ground
|1 Gbit/s
|
|[[Surrey Satellite Technology]]<ref>{{cite web|url=http://optics.org/news/7/4/20|title=Miniature satellites to transmit optical data from space|author=SPIE Europe|website=optics.org|access-date=2018-02-24}}</ref>
|Development
|- style="background: #f0f0d0"
|Cloud Constellation
|Secure data storage on satellites and secure intercontinental connections
|LEO
|Space-to-space
|
|
|[[Mynaric]]<ref>{{cite web |title=Cloud Constellation Selects Mynaric Laser OISL Terminals for its SpaceBelt Satellites - Via Satellite - |url=https://www.satellitetoday.com/manufacture/2021/05/20/cloud-constellation-selects-mynaric-laser-oisl-terminals-for-its-spacebelt-satellites/ |website=Via Satellite |language=en |date=2021-05-20}}</ref>
|Development
|- style="background: #e0e0e0"
|[[Facebook Aquila]]<ref>{{cite news|url=https://www.theverge.com/a/mark-zuckerberg-future-of-facebook/aquila-drone-internet|title=Inside the test flight of Facebook's first internet drone|last=Newton |first=Casey|date=2016-07-21|publisher=The Verge|access-date=2018-02-24}}</ref>
|Telecommunications for rural and remote areas provided by a network of [[High-altitude platform station|high-altitude platforms]]
|Stratosphere
|Air-to-air, Air-to-ground
|10 Gbit/s
|
|[[Mynaric]]<ref name="BI-Facebook"/>
|Terminated
|- style="background: #e0e0e0"
|[[LeoSat]]
|[[Satellite constellation|Satellite mega-constellation]] for global telecommunications
|LEO
|Space-to-space
|
|
|[[Thales Alenia Space]]<ref>{{cite web|url=http://optics.org/news/7/9/16|title=Thales signs deal on optically connected satellites|author=SPIE Europe|website=optics.org|access-date=2018-02-24}}</ref>
|Terminated<ref>{{cite web|title=LeoSat, absent investors, shuts down|url=https://spacenews.com/leosat-absent-investors-shuts-down/|publisher=SpaceNews|date=13 November 2019}}</ref>
|- style="background: #e0e0e0"
|[[Loon LLC|Google Loon]]<ref name=":02"/>
|Telecommunications for rural and remote areas provided by a network of [[High-altitude balloon|stratospheric balloons]]
|[[Stratosphere]]
|Air-to-air
|0.155 Gbit/s
|
|
|Terminated
|- style="background: #e0e0e0"
|SpaceLink
|Data relay services from MEO for LEO satellites
|[[Medium Earth orbit|MEO]], LEO
|Space-to-space
|
|
|[[Mynaric]]<ref>{{cite web |title=Mynaric, SpaceLink Partner to Accelerate Satellite Laser Terminal Technology - Via Satellite - |url=https://www.satellitetoday.com/innovation/2021/05/12/mynaric-spacelink-partner-to-accelerate-satellite-laser-terminal-technology/ |website=Via Satellite |access-date=2 June 2021 |language=en |date=2021-05-12}}</ref>
|Terminated<ref>{{cite web |last1=Werner |first1=Debra |title=SpaceLink to wind down operations, barring last-minute investment |url=https://spacenews.com/spacelink-wind-down/ |website=SpaceNews |access-date=16 December 2022 |date=31 October 2022}}</ref>
|}
{{smalldiv|1=
;Legend:{{legend|#f9f9f9|Active}}{{legend|#f0f0d0|Under development}}{{legend|#e0e0e0|Terminated}}
}}
{{notelist}}

=== Suppliers ===
A substantial market for laser communication equipment may establish when these projects will be fully realized.<ref>{{cite web|url=http://aviationweek.com/space/big-gains-horizon-laser-communications-suppliers |title=Big Gains On Horizon For Laser Communications Suppliers|publisher=Aviation Week|date=March 11, 2015|access-date=2018-02-24}}{{subscription required}}</ref> New advancements by equipment suppliers is enabling laser communications while reducing the cost. Beam modulation is being refined, as its software, and gimbals. Cooling problems have been addressed and photon detection technology is improving.{{citation needed|date=March 2018}} Currently active notable companies in the market include:
{| class="wikitable"
|+
!Company
!Product status
|-
|[[Ball Aerospace & Technologies|Ball Aerospace]] and [[Honeywell]]<ref>{{cite web|last1=Russell|first1=Kendall|title=Honeywell, Ball to Develop Optical Communication Links - Via Satellite -|url=https://www.satellitetoday.com/telecom/2018/04/17/honeywell-ball-to-develop-optical-communication-links/|publisher=Satellite Today|access-date=21 April 2018|date=17 April 2018}}</ref> [http://www.ball.com/aerospace/markets-capabilities/capabilities/electronic-warfare/laser-technologies <nowiki>[1]</nowiki>]
| in development
|-
|[[Ecuadorian Space Agency]]<ref>{{cite web|title=RBC Signals and Ecuadorian Civilian Space Agency (EXA) Announce Collaboration For Optical Communication System -|url=https://rbcsignals.com/rbc-signals-and-ecuadorian-civilian-space-agency-exa-announce-collaboration-for-optical-communication-system/|publisher=RBC Signals|access-date=28 February 2021|date=4 October 2018}}</ref><ref>{{cite web|title=LASER COMMUNICATIONS FOR CUBESATS: A 50 MBPS LASER/RADIO HYBRID TRANSCEIVER IN A PC-104 FORM FACTOR CARD -|url=https://www.researchgate.net/publication/336899550|publisher=Research Gate|access-date=28 February 2021|date=14 October 2019}}</ref>[https://www.cubesat.market/all-in-one<nowiki>[2]</nowiki>]
| TRL9 - in production
|-
|[[Hensoldt]] [https://www.hensoldt.net/solutions/air/optronics/laser-communication-terminal/<nowiki>[3]</nowiki>]
|
|-

|[[LGS Innovations]]<ref>{{cite news|url=http://www.satellitetoday.com/government-military/2016/05/18/darpa-awards-optical-satellite-terminal-contract-to-lgs-innovations/|title=DARPA Awards Optical Satellite Terminal Contract to LGS Innovations|first=Caleb|last=Henry|date=2016-05-18|publisher=Satellite Today|access-date=2018-02-24}}
</ref>
| 
|-
|Mostcom JSC [http://www.moctkom.ru/space-terminals/ <nowiki>[4]</nowiki>]
|in development
|-
|[[Mynaric]] [https://mynaric.com/<nowiki>[5]</nowiki>]
|
|-
|[[Sony]]<ref>{{cite web|title=Sony to launch space business|url=https://asia.nikkei.com/Business/Companies/Sony-to-launch-space-business|publisher=Nikkei Asian Review|date=April 15, 2018|access-date=21 April 2018}}</ref>
|in development
|-
|[[Surrey Satellite Technology]]
|in development
|-
|[https://www.skyloom.co/ Skyloom]
|in development
|-
|[[Tesat-Spacecom]] [http://tesat.de/en/products/laser-products<nowiki>%5B6%5D</nowiki>]
|TR9 operational since 2012
|-
|[[Thales Alenia Space]]
|
|-
|Transcelestial<ref>{{cite news|url=http://www.straitstimes.com/business/space-buffs-make-light-work-of-data-transfer|title=Space buffs make light work of data transfer|date=2017-03-22|publisher=The Straits Times|first=Rupali|last=Karekar|access-date=2018-02-24}}</ref> [http://www.transcelestial.com/ <nowiki>[7]</nowiki>]
|in development
|}

== Secure communications ==
Secure communications have been proposed using a laser [[N-slit interferometer]] where the laser signal takes the form of an interferometric pattern, and any attempt to intercept the signal causes the collapse of the interferometric pattern.<ref name=OC205>{{cite journal|author=F. J. Duarte|title=Secure interferometric communications in free space|journal=Optics Communications|volume=205|number=4|pages=313–319 |date=May 2002|doi=10.1016/S0030-4018(02)01384-6|bibcode=2002OptCo.205..313D|author-link=F. J. Duarte}}</ref><ref>{{cite journal|title=Secure interferometric communications in free space: enhanced sensitivity for propagation in the metre range|journal=Journal of Optics A: Pure and Applied Optics|volume=7|pages=73–75|number=1|date=January 2005|doi=10.1088/1464-4258/7/1/011|bibcode=2005JOptA...7...73D|author-link=F. J. Duarte|last1=Duarte |first1=F. J. }}</ref> This technique uses populations of indistinguishable photons<ref name=OC205/> and has been demonstrated to work over propagation distances of practical interest<ref>[http://iopscience.iop.org/2040-8986/13/3/035710 F. J. Duarte, T. S. Taylor, A. M. Black, W. E. Davenport, and P. G. Varmette, N-slit interferometer for secure free-space optical communications: 527 m intra interferometric path length, ''J. Opt'' '''13''', 035710 (2011)]</ref> and, in principle, it could be applied over large distances in space.<ref name=OC205/>

Assuming available laser technology, and considering the divergence of the interferometric signals, the range for satellite-to-satellite communications has been estimated to be approximately {{cvt|2000|km}}.<ref name=DT>[http://www.laserfocusworld.com/articles/print/volume-51/issue-04/features/interferometry-quantum-entanglement-physics-secures-space-to-space-interferometric-communications.html F. J. Duarte and T. S. Taylor, Quantum entanglement physics secures space-to-space interferometric communications, ''Laser Focus World'' '''51'''(4), 54-58 (2015)]</ref> These estimates are applicable to an array of satellites orbiting the Earth. For space vehicles or space stations, the range of communications is estimated to increase up to {{cvt|10000|km}}.<ref name=DT/> This approach to secure space-to-space communications was selected by [[Laser Focus World]] as one of the top [[photonics]] developments of 2015.<ref name=JW>J. Wallace, Technology Review: Top 20 technology picks for 2015 showcase wide scope of photonics advances, ''Laser Focus World'' '''51'''(12), 20-30 (2015)</ref>

== See also ==
{{Portal|Spaceflight}}

{{div col}}
* {{annotated link|European Data Relay System}}
* {{annotated link|Lunar Laser Communication Demonstration}}, tested in Oct/Nov 2013
* {{annotated link|Laser Communications Relay Demonstration}}
* [[Satellite constellation]]
** [[Starlink#v1.5 (operational)]]
* {{annotated link|Mars Telecommunications Orbiter|Mars Laser Communication Demonstration}}
* {{annotated link|Optical PAyload for Lasercomm Science}} (OPALS)
* {{annotated link|Deep Space Optical Communications}}
{{div col end}}
* [[TBIRD]], TeraByte InfraRed Delivery - tested in 2022.

== References ==
{{Reflist}}

== Further reading ==
* David G. Aviv (2006): Laser Space Communications, ARTECH HOUSE {{ISBN|1-59693-028-4}}

{{Optical communication}}

[[Category:Laser communication in space| ]]