Editing Subaru Telescope (section)

== Overview ==

The Subaru Telescope is a [[Ritchey-Chretien]] reflecting telescope. Instruments can be mounted at a [[Cassegrain reflector|Cassegrain]] focus below the primary mirror; at either of two [[Nasmyth telescope|Nasmyth]] focal points in enclosures on the sides of the telescope mount, to which light can be directed with a tertiary mirror; or at the [[prime focus]] in lieu of a secondary mirror, an arrangement rare on large telescopes, to provide a wide [[field of view]] suited to deep wide-field surveys.<ref>{{cite web |url=http://www.subarutelescope.org/Introduction/telescope.html |title=Specifications |publisher=Subaru Telescope" |access-date=September 22, 2010 |archive-date=April 6, 2011 |archive-url=https://web.archive.org/web/20110406104642/http://www.subarutelescope.org/Introduction/telescope.html |url-status=live }}</ref>

In 1984, the [[University of Tokyo]] formed an engineering working group to develop and study the concept of a {{convert|7.5|m|in|adj=on}} telescope. In 1985, the astronomy committee of Japan's science council gave top priority to the development of a "Japan National Large Telescope" (JNLT), and in 1986, the University of Tokyo signed an agreement with the [[University of Hawaii]] to build the telescope in Hawaii. In 1988, the National Astronomical Observatory of Japan was formed through a reorganization of the University's Tokyo Astronomical Observatory, to oversee the JNLT and other large national astronomy projects.<ref name=performance>{{Citation |url=http://optik2.mtk.nao.ac.jp/~iye/papers/iye208.pdf |archive-url=https://web.archive.org/web/20110722073446/http://optik2.mtk.nao.ac.jp/~iye/papers/iye208.pdf |url-status=dead |archive-date=July 22, 2011 |title=Current Performance and On-Going Improvements of the 8.2m Subaru Telescope |arxiv=astro-ph/0405012 |journal=Publ. Astron. Soc. Jpn. |volume=56 |issue=2 |pages=381–397 |date=April 25, 2004 |bibcode=2004PASJ...56..381I |doi=10.1093/pasj/56.2.381 |last1=Iye |first1=M. |last2=Karoji |first2=H. |last3=Ando |first3=H. |last4=Kaifu |first4=N. |last5=Kodaira |first5=K. |last6=Aoki |first6=K. |last7=Aoki |first7=W. |last8=Chikada |first8=Y. |last9=Doi |first9=Y. |last10=Ebizuka |first10=N. |last11=Elms |first11=B. |last12=Fujihara |first12=G. |last13=Furusawa |first13=H. |last14=Fuse |first14=T. |last15=Gaessler |first15=W. |last16=Harasawa |first16=S. |last17=Hayano |first17=Y. |last18=Hayashi |first18=M. |last19=Hayashi |first19=S. |last20=Ichikawa |first20=S. |last21=Imanishi |first21=M. |last22=Ishida |first22=C. |last23=Kamata |first23=Y. |last24=Kanzawa |first24=T. |last25=Kashikawa |first25=N. |last26=Kawabata |first26=K. |last27=Kobayashi |first27=N. |last28=Komiyama |first28=Y. |last29=Kosugi |first29=G. |last30=Kurakami |first30=T. |display-authors=29 }}</ref>

Construction of the Subaru Telescope began in April 1991, and later that year, a public contest gave the telescope its official name, "Subaru Telescope". Construction was completed in 1998, and the first scientific images were taken in January 1999.<ref>{{cite web |url=http://www.naoj.org/NAOJ/history.html |title=A Brief History of Subaru |publisher=Naoj.org |access-date=September 22, 2010 |archive-date=November 17, 2016 |archive-url=https://web.archive.org/web/20161117231626/http://www.naoj.org/NAOJ/history.html |url-status=live }}</ref>  In September 1999, [[Princess Sayako]] of Japan dedicated the telescope.<ref>{{cite web |last=French |first=Howard W. |url=https://www.nytimes.com/1999/09/19/world/on-hawaii-a-telescope-widens-orbit-of-japanese.html |title=On Hawaii, A Telescope Widens Orbit Of Japanese |location=Japan; Hawaii; Mount Mauna Kea (Hawaii) |work=[[The New York Times]] |date=September 19, 1999 |access-date=September 22, 2010 |archive-date=June 18, 2013 |archive-url=https://web.archive.org/web/20130618034254/http://www.nytimes.com/1999/09/19/world/on-hawaii-a-telescope-widens-orbit-of-japanese.html |url-status=live }}</ref>

A number of state-of-the-art technologies were worked into the telescope design. For example, 261 computer-controlled actuators press the main mirror from underneath, which corrects for primary mirror distortion caused by changes in the telescope orientation. The telescope enclosure building is also shaped to improve the quality of astronomical images by minimizing the effects caused by atmospheric turbulence.

Subaru is one of the few state-of-the-art telescopes to have been used with the naked eye. For the dedication, an eyepiece was constructed so that Princess Sayako could look through it directly. It was enjoyed by the staff for a few nights until it was replaced with the much more sensitive working instruments.<ref>{{Citation |url=http://ngm.nationalgeographic.com/print/2009/07/telescopes/ferris-text |archive-url=https://web.archive.org/web/20090620091739/http://ngm.nationalgeographic.com/print/2009/07/telescopes/ferris-text |url-status=dead |archive-date=June 20, 2009 |title=Cosmic Vision |journal=National Geographic |date=July 2009 |first=Timothy |last=Ferris |access-date=September 13, 2009}}</ref>

Subaru is the primary tool in the search for [[Planet Nine]]. Its large field of view, 75 times that of the Keck telescopes, and strong light-gathering power are suited for deep wide-field sky surveys. The search, split between a research group led by [[Konstantin Batygin]] and [[Michael E. Brown|Michael Brown]] and another led by [[Scott Sheppard]] and [[Chad Trujillo]], is expected to take up to five years.<ref name="sciencemag201601">{{cite news|url=http://www.sciencemag.org/news/2016/01/feature-astronomers-say-neptune-sized-planet-lurks-unseen-solar-system|title=Astronomers say a Neptune-sized planet lurks beyond Pluto|last=Hand|first=Eric|date=January 20, 2016|work=Science|access-date=January 20, 2016|archive-date=February 5, 2016|archive-url=https://web.archive.org/web/20160205031819/http://www.sciencemag.org/news/2016/01/feature-astronomers-say-neptune-sized-planet-lurks-unseen-solar-system|url-status=live}}</ref>

=== Accidents during construction ===
Two separate incidents claimed the lives of four workers during the construction of the telescope. On October 13, 1993, 42-year-old Paul F. Lawrence was fatally injured when a forklift tipped over onto him. On January 16, 1996, sparks from a welder ignited insulation which smoldered, generating noxious smoke that killed Marvin Arruda, 52, Ricky Del Rosario, 38, and Warren K. "Kip" Kaleo, 36, and sent twenty-six other workers to the hospital in Hilo. All four workers are memorialized by a plaque outside the base of the telescope dome and a sign posted temporarily each January along the Mauna Kea access road.

===Mishap in 2011===
On July 2, 2011, the telescope operator in Hilo noted an anomaly from the top unit of the telescope.<ref>{{Cite news|url=https://www.universetoday.com/87245/subaru-8-meter-telescope-damaged-by-leaking-coolant/|title=SUBARU 8-METER TELESCOPE DAMAGED BY LEAKING COOLANT|last=Atkinson|first=Nancy|date=December 24, 2015|work=Universe Today|access-date=April 10, 2017|archive-date=April 11, 2017|archive-url=https://web.archive.org/web/20170411054946/https://www.universetoday.com/87245/subaru-8-meter-telescope-damaged-by-leaking-coolant/|url-status=live}}</ref> Upon further examination, coolant from the top unit was found to have leaked over the primary mirror and other parts of the telescope.<ref>{{cite web|url=http://subarutelescope.org/Announce/2011/07/04/report1.html |title=Serious Hardware Incident with the Subaru Telescope Interrupts Its Operation |publisher=web-subarutelescope.org/ |access-date=July 5, 2011}}</ref>
Observation using Nasmyth foci resumed on July 22, and Cassegrain focus resumed on August 26.<ref>{{cite web |url=http://subarutelescope.org/Announce/2011/07/04/report4.html |title=Report 4: Resumption of Open Use Observations at Cassegrain Focus |date=September 13, 2011 |author=National Astronomical Observatory of Japan |access-date=September 23, 2011 |archive-date=July 16, 2012 |archive-url=https://archive.today/20120716152724/http://subarutelescope.org/Announce/2011/07/04/report4.html |url-status=live }}</ref>

===Mishap in 2023===
On September 15, 2023, an abnormal load sensor value of the primary mirror fixed point was observed during a maintenance operational test. Later, a part fell onto the primary mirror during repair work of the mirror cover.  Science observation was suspended.<ref name="subarutelescope20231016">{{cite web |url=https://subarutelescope.org/en/news/announcements/2023/10/16/3312.html |title=Regarding the suspention of Subaru Telescope night observation (3rd report) |publisher=National Astronomical Observatory of Japan |date=16 October 2023 |access-date=14 November 2023 |archive-date=November 14, 2023 |archive-url=https://web.archive.org/web/20231114022027/https://subarutelescope.org/en/news/announcements/2023/10/16/3312.html |url-status=live }}</ref>

After the replacement of sensor and the repair work of the primary mirror damage, it returned to observation on 3 March 2024.<ref>{{cite web |url=https://subarutelescope.org/en/news/announcements/2024/03/04/3372.html |title=Regarding the suspension of Subaru Telescope night observation (7th report) |publisher=Subaru Telescope |date=5 March 2024 |access-date=7 March 2024 |archive-date=December 3, 2024 |archive-url=https://web.archive.org/web/20241203140625/https://subarutelescope.org/en/news/announcements/2024/03/04/3372.html |url-status=live }}</ref>