Editing Halley's Comet (section)

===1986===
{{multiple image
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|image1=Comethalley-21mar1986.jpg
|caption1=Halley's Comet as seen on 21 March 1986
|image2=Animation of 1P／Halley orbit - 1986 apparition.gif
|caption2=Animation of 1P/Halley orbit - 1986 apparition<br>{{legend2|magenta|1P/Halley}}{{·}}{{legend2|Royalblue|Earth}}{{·}}{{legend2|Yellow|Sun}}
|image3=Halley path 1986.png
|caption3=Daily motion across sky during the 1986 passage of Halley's Comet
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The 1986 apparition of Halley's Comet was the least favourable on record. In February 1986, the comet and the Earth were on opposite sides of the Sun, creating the worst possible viewing circumstances for Earth observers during the previous 2,000 years.<ref name="Broughton1979"/> Halley's closest approach was 0.42 au.<ref name="JPL_summary"/> Additionally, increased [[light pollution]] from urbanisation caused many people to fail in attempts to see the comet. With the help of binoculars, observation from areas outside cities was more successful.<ref name="Australian_Astronomy"/> Further, the comet appeared brightest when it was almost invisible from the northern hemisphere in March and April 1986,<ref name="Ocala"/> with best opportunities occurring when the comet could be sighted close to the horizon at dawn and dusk, if not obscured by clouds.

The approach of the comet was first detected by astronomers [[David C. Jewitt]] and G. Edward Danielson on 16 October 1982 using the 5.1&nbsp;m [[Hale Telescope]] at [[Mount Palomar Observatory|Mount Palomar]] and a [[CCD camera]].<ref name="Recovery_ESA"/>

The first visual observation of the comet on its 1986 return was by an amateur astronomer, Stephen James O'Meara, on 24 January 1985. O'Meara used a home-built {{convert|24|in|mm|order=flip|adj=on}} telescope on top of [[Mauna Kea]] to detect the [[apparent magnitude|magnitude]] 19.6 comet.<ref name="Jan24"/> The first to observe Halley's Comet with the naked eye during its 1986 apparition were Stephen Edberg (then serving as the coordinator for amateur observations at the [[NASA]] [[JPL|Jet Propulsion Laboratory]]) and Charles Morris on 8 November 1985.<ref name="Naked_eye_NYT"/>

The 1986 apparition gave scientists the opportunity to study the comet closely, and several probes were launched to do so. The Soviet ''Vega 1'' probe began returning images of Halley on 4 March 1986, captured the first-ever image of its [[Comet nucleus|nucleus]],<ref name="situ"/> and made its flyby on 6 March. It was followed by the ''[[Vega 2]]'' probe, making its flyby on 9 March. On 14 March, the ''Giotto'' space probe, launched by the [[European Space Agency]], made the closest pass of the comet's nucleus.<ref name="situ"/> There also were two Japanese probes, [[Suisei (spacecraft)|''Suisei'']] and ''[[Sakigake]]''. Unofficially, the numerous probes became known as the [[Halley Armada]].<ref name="Suisei2008"/>

Based on data retrieved by the largest [[ultraviolet]] space telescope of the time, [[Astron (spacecraft)|''Astron'']], in December 1985, a group of Soviet scientists developed a model of the comet's [[Coma (cometary)|coma]].<ref name="Boyarchuk1986"/> The comet also was observed from space by the ''[[International Cometary Explorer]]'' (ICE). Originally launched as the ''International Sun-Earth Explorer 3'', the spacecraft was renamed, and departed the Sun-Earth {{L1}} [[Lagrangian point]] in 1982 in order to intercept the comets [[21P/Giacobini-Zinner]] and Halley.<ref name="Murdin2000"/> ICE flew through the tail of Halley's Comet, coming within about {{convert|40.2|e6km|e6mi|abbr=unit}} of the nucleus on 28 March 1986.<ref name="ISEE-3"/>{{sfn|Siddiqi|2018|pp=149–150}}

Two U.S. [[Space Shuttle]] missions—[[STS-51-L]] and [[STS-61-E]]—had been scheduled to observe Halley's Comet from [[low Earth orbit]]. The STS-51-L mission carried the ''Shuttle-Pointed Tool for Astronomy'' ([[Spartan Halley]]) satellite, also called the ''Halley's Comet Experiment Deployable'' (HCED).<ref name="Spartan-203"/> The mission to capture the ultraviolet [[Astronomical spectroscopy|spectrum]] of the comet [[Space Shuttle Challenger disaster|ended in disaster]] when the Space Shuttle ''Challenger'' disintegrated in flight, killing all seven astronauts onboard.<ref name="STS-51L"/> Scheduled for March 1986, STS-61-E was a ''Columbia'' mission carrying the ASTRO-1 platform to study the comet,{{sfn|Shayler|Burgess|2007|pp=431–476}} but the mission was cancelled following the ''Challenger'' disaster and ASTRO-1 would not fly until late 1990 on [[STS-35]].<ref name="STS-35"/>

In Japan, the comet was observed by Emperor [[Hirohito]], who was 84.<ref name="Upi1986"/> He had already seen it in 1910 when he was 8.<ref name="Upi1986"/>