Editing Giotto (spacecraft)

{{Short description|European mission to comets Halley and Grigg–Skjellerup (1985–1992)}}
{{Italic title}}
{{Use dmy dates|date=May 2020}}
{{More footnotes needed|date=April 2019}}
{{Infobox spaceflight
| name                  = ''Giotto''

<!--image of the spacecraft/mission-->
| image                 = Mission Giotto (timbre RFA).jpg
| image_caption         = Giotto spacecraft on a stamp
| image_size            = 

<!--Basic details-->
| mission_type          = [[Comet|Cometary]] flyby
| operator              = [[European Space Agency]]
| COSPAR_ID             = 1985-056A
| SATCAT                = 15875
| website               = [https://www.esa.int/Science_Exploration/Space_Science/Giotto_overview www.esa.int]
| mission_duration      = {{time interval|2 Jul 1985|23 Jul 1992|sep=,}}

<!--Spacecraft properties-->
| spacecraft_type       = [[GEOS (satellite)|GEOS]]
| manufacturer          = [[British Aerospace]]
| launch_mass           = 960 kg<ref name=beyond/>
| power                 = 196&nbsp;W

<!--Launch details-->
| launch_date           = {{start date|1985|07|02|11|23|00|7=Z|df=y}}
| launch_rocket         = [[Ariane 1]] V-14
| launch_site           = [[Guiana Space Centre|Kourou]] [[ELA-1]]
| launch_contractor     = [[Arianespace]]

<!--end of mission-->
| disposal_type         = Decommissioned
| deactivated           = {{end date|1992|07|23|df=y}}

<!--orbit parameters-->
| orbit_reference       = [[Heliocentric orbit|Heliocentric]]<ref name=nssdc1/>
| orbit_eccentricity    = 0.17334
| orbit_periapsis       = 0.73 [[Astronomical Unit|AU]]
| orbit_apoapsis        = 1.04 AU
| orbit_inclination     = 2.09°
| orbit_period          = 304.6 days
| orbit_epoch           = 10 July 1992, 15:18:43 UTC
| apsis                 = helion

|interplanetary         = <!--Infobox spaceflight/IP can be called multiple times for missions with multiple targets or combined orbiter/lander missions, etc-->
{{Infobox spaceflight/IP
   |type                = flyby
   |object              = [[Halley's Comet|1P/Halley]]
   |arrival_date        = 14 March 1986
   |distance            = {{convert|596|km|abbr=on}}
 }}

 {{Infobox spaceflight/IP
   |type                = flyby
   |object              = [[Earth]]
   |arrival_date        = 2 July 1990
   |distance            = {{convert|22730|km|abbr=on}}
 }}

 {{Infobox spaceflight/IP
   |type                = flyby
   |object              = [[26P/Grigg-Skjellerup]]
   |arrival_date        = 10 July 1992
   |distance            = {{convert|200|km|abbr=on}}
 }}

 {{Infobox spaceflight/IP
   |type                = flyby
   |object              = [[Earth]]
   |arrival_date        = 1999
   |distance            = ~{{convert|1000|km|abbr=on}}
}}

| programme             = '''[[Halley Armada]]'''
| previous_mission      = [[Sakigake]]
| next_mission          = [[Suisei (spacecraft)|Suisei]]

| insignia              = File:Giotto insignia.png
| insignia_caption      = Legacy ESA insignia for the ''Giotto'' mission
| insignia_alt          = Giotto legacy mission insignia
| insignia_size         = 180px
}}

'''''Giotto''''' was a [[Europe]]an [[robotic spacecraft]] mission from the [[European Space Agency]]. The spacecraft flew by and studied [[Halley's Comet]] and in doing so became the first spacecraft to make close up observations of a comet. On 13 March 1986, the spacecraft succeeded in approaching Halley's nucleus at a distance of 596 kilometers. It was named after the Early [[Italian Renaissance]] [[Painting|painter]] [[Giotto|Giotto di Bondone]]. He had observed Halley's Comet in 1301 and was inspired to depict it as the [[star of Bethlehem]] in his painting [[Scrovegni Chapel#The life of Christ|''Adoration of the Magi'' in the Scrovegni Chapel]].

==Mission==
===Development===
[[Image:Giotto Halley Grigg-Skjellerup orbit-multi-lang.svg|lang=en|thumb|left|''Giotto'' trajectory]]
Members of the ESA’s Solar System Working Group started investigating a mission to Halley’s comet in 1977 before rejecting it in August 1978 in favour of a lunar orbiter.<ref name=calder21 /> Shortly afterwards this was reversed by the Science Advisory Committee and the ESA started to study a joint mission with NASA.<ref name=calder21>{{cite book |last=Calder |first=Nigel |title=Giotto to the Comets |publisher=Presswork |publication-place=London |date=1992 |isbn=0-9520115-0-6 |pages=21-24}}</ref> This mission was to be the [[International Comet Mission]] consisting of a carrier NASA probe and smaller European probe based on the [[ISEE-2]].<ref name=calder25 /> The plan was for the American probe to release the European probe towards Halley for a close flyby before going on to explore Comet [[10P/Tempel]].<ref name=calder25>{{cite book |last=Calder |first=Nigel |title=Giotto to the Comets |publisher=Presswork |publication-place=London |date=1992 |isbn=0-9520115-0-6 |pages=25-28}}</ref> The NASA probe was cancelled November 1979.<ref name=Hughes>{{cite journal | last=Hughes | first=David W | title=The Giotto-Halley 20th anniversary | journal=Astronomy and Geophysics | volume=47 | issue=1 | date=2006 | issn=1366-8781 | doi=10.1111/j.1468-4004.2006.47127.x | pages=1.27–1.28}}</ref> 

Proposals then moved to an Ariane 1 launched mission with the first option considered being one suggested by [[Giuseppe Colombo]].<ref name=calder31 /> Named HAPPEN it involved using parts for a planned [[GEOS (satellite)|Geos-3]] satellite to first examine the earth's [[Magnetosphere#Magnetotail|Magnetotail]] before flying through the tail of Halley’s comet in march 1986.<ref name=calder31 />  This was rejected 24 January 1980 by the Solar System working group for not offering to return enough information on Halley.<ref name=calder31>{{cite book |last=Calder |first=Nigel |title=Giotto to the comets |publisher=Presswork |publication-place=London |date=1992 |isbn=0-9520115-0-6 |pages=31-32}}</ref> In February 1980 it was proposed that the Ariane 1 launch two Geos based probes.<ref name=calder33 /> One to examine the magnetotail and the other to target Halley’s comet.<ref name=calder33 /> It was at this point the name Giotto name started being used.<ref name=calder33>{{cite book |last=Calder |first=Nigel |title=Giotto to the comets |publisher=Presswork |publication-place=London |date=1992 |isbn=0-9520115-0-6 |pages=33-35}}</ref> The proposal was approved by the Science Advisory Committee and then moved onto the Science program committee.<ref name=calder33 /> The Science program committee initially rejected the mission in favour of the [[Hipparcos]] satellite while giving Giotto at chance for a second submission without the Magnetotail mission but with more extensive planning and a budget of 80 million accounting units.<ref name=calder35>{{cite book |last=Calder |first=Nigel |title=Giotto to the comets |publisher=Presswork |publication-place=London |date=1992 |isbn=0-9520115-0-6 |pages=35-36}}</ref> In July 1980 the committee approved the second proposal with a budget of 80 million accounting units.<ref name=calder38 /> The Hipparcos program, while delayed, also continued.<ref name=calder38>{{cite book |last=Calder |first=Nigel |title=Giotto to the comets |publisher=Presswork |publication-place=London |date=1992 |isbn=0-9520115-0-6 |page=38}}</ref>

During March 1981 British Aerospace submitted its Geos based design to the ESA.<ref name=calder54 /> This was rejected due to issues with power and temperature control.<ref name=calder54 /> In the same period it was found that the Geos design had become outdated to the point where it was no longer possible to obtain parts.<ref name=calder54 /> As a result a new and somewhat larger craft was designed although British Aerospace remained the primary contractor.<ref name=calder54>{{cite book |last=Calder |first=Nigel |title=Giotto to the comets |publisher=Presswork |publication-place=London |date=1992 |isbn=0-9520115-0-6 |pages=54-57}}</ref>

Originally it was planned to launch Giotto on an [[Ariane 2]] along with a commercial satellite.<ref name=calder65 /><ref name=calder33 /> This was then shifted to an [[Ariane 3]] before difficulties with finding a customer who wanted to fly during the launch window resulted in Giotto being assigned solo to an Ariane 1 which was available after [[EXOSAT]] was launched by a [[Thor-Delta]].<ref name=Dickson>{{cite journal |last=Dickson |first=David |title=Ariane Loses One to NASA |journal=Science |volume=219 |issue=4589 |date=11 March 1983 |issn=0036-8075 |doi=10.1126/science.219.4589.1202 |page=1202}}</ref><ref name=calder65>{{cite book |last=Calder |first=Nigel |title=Giotto to the Comets |publisher=Presswork |publication-place=London |date=1992 |isbn=0-9520115-0-6 |page=65}}</ref>

There were plans to have observation equipment on board a [[Space Shuttle]] in low-Earth orbit around the time of ''Giotto''{{'}}s fly-by, but they in turn fell through with the [[STS-51-L|''Challenger'' disaster]].

The plan then became a cooperative armada of five space probes including ''Giotto'', two from the [[Soviet Union]]'s [[Vega program]] and two from Japan: the ''[[Sakigake]]'' and [[Suisei (spacecraft)|''Suisei'']] probes. The idea was for Japanese probes and the pre-existing American probe [[International Cometary Explorer]] to make long distance measurements, followed by the Soviet Vegas which would locate the nucleus, and the resulting information sent back would allow ''Giotto'' to precisely target very close to the nucleus. Because ''Giotto'' would pass so very close to the nucleus ESA was mostly convinced it would not survive the encounter due to the spacecraft colliding at very high speed with the many dust particles from the comet. The coordinated group of probes became known as the [[Halley Armada]].

==Design==
{{Stack|[[File:Giotto Whipple shield ESA239195.jpg|thumb|upright|An image of the ''Giotto'' spacecraft during construction]]}}
The cylindrical spacecraft was 1.87&nbsp;m in diameter 2.85m long.<ref name=calder57>{{cite book |last=Calder |first=Nigel |title=Giotto to the Comets |publisher=Presswork |publication-place=London |date=1992 |isbn=0-9520115-0-6 |page=57}}</ref>  It had and had three internal platforms. Built by British Aerospace in Filton, Bristol, it carried a dust shield ([[Whipple shield]]) as proposed by [[Fred Whipple]]. The shield comprised a thin (1&nbsp;mm) [[aluminium]] sheet separated by a space and a thicker (12&nbsp;mm) [[Kevlar]] sheet.<ref name=":0">{{Cite web|title=Giotto Whipple shield|url=https://www.esa.int/ESA_Multimedia/Images/2009/02/Giotto_Whipple_shield|access-date=2022-01-21|website=www.esa.int|language=en}}</ref> The later [[Stardust (spacecraft)|''Stardust'' spacecraft]] would use a similar Whipple shield. Giotto also had a 1.51&nbsp;m diameter antenna that it used to communicate with [[Earth]].<ref name=":0"/> The craft was painted white using an electively conductive paint developed by [[Centre national d'études spatiales]].<ref name=calder76>{{cite book |last=Calder |first=Nigel |title=Giotto to the Comets |publisher=Presswork |publication-place=London |date=1992 |isbn=0-9520115-0-6 |page=76}}</ref>

A mock-up of the spacecraft resides at the Bristol Aero Collection hangar, at [[Filton]], [[Bristol]], [[England]].{{citation needed|date=December 2020}}

The craft was equipped with a Mage motor made by [[Societe Europeenne de Propulsion]].

=== Science Instruments ===
Giotto had 10 science instruments.<ref>{{Cite web|title=Giotto – PSA – Cosmos|url=https://www.cosmos.esa.int/web/psa/giotto|access-date=2022-01-19|website=www.cosmos.esa.int}}</ref><ref>{{Cite web|title=ESA Science & Technology – Instruments|url=https://sci.esa.int/web/giotto/-/31882-instruments|access-date=2022-01-19|website=sci.esa.int}}</ref>

* MAG: a magnetometer 
* HMC (Halley Multicolour Camera): a 16-cm telescope and camera
* DID (Dust Impactor Detector System): measured the mass of dust particles that hit the instrument
* RPA (Rème Plasma Analyser): studied solar wind and charged particles
* JPA (Johnstone Plasma Analyser): also measured solar wind and charged particles
* PIA (Particulate Impact Analyser): studied the size and chemistry of particles
* OPE (Optical Probe Experiment): examined the emissivity of gas and dust behind the spacecraft
* EPA (Energetic Particle Analyser): analyzed alpha-particles, electrons, and neutrons
* NMS (Neutral Mass Spectrometer): measured the composition of the particles around the comet
* IMS (Ion Mass Spectrometer): measured the amount of ions from the sun and the comet
* GRE (Giotto Radio Experiment): used Giotto's radio signals to study Halley's comet

==Timeline==

===Launch===
The mission was given the go-ahead by ESA in 1980, and launched
on an [[Ariane 1]] rocket (flight V14) on 2 July 1985 from [[Kourou, French Guiana]]. The craft was controlled from the European Space Agency [[European Space Operations Centre|ESOC facilities]] in [[Darmstadt]] (then West Germany) initially in [[Geostationary transfer orbit|Geostationary Transfer Orbit]] (GTO) then in the Near Earth Phase (NEP) before the longer Cruise Phase through to the encounter. While in GTO a number of slew and spin-up manoeuvres (to 90 [[revolutions per minute|RPM]]) were carried out in preparation for the firing of the [[Apogee kick motor|Apogee Boost Motor]] (ABM), although unlike orbit circularisations for [[geostationary orbit]], the ABM for Giotto was fired at [[Apsis|perigee]]. Attitude determination and control used sun pulse and IR [[Earth sensor]] data in the telemetry to determine the spacecraft orientation.

===Halley encounter===

The [[Soviet Union|Soviet]] [[Vega 1]] started returning images of Halley on 4 March 1986, and the first ever of its nucleus, and made its flyby on 6 March, followed by [[Vega 2]] making its flyby on 9 March. Vega 1's closest approach to Halley was
8&thinsp;889&nbsp;km.

''Giotto'' passed Halley successfully on 14 March 1986 at 596&nbsp;km distance, and surprisingly survived despite being hit by some small particles. One impact sent it spinning off its stabilized spin axis so that its antenna no longer always pointed at the Earth, and its dust shield no longer protected its instruments. After 32 minutes ''Giotto'' re-stabilized itself and continued gathering science data.

Another impact destroyed the Halley Multicolor Camera, but not before it took photographs of the nucleus at closest approach.

[[File:Comet Halley close up.jpg|thumb|Comet Halley at Giotto spacecraft's closest approach]]

===First Earth flyby===

''Giotto''{{'}}s trajectory was adjusted for an Earth flyby and its science instruments were turned off on 15 March 1986 at 02:00 UTC.

===Grigg–Skjellerup encounter===

''Giotto'' was commanded to wake up on 2 July 1990 when it flew by Earth in order to sling shot to its next cometary encounter.

The probe then flew by the [[26P/Grigg–Skjellerup|Comet Grigg–Skjellerup]] on 10 July 1992 which it approached to a distance of about 200&nbsp;km. Afterwards, Giotto was again switched off on 23 July 1992.

The cost of this mission extension was $6.3 million.<ref>{{cite journal |last1=Holden |first1=Constance |date=10 July 1992 |title=Random Samples  |url=http://www.jstor.org/stable/2877514  |journal=Science |volume=257 |issue=5067 |pages=160-161  |access-date=11 March 2025}}</ref>

===Second Earth flyby===

In 1999 ''Giotto'' made another Earth flyby but was not reactivated.<ref name=Portree />

==Scientific results==

Images showed Halley's nucleus to be a dark peanut-shaped body, 15&nbsp;km long, 7&nbsp;km to 10&nbsp;km wide. Only 10% of the surface was active, with at least three outgassing jets seen on the sunlit side. Analysis showed the comet formed 4.5 billion years ago from volatiles (mainly ice) that had condensed onto interstellar dust particles. It had remained practically unaltered since its formation.

Measured volume of material ejected by Halley:

* 80% [[water]],
* 10% [[carbon monoxide]]
* 2.5% a mix of [[methane]] and [[ammonia]].
* other [[hydrocarbon]]s, [[iron]], and [[sodium]] were detected in trace amounts.

''Giotto'' found Halley's nucleus was dark, which suggested a thick covering of dust.<ref name="esa">{{cite web|title=ESA Science & Technology: Halley |publisher=[[ESA]] |url=http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31878 |date=10 March 2006 |access-date=22 February 2009}}</ref>

The nucleus's surface was rough and of a porous quality, with the density of the whole nucleus as low as 0.3 g/cm<sup>3</sup>.<ref name="esa" /> Sagdeev's team estimated a density of
0.6 g/cm<sup>3</sup>,<ref name="density">{{Cite journal|title=Is the nucleus of Comet Halley a low density body?|volume= 331|issue= 6153|pages= 240|author= RZ Sagdeev|author2= PE Elyasberg|authorlink2=Pavel Elyasberg|author3= VI Moroz|journal=Nature|bibcode=1988Natur.331..240S|year=1988|doi= 10.1038/331240a0|s2cid= 4335780}}</ref> but S. J. Peale warned that all estimates had error bars too large to be informative.<ref name="Peale">{{cite journal |title=On the density of Halley's comet |author=S. J. Peale |journal=[[Icarus (journal)|Icarus]] |volume=82 |issue=1 |pages=36–49 |date = November 1989|doi=10.1016/0019-1035(89)90021-3 |bibcode=1989Icar...82...36P}}</ref>

The quantity of material ejected was found to be three tonnes per second<ref name="mcd">{{cite journal |title=Dust density and mass distribution near comet Halley from Giotto observations |author=J. A. M. McDonnell |display-authors=etal |journal=Nature |volume=321 |issue=6067s |pages=338–341 |date=15 May 1986 |doi=10.1038/321338a0 |bibcode = 1986Natur.321..338M |s2cid=122092751 }}</ref> for seven jets, and these caused the comet to wobble over long time periods.<ref name="esa" />

The dust ejected was mostly only the size of cigarette smoke particles, with [[Orders of magnitude (mass)|masses ranging from]] 10 ag to 0.4 g. (See [[Orders of magnitude (mass)]].) The mass of the particle that impacted ''Giotto'' and sent it spinning was not measured, but from its effects—it also probably broke off a piece of ''Giotto''<ref name="mcd" />—the mass has been estimated to lie between 0.1&nbsp;g and 1&nbsp;g.<ref name="esa" />

Two kinds of dust were seen: one with carbon, hydrogen, nitrogen and oxygen; the other with calcium, iron, magnesium, silicon and sodium.<ref name="esa" />

The ratio of abundances of the comet's light elements excluding nitrogen (i.e. hydrogen, carbon, oxygen) were the same as the Sun's. The implication is that the constituents of Halley are among the most primitive in the Solar System.

The plasma and ion mass spectrometer instruments showed Halley has a carbon-rich surface.

===Spacecraft achievements===

* ''Giotto'' made the closest approach to Halley's Comet and provided the best data for this comet.<ref name=Curdt_1988/>
* ''Giotto'' was the first spacecraft:
:* to provide detailed pictures of a cometary nucleus.<ref name=Keller_1986/>
:* to make a close flyby of two comets. Young and active comet [[Halley's Comet|Halley]] could be compared to old comet [[Grigg–Skjellerup]].
:* to return from interplanetary space and perform an Earth swing-by.
:* to be re-activated from hibernation mode.
:* to use Earth for a gravity assist.<ref name=beyond/>

==Giotto II Proposals==
A proposal was made to use spare parts to build a backup craft.<ref name=Walgate>{{cite news |last=Walgate |first=Robert |date=26 January 1984 |title=Europe's hopes for second probe  |url=https://www.nature.com/articles/307308a0.pdf |work=Nature |location= |publisher=Macmillan Journals Ltd |access-date=11 March 2024}}</ref> A second proposal was made to use a Giotto based probe to return a sample of a comet coma with a re-entry capsule in place of the Mage motor.<ref name=Portree>{{cite news |last=Portree |first=David.S.F |date=22 June 2012 |title=Capturing a Comet: Giotto II (1985) |url=https://www.wired.com/2012/06/capturing-a-comet-giotto-ii-1985/ |work=Wired |location= |publisher=Condé Nast  |access-date=11 March 2024}}</ref>

==See also==
* [[Timeline of Solar System exploration]]
* [[Rosetta (spacecraft)]]
* [[Philae (spacecraft)]]

==References==
{{Reflist|refs=

<ref name="beyond">{{ cite book
| url= https://www.nasa.gov/sites/default/files/atoms/files/beyond-earth-tagged.pdf
| title= Beyond Earth: A Chronicle of Deep Space Exploration, 1958–2016
| author1= Asif Siddiqi
| publisher= [[NASA]]
| edition= second
| year= 2018
| isbn= 978-1-626-83043-1
| access-date= 30 November 2022 }}
</ref>

<ref name="Curdt_1988">{{Cite journal
| author1= W. Curdt
| author2= K. Wilhelm
| author3= A. Craubner
| author4= E. Krahn
| author5= H. U. Keller
| bibcode= 1988A&A...191L...1C
| title= Position of comet 1P/Halley at the Giotto encounter
| issn= 0004-6361
| journal= Astronomy and Astrophysics
| volume= 191
| number= 1
| pages= L1–L3
| date= February 1988 }}
</ref>

<ref name="Keller_1986">{{Cite journal
| author1= H. U. Keller
| author2= C. Arpigny
| author3= C. Barbieri
| author4= R. M. Bonnet
| author5= S. Cazes
| author6= M. Coradini
| author7= C. B. Cosmovici
| author8= W. A. Delamere
| author9= W. F. Huebner
| author10= D. W. Hughes
| author11= C. Jamar
| author12= D. Malaise
| author13= H. J. Reitsema
| author14= H. U. Schmidt
| author15= W. K. H. Schmidt
| author16= P. Seige
| author17= F. L. Whipple
| author18= K. Wilhelm
| doi= 10.1038/321320a0
| title= First Halley Multicolour Camera imaging results from Giotto
| journal= [[Nature (journal)|Nature]]
| volume= 321
| issue= 6067
| pages= 320–326
| date= 15 May 1986
| bibcode= 1986Natur.321..320K
| s2cid= 120631677
| display-authors= 8 }}
</ref>

<ref name="nssdc1">{{cite web
| url= https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1985-056A
| title= Giotto
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]]
| access-date= 21 June 2016 }}
</ref>

}}

==External links==
{{Commons category|Giotto (spacecraft)}}
{{Portal|Spaceflight}}
* [https://web.archive.org/web/20110604045249/http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=14610&fareaid=15 Mission website]
* [https://web.archive.org/web/20110516142812/http://solarsystem.nasa.gov/news/display.cfm?News_ID=750 Interview with the mission's Deputy Project Scientist] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [http://www.nature.com/nature/journal/v321/n6067s/index.html ''Nature'' 1986 about ''Giotto'' mission]
* [http://commons.wikimedia.org/wiki/Image:Giotto_-_Scrovegni_-_-18-_-_Adoration_of_the_Magi.jpg Giotto di Bondone's ''Adoration of the Magi'' painting that includes his rendition of Halley's Comet]
* [https://web.archive.org/web/20110927022415/http://sse.jpl.nasa.gov/multimedia/display.cfm?IM_ID=11423 Image of Halley in 1986 by ''Giotto'' spacecraft]
* [https://pdssbn.astro.umd.edu/data_sb/missions/giotto/index.shtml ''Giotto Mission Archive''] at the NASA Planetary Data System, Small Bodies Node
* [https://pdssbn.astro.umd.edu/data_sb/missions/gem/index.shtml ''Giotto Extended Mission Archive''] at the NASA Planetary Data System, Small Bodies Node

{{Comet spacecraft}}
{{European Space Agency}}
{{Orbital launches in 1985}}
{{Authority control}}

[[Category:Giotto di Bondone]]
[[Category:European Space Agency space probes]]
[[Category:Missions to comets]]
[[Category:Satellites orbiting the Sun]]
[[Category:1985 in spaceflight]]
[[Category:Derelict space probes]]
[[Category:Missions to Halley's Comet]]
[[Category:Spacecraft launched in 1985]]