View source for Euclid (spacecraft)

{{Short description|European visible and near-infrared space observatory}}
{{Lead too long|date=October 2024}}
{{EngvarB|date=September 2013}}
{{Italic title|string=Euclid}}
{{Use dmy dates|date=July 2023}}

{{Infobox spaceflight
| name               = ''Euclid''
| names_list         = Dark Universe Explorer (DUNE)<br/>Spectroscopic All Sky Cosmic Explorer (SPACE)<ref name="overview">{{cite web|url=http://www.esa.int/Science_Exploration/Space_Science/Euclid_overview|title=Euclid overview|website=esa.int}}</ref>

<!--image of the spacecraft/mission-->| image              = Euclid looking into the Universe ESA24697255.jpeg
| image_caption      = Artist's impression
| image_alt          = Euclid rendering
| image_size         = <!--Basic details-->
| mission_type       = [[Space telescope|Astronomy]]
| operator           = [[ESA]]
| COSPAR_ID          = <!--spacecraft launched since 1963 only (aka NSSDC ID; eg. 1998-067A)-->
| SATCAT             = <!--satellite catalogue number, omit leading zeroes (e.g. 25544)-->
| website            = {{URL|1=https://sci.esa.int/web/euclid/|2=sci.esa.int/euclid}}<br/>{{URL|1=https://www.euclid-ec.org/|2=euclid-ec.org}}
| mission_duration   = 6 years (nominal) <br/> {{time interval|1 July 2023 15:12|show=ymd}} (in progress)<ref name="ecSpacecraft">{{cite web|url=http://www.euclid-ec.org/?page_id=2540|title=Mission Characteristic – Euclid Consortium|date=28 December 2015|publisher=Euclid Consortium|access-date=26 April 2016|archive-date=16 March 2022|archive-url=https://web.archive.org/web/20220316132442/https://www.euclid-ec.org/?page_id=2540|url-status=dead}}</ref>

<!--Spacecraft properties-->| manufacturer       = [[Thales Alenia Space]] (main)<br/>[[Airbus Defence and Space]] (payload module)<ref name="new-fact-sheet">{{cite web |title=FACT SHEET |url=https://sci.esa.int/web/euclid/-/fact-sheet |website=euclid |publisher=[[ESA]] |date=24 January 2023 |access-date=7 July 2023}}</ref>
| launch_mass        = {{convert|2000|kg|abbr=on}}<ref name="new-fact-sheet"/>
| dry_mass           = <!--spacecraft mass in orbit without fuel-->
| payload_mass       = {{convert|800|kg|abbr=on}}<ref name="new-fact-sheet"/>
| dimensions         = {{convert|4.5|x|3.1|m|ft|abbr=on}}<ref name="new-fact-sheet"/>
| power              = <!--end-of-life power, in watts-->
| launch_date        = 1 July 2023 15:12 UTC<ref name="nxsf-euclid">{{cite web |url=https://nextspaceflight.com/launches/details/2008 |title=Falcon 9 Block 5 – Euclid Telescope |date=5 June 2023 |access-date=5 June 2023 |work=Next Spaceflight}}</ref>
| launch_rocket      = [[Falcon 9]]
| launch_site        = [[Cape Canaveral]] [[Cape Canaveral Space Launch Complex 40|SLC-40]]
| launch_contractor  = [[SpaceX]]
| orbit_reference    = [[Lagrangian point#L2|Sun–Earth L<sub>2</sub>]]<ref name="new-fact-sheet"/>
| orbit_regime       = [[Lissajous orbit]]
| orbit_semimajor    = <!--semimajor axis-->
| orbit_eccentricity = <!--orbital eccentricity-->
| orbit_periapsis    = {{convert|1150000|km|mi|abbr=on}}
| orbit_apoapsis     = {{convert|1780000|km|mi|abbr=on}}
| orbit_period       = <!--time taken to complete an orbit-->
| orbit_epoch        = Planned
| orbit_rev_number   = <!--revolution number-->
| apsis              = apsis

<!--Telescope parameters-->| telescope_type     = [[Korsch telescope]]
| telescope_diameter = {{convert|1.2|m|abbr=on}}<ref name="esaTelescope">{{cite web|url=http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=46676&fbodylongid=2158|title=Euclid Spacecraft – Telescope|date=24 January 2013|publisher=[[European Space Agency|ESA]]|access-date=13 April 2011}}</ref>
| telescope_focal_length = {{convert|24.5|m|abbr=on}}<ref name="esaTelescope"/>
| telescope_area     = {{convert|1.006|m2|sqft|abbr=on}}<ref name="eoPortal">{{cite web|url=https://directory.eoportal.org/web/eoportal/satellite-missions/content/-/article/euclid|title=Euclid – Mapping the geometry of the dark Universe|publisher=[[ESA]] Earth Observation Portal|access-date=5 January 2022|archive-date=5 January 2022|archive-url=https://web.archive.org/web/20220105160928/https://directory.eoportal.org/web/eoportal/satellite-missions/content/-/article/euclid|url-status=dead}}</ref>
| telescope_wavelength = From 550&nbsp;[[Nanometre|nm]] (green)<ref name="euclid-VIS" /><br/>to 2&nbsp;[[Micrometre|μm]] (near-[[Infrared astronomy|infrared]])<ref name="euclid-NISP" />
| telescope_resolution = 0.1 [[Arcsecond|arcsec]] ([[Visible-light astronomy|visible]])<br />0.3 [[Arcsecond|arcsec]] (near-[[Infrared astronomy|infrared]])<ref name="eoPortal"/>

<!--transponder parameters-->| trans_band         = [[X band]] (TT&C support)<br/>[[K band (NATO)|K band]] (data acquisition)
| trans_frequency    = 8.0–8.4&nbsp;GHz (X band)<br/>25.5–27&nbsp;GHz (K band)
| trans_bandwidth    = Few kbit/s down & up (X band)<br/>74&nbsp;Mbit/s (K band)<ref>{{cite web | url=https://www.esa.int/Science_Exploration/Space_Science/Euclid/Follow_Euclid_s_first_months_in_space | title=Follow Euclid's first months in space }}</ref>
| instruments_list   = {{Infobox spaceflight/Instruments
  | acronym1  = VIS  | name1 = VISible imager<ref name="euclid-VIS" />
  | acronym2  = NISP | name2 = Near Infrared Spectrometer and Photometer<ref name="euclid-NISP" />
 }}

<!--mission insignia or patch-->| insignia           = Euclid launch kit cover insignia.png
| insignia_caption   = The ESA astrophysics insignia for Euclid mission
| insignia_alt       = Euclid mission logo
| insignia_size      = 150px
| programme          = '''[[European Space Agency Science Programme#Cosmic Vision|Cosmic Vision]]'''
| previous_mission   = [[Solar Orbiter]]
| next_mission       = [[Jupiter Icy Moons Explorer|JUICE]]
}}

'''''Euclid''''' is a wide-angle [[space telescope]] with a 600-megapixel camera to record [[Visible spectrum|visible light]], a [[near-infrared]] [[spectrometer]], and [[photometer]], to determine the [[redshift]] of detected [[galaxies]]. It was developed by the [[European Space Agency]] (ESA) and the Euclid Consortium and was launched on 1 July 2023 from [[Cape Canaveral]] in Florida.<ref name="NYT-20230701">{{cite news |last=Miller |first=Katrina |title=The Dark Universe Is Waiting. What Will the Euclid Telescope Reveal? – The European Space Agency mission, which launched on Saturday, will capture billions of galaxies to create a cosmic map spanning space and time. |url=https://www.nytimes.com/2023/07/01/science/spacex-euclid-launch.html |date=1 July 2023 |work=[[The New York Times]] |url-status=live |archive-url=https://archive.today/20230701145541/https://www.nytimes.com/2023/07/01/science/spacex-euclid-launch.html |archive-date=1 July 2023 |access-date=2 July 2023 }}</ref><ref name="launch">{{cite web |url=https://interestingengineering.com/science/euclid-successfully-launched-into-space-by-falcon-9-rocket|title=Euclid successfully launched into space by Falcon 9 rocket|publisher=Interesting Engineering|date=1 July 2023|access-date=1 July 2023}}</ref>

After approximately one month, it reached its destination, a [[halo orbit]] around the Sun-Earth second [[Lagrange point]] L2, at an average distance of 1.5 million kilometres beyond [[Earth's orbit]] (or about four times the distance from the Earth to the Moon). There the telescope is expected to remain operational for at least six years. It joins the ''[[Gaia (spacecraft)|Gaia]]'' and [[James Webb Space Telescope]] missions at L2.

The objective of the ''Euclid'' mission is to better understand [[dark energy]] and [[dark matter]] by accurately measuring the [[accelerating expansion of the universe]]. To achieve this, the [[Korsch telescope|Korsch]]-type telescope will measure the shapes of galaxies at varying distances from Earth and investigate the relationship between distance and [[redshift]]. [[Dark energy]] is generally accepted as contributing to the increased [[Accelerating expansion of the universe|acceleration of the expanding universe]], so understanding this relationship will help to refine how [[physicists]] and [[astrophysicists]] understand it. ''Euclid'''s mission advances and complements ESA's [[Planck telescope]] (2009 to 2013). The mission is named after the [[Ancient Greece|ancient Greek]] mathematician [[Euclid]].

''Euclid'' is a medium-class ("M-class") mission and is part of the [[Cosmic Vision]] campaign of ESA's [[European Space Agency Science Programme|Science Programme]]. This class of missions have an ESA budget cap at around €500 million. ''Euclid'' was chosen in October 2011 together with [[Solar Orbiter]], out of several competing missions.<ref>{{cite web|url=http://sci.esa.int/euclid/45403-mission-status/ |title=Mission Status|publisher=[[European Space Agency]]|access-date=23 November 2015}}</ref> ''Euclid'' was launched by a [[Falcon 9 Block 5|Falcon 9]].<ref name="sn-20221020">{{cite web |last=Foust |first=Jeff |url=https://spacenews.com/esa-moves-two-missions-to-falcon-9/ |title=ESA moves two missions to Falcon 9 |work=[[SpaceNews]] |date=20 October 2022 |access-date=20 October 2022}}</ref><ref name="nxsf-euclid"/>

On 7 November 2023 ESA revealed ''Euclid'' 's first full-colour images of the cosmos. The telescope has created razor-sharp astronomical images across a large patch of the sky, looking far into the distant universe. The first five images illustrate ''Euclid'' 's full potential to create the most extensive 3D map of the universe yet.<ref name="NYT-20231107">{{cite news |last=Miller |first=Katrina |title=Euclid Telescope Dazzles With Detailed First Images of Our Universe - The European Space Agency's premier telescope captured new views of space, a small taste of what it is likely to accomplish in the coming years. |url=https://www.nytimes.com/2023/11/07/science/euclid-telescope-photos.html |date=7 November 2023 |work=[[The New York Times]] |url-status=live |archive-url=https://archive.today/20231107143123/https://www.nytimes.com/2023/11/07/science/euclid-telescope-photos.html |archive-date=7 November 2023 |access-date=8 November 2023 }}</ref><ref>{{cite web | url=https://www.esa.int/Science_Exploration/Space_Science/Euclid/Euclid_s_first_images_the_dazzling_edge_of_darkness | title=Euclid's first images: The dazzling edge of darkness }}</ref>

In May 2024, ESA's Euclid mission released images of galaxy clusters [[Abell 2390]] and Abell 2764, star-forming region [[Messier 78]], spiral galaxy [[NGC 6744]], and the [[Dorado Group|Dorado group]] of galaxies. These early observations demonstrate Euclid's capability to study dark matter and cosmic evolution.<ref>{{Cite web |title=ESA's Euclid celebrates first science with sparkling cosmic views |url=https://www.esa.int/Science_Exploration/Space_Science/Euclid/ESA_s_Euclid_celebrates_first_science_with_sparkling_cosmic_views |access-date=2024-05-23 |website=www.esa.int |language=en}}</ref>

==Scientific objectives and methods==
''Euclid'' will probe the history of the [[expansion of the universe]] and the [[Structure formation|formation of cosmic structures]] by measuring the redshift of [[Galaxy|galaxies]] out to a value of 2, which is equivalent to seeing back 10 billion years into the past.<ref name="science">{{Cite web|url=https://sci.esa.int/web/euclid/-/42267-science|title=ESA Science & Technology – Science Goals|website=sci.esa.int}}</ref> The link between galactic shapes and their corresponding redshift will help to show how dark energy contributes to the increased acceleration of the universe. The methods employed exploit the phenomenon of [[gravitational lens]]ing, measurement of [[baryon acoustic oscillations]], and measurement of galactic distances by [[spectroscopy]].<ref>{{Cite web|url=https://sci.esa.int/web/euclid/-/what-are-baryonic-acoustic-oscillations-|title=ESA Science & Technology – What are baryonic acoustic oscillations?|website=sci.esa.int}}</ref>

[[Gravitational lens]]ing (or gravitational shear) is a consequence of the deflection of light rays caused by the presence of matter that locally modifies the [[general relativity|curvature of space-time]]: light emitted by galaxies, and therefore observed images, are distorted as they pass close to matter lying along the line of sight. This matter is composed partly of visible galaxies but it is mostly [[dark matter]]. By measuring this {{Em|shear}}, the amount of dark matter can be inferred, furthering the understanding of how it is distributed in the [[universe]].<ref>{{Cite web|url=https://sci.esa.int/web/euclid/-/what-is-gravitational-lensing-|title=ESA Science & Technology – What is gravitational lensing?|website=sci.esa.int}}</ref>

[[Spectroscopy|Spectroscopic]] measurements will permit measuring the redshifts of galaxies and determining their distances using [[Hubble's law]]. In this way, one can reconstruct the three-dimensional distribution of galaxies in the [[universe]].<ref name="science"/>

From these data, it is possible to simultaneously measure the statistical properties concerning the distribution of dark matter and galaxies and measure how these properties change as the spacecraft looks further back in time. Highly precise images are required to provide sufficiently accurate measurements. Any distortion inherent in the sensors must be accounted for and calibrated out, otherwise the resultant data would be of limited use.<ref name="science"/>

==Spacecraft==
[[File:Euclid Spacecraft in Cleanroom (PIA25783) (cropped).jpg|thumb|''Euclid'' in a cleanroom]]
''Euclid'' emerged from two mission concepts that were proposed in response to the ESA Cosmic Vision 2015–2025 Call for Proposals, issued in March 2007: DUNE, the Dark Universe Explorer, and SPACE, the Spectroscopic All-Sky Cosmic Explorer. Both missions proposed complementary techniques to measure the geometry of the universe, and after an assessment study phase, a combined mission resulted. The new mission concept was called Euclid, honouring the Greek mathematician [[Euclid of Alexandria]] (~300 BC), who is considered the father of geometry. In October 2011, ''Euclid'' was selected by [[European Space Agency|ESA's]] Science Programme Committee for implementation, and on 25 June 2012 it was formally adopted.<ref name="overview"/>

[[European Space Agency|ESA]] selected [[Thales Alenia Space]]'s Italian division for the construction of the satellite in [[Turin]]. ''Euclid'' is 4.5 metres long with a diameter of 3.1 metres and a mass of 2 tonnes.<ref name="new-fact-sheet" />

Meanwhile, the ''Euclid'' payload module was the responsibility of [[Airbus Defence and Space]]'s French division in [[Toulouse]]. It consists of a Korsch telescope with a primary mirror 1.2 meters in diameter, which covers an area of 0.91&nbsp;[[square degree|deg<sup>2</sup>]].<ref>{{Cite web|url=https://sci.esa.int/web/euclid/-/payload-module|title=ESA Science & Technology – Payload Module|website=sci.esa.int}}</ref><ref>{{Cite web|url=https://sci.esa.int/web/euclid/-/telescope|title=ESA Science & Technology – Telescope|website=sci.esa.int}}</ref>

An international consortium of scientists, the Euclid consortium, comprising scientists from 13 European countries and the United States, provided the visible-light camera (VIS)<ref name="euclid-VIS">{{cite web |url=https://sci.esa.int/web/euclid/-/euclid-vis-instrument |title=Euclid VIS Instrument |publisher=[[ESA]] |date=18 October 2019 |access-date=9 July 2020}}</ref> and the [[near-infrared]] [[spectrometer]] and [[photometer]] (NISP).<ref name="euclid-NISP">{{cite web |url=https://sci.esa.int/web/euclid/-/euclid-nisp-instrument |title=Euclid NISP Instrument |publisher=[[ESA]] |date=19 September 2019 |access-date=9 July 2020}}</ref> Together, they will map the 3D distribution of up to two billion galaxies spread over more than a third of the whole sky.<ref>{{cite web |url=http://www.esa.int/Science_Exploration/Space_Science/Thales_Alenia_Space_kicks_off_Euclid_construction |title=Thales Alenia Space kicks off Euclid construction |website=esa.int |date=8 July 2013}}</ref> These large-format cameras will be used to characterise the [[Morphometrics|morphometric]], [[Photometry (astronomy)|photometric]] and spectroscopic properties of galaxies.

=== Instruments ===
* VIS, a camera operating at [[visible spectrum|visible wavelengths]] (530–920&nbsp;nm) made of a mosaic of {{resx|6|6}} [[e2v]] [[charge-coupled device|charge coupled detectors]], containing 600 million pixels, allows measurement of the deformation of galaxies<ref>{{Cite web|url=https://sci.esa.int/web/euclid/-/euclid-vis-instrument|title=ESA Science & Technology – Euclid VIS instrument|website=sci.esa.int}}</ref>
* NISP, a camera composed of a mosaic of 4&nbsp;×&nbsp;4 [[Teledyne]] H2RG detectors sensitive to [[infrared|near-infrared]] light radiation (920–2020&nbsp;nm) with 65 million pixels, is designed for the following:
# provide low-precision measurements of redshifts, and thus distances, of over a billion galaxies from multi-color (3-filter (Y, J and H)) [[Photometry (astronomy)|photometry]] ([[photometric redshift]] technique); and
# use a [[slitless spectrometer]] to analyse the spectrum of light in [[Infrared|near-infrared]] (920–1850&nbsp;nm), to acquire precise [[Reddit|redshifts]] and distances of millions of galaxies with an accuracy 10 times better than [[photometric redshift]]s, and to determine the [[baryon acoustic oscillations]].<ref>{{Cite web|url=https://sci.esa.int/web/euclid/-/euclid-nisp-instrument|title=ESA Science & Technology – Euclid NISP instrument|website=sci.esa.int}}</ref>

=== Spacecraft bus ===
[[File:Euclid spacecraft ESA24912474.jpg|thumb|''Euclid'' spacecraft]]
[[File:Euclid’s_sunny_side_ESA24912429.jpg|thumb|''Euclid''{{'}}s solar panel]]
The telescope bus includes [[solar panel]]s that provide power and stabilise the [[Spacecraft attitude control|orientation]] and pointing of the telescope to better than 35 [[milliarcseconds]] (170&nbsp;nrad). The telescope is carefully insulated to ensure good thermal stability so as to not disturb the optical alignment.{{Citation needed|date=July 2023}}

The telecommunications system is capable of transferring 850 [[gigabits]] per day. It uses the [[Ka band]] and [[CCSDS File Delivery Protocol]] to send scientific data at a rate of 55 megabits per second during the allocated period of 4 hours per day to the 35&nbsp;m dish [[Cebreros Station|Cebreros ground station]] in Spain, when the telescope is above the horizon. ''Euclid'' has an onboard storage capacity of 4 terabits (500&nbsp;[[gigabyte|GB]]).<ref>{{cite web |title=Euclid launch kit |url=https://esamultimedia.esa.int/docs/science/Euclid-LaunchKit.pdf |website=European Space Agency |page=7 |access-date=24 May 2024}}</ref>

The service module (SVM) hosts most of the spacecraft subsystems:{{Citation needed|date=July 2023}}

* TT&C – Telemetry and Telecommand
* AOCS – Attitude Orbit Control System
* CDMS – Central Data Management System
* EPS – Electrical Power System
* RCS – Reaction Control System 
* MPS – Micro-Propulsion System

AOCS provides stable pointing with a dispersion beneath 35 milli-arcseconds per visual exposure. A high thermal stability is required to protect the telescope assembly from optical misalignments at those accuracies.<ref name="auto">{{Cite web|url=https://sci.esa.int/web/euclid/-/service-module|title=ESA Science & Technology – Service Module|website=sci.esa.int}}</ref>

== Milestones ==
[[NASA]] signed a [[memorandum of understanding]] with [[European Space Agency|ESA]] on 24 January 2013 describing its participation in the mission. NASA provided 20 detectors for the near-infrared band instrument, which operate in parallel with a camera in the visible-light band. The instruments, the telescope, and the satellite were built in and are operated from Europe. NASA has also appointed 40 American scientists to be part of the Euclid consortium, which will develop the instruments and analyse the data generated by the mission. Currently, this consortium brings together more than 1000 scientists from 13 European countries and the United States.<ref>{{cite web|url=http://www.esa.int/Space_in_Member_States/Spain/La_NASA_participara_en_la_mision_de_la_ESA_para_estudiar_el_lado_oscuro_del_Universo|title=La NASA participará en la misión de la ESA para estudiar el lado oscuro del Universo|website=esa.int|language=es|date=24 January 2013}}</ref>

In 2015, ''Euclid'' passed a preliminary design review, having completed a large number of technical designs as well as built and tested key components.<ref>{{cite web |url=http://www.esa.int/Our_Activities/Space_Science/Euclid_dark_Universe_mission_ready_to_take_shape|title=Euclid dark Universe mission ready to take shape|publisher=[[ESA]]|date=17 December 2015|access-date=17 December 2015}}</ref>

In December 2018, ''Euclid'' passed its critical design review, which validated the overall spacecraft design and mission architecture plan, and final spacecraft assembly was allowed to commence.<ref name="Arianespace">{{cite web|url=http://www.esa.int/Science_Exploration/Space_Science/Arianespace_and_ESA_announce_the_Euclid_satellite_s_launch_contract_for_dark_energy_exploration|title=Arianespace and ESA announce the Euclid satellite's launch contract for dark energy exploration|website=esa.int|date=7 January 2020}}</ref>

In July 2020, the two instruments (visible and NIR) were delivered to Airbus, Toulouse, France for integration with the spacecraft.<ref>{{Cite web|url=https://www.spacedaily.com/reports/The_Euclid_space_telescope_is_coming_together_999.html|title=The Euclid space telescope is coming together|website=Space Daily}}</ref>

After Russia withdrew in 2022 from the Soyuz-planned launch of ''Euclid'', the [[European Space Agency|ESA]] reassigned it to a SpaceX Falcon 9 launch vehicle, which launched on 1 July 2023 from [[Cape Canaveral Space Launch Complex 40]].<ref name="sn-20221020" /><ref>{{Citation |title=ESA Euclid Mission | date=July 2023 |url=https://www.youtube.com/watch?v=NIwvwYVUuxg |access-date=1 July 2023 |language=en}}</ref><ref name="launch"/>

==Mission execution and data==
[[File:L2 rendering.jpg|thumb|''Euclid'' is orbiting the {{L2}} Lagrange point]]
Following a travel time of 30 days after launch, it began to orbit the Sun-Earth [[Lagrangian point|Lagrangian point L2]]<ref name="new-fact-sheet" /> in an eclipse-free [[halo orbit]] about 1 million km wide.

Upon receiving the initial images, a problem surfaced as scientists discovered a small gap in the spacecraft's hull. This gap allowed sunlight to infiltrate the imaging sensor, resulting in a degradation of image quality.<ref>{{Cite web |last=Quach |first=Katyanna |title=ESA's Euclid telescope beams back first test images |url=https://www.theregister.com/2023/08/02/euclid_telescope_test_images/ |access-date=2023-11-16 |website=www.theregister.com |language=en}}</ref> To tackle this issue, the team adjusted the spacecraft's orientation by a few degrees, effectively blocking sunlight from entering the identified gap. This corrective measure successfully resolved the problem.<ref>{{Cite web |last=Sullivan |first=Will |title=See the First Stunning Test Images From the Euclid Space Telescope |url=https://www.smithsonianmag.com/smart-news/see-the-first-stunning-test-images-from-the-euclid-space-telescope-180982635/ |access-date=2023-11-16 |website=Smithsonian Magazine |language=en}}</ref>

[[File:Euclid begins its dark Universe survey ESA25479326.jpg|thumb|The areas ''Euclid'' will cover during its nominal six-year mission]]

During its nominal mission, which will last at least six years, ''Euclid'' will observe about 15,000&nbsp;deg<sup>2</sup> (4.6&nbsp;sr), about a third of the sky, focusing on the extragalactic sky (the sky facing away from the [[Milky Way]]).<ref name="ecSpacecraft"/> It will generate approximately 100 gigabytes of compressed data per day throughout its six-year mission.<ref>{{Cite web |title=Euclid calling: downloading the Universe |url=https://www.esa.int/Enabling_Support/Operations/Euclid_calling_downloading_the_Universe |access-date=2023-11-16 |website=www.esa.int |language=en}}</ref> The survey will be complemented by additional observations of three deep fields to 5 times the [[Signal-to-noise ratio|signal-to-noise]] of the wide survey; the deep fields cover 50&nbsp;deg<sup>2</sup> (15.2&nbsp;msr).<ref>{{cite web|title=Three Dark Fields for Euclid's Deep Survey|date=12 June 2019|url=https://sci.esa.int/web/euclid/-/61403-three-dark-fields-for-euclid-deep-survey|publisher=ESA|access-date=11 December 2022}}</ref> The three fields will be regularly visited during the whole duration of the mission. They will be used as calibration fields and to monitor the telescope and instrument performance stability as well as to produce scientific data by observing the most distant galaxies and [[quasars]] in the universe.<ref>{{Cite web|title=Surveys|url=https://www.euclid-ec.org/public/data/surveys|access-date=5 August 2023|website=Euclid Consortium}}</ref> Two of the deep fields will overlap with deep fields of existing surveys<ref>{{cite web|title=Three Dark Fields for Euclid's Deep Survey|date=12 June 2019|url=https://sci.esa.int/web/euclid/-/61403-three-dark-fields-for-euclid-deep-survey|publisher=ESA|access-date=8 January 2024}}</ref> and the third deep field is proposed as a location for one of the LSST deep drilling fields at the [[Vera C. Rubin Observatory]].<ref>{{Cite web|title=SCOC endorsement of Euclid Deep Field South observations|date=23 March 2022|url=https://community.lsst.org/t/scoc-endorsement-of-euclid-deep-field-south-observations/6406|access-date=8 January 2024|website=Vera C. Rubin Observatory}}</ref>

To measure a photometric redshift for each galaxy with sufficient accuracy, the ''Euclid'' mission depends on additional photometric data obtained in at least four filters at optical wavelengths. This data will be obtained from ground-based telescopes located in both northern and southern hemispheres to cover the full 15,000&nbsp;deg<sup>2</sup> of the mission.<ref>{{cite book | arxiv=1610.05508 | doi=10.1117/12.2230762 | chapter=The Euclid mission design | title=Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave | year=2016 | editor-last1=MacEwen | editor-last2=Fazio | editor-last3=Lystrup | editor-last4=Batalha | editor-last5=Siegler | editor-last6=Tong | editor-first1=Howard A. | editor-first2=Giovanni G. | editor-first3=Makenzie | editor-first4=Natalie | editor-first5=Nicholas | editor-first6=Edward C. | last1=Racca | first1=Giuseppe D. | last2=Laureijs | first2=René | last3=Stagnaro | first3=Luca | last4=Salvignol | first4=Jean-Christophe | last5=Lorenzo Alvarez | first5=José | last6=Saavedra Criado | first6=Gonzalo | last7=Gaspar Venancio | first7=Luis | last8=Short | first8=Alex | last9=Strada | first9=Paolo | last10=Bönke | first10=Tobias | last11=Colombo | first11=Cyril | last12=Calvi | first12=Adriano | last13=Maiorano | first13=Elena | last14=Piersanti | first14=Osvaldo | last15=Prezelus | first15=Sylvain | last16=Rosato | first16=Pierluigi | last17=Pinel | first17=Jacques | last18=Rozemeijer | first18=Hans | last19=Lesna | first19=Valentina | last20=Musi | first20=Paolo | last21=Sias | first21=Marco | last22=Anselmi | first22=Alberto | last23=Cazaubiel | first23=Vincent | last24=Vaillon | first24=Ludovic | last25=Mellier | first25=Yannick | last26=Amiaux | first26=Jérôme | last27=Berthé | first27=Michel | last28=Sauvage | first28=Marc | last29=Azzollini | first29=Ruyman | last30=Cropper | first30=Mark | volume=9904 | pages=99040O | s2cid=118513194 | display-authors=1 }}</ref><ref>{{cite book | chapter-url=https://arc.aiaa.org/doi/pdf/10.2514/6.2018-2433 | doi=10.2514/6.2018-2433 | chapter=Euclid Science Ground Segment (SGS) Processing Operations Concept | title=2018 SpaceOps Conference | year=2018 | last1=Poncet | first1=Maurice | last2=Dabin | first2=Christophe | last3=Buenadicha | first3=Guillermo | last4=Hoar | first4=John | last5=Zacchei | first5=Andrea | last6=Sauvage | first6=Marc | isbn=978-1-62410-562-3 }}</ref> In total each galaxy of the ''Euclid'' mission will get photometric information in at least seven different filters covering the whole range 460–2000&nbsp;nm.<ref name="eoportal.org">{{cite web | url=https://www.eoportal.org/satellite-missions/euclid | title=Euclid – Mapping the Geometry of the Dark Universe Mission }}</ref>

About 10 billion astronomical sources will be observed by ''Euclid'', of which one billion will be used for [[weak lensing]] (to have their gravitational shear measured)<ref name="consortium"/> with a precision 50 times more accurate than is possible today using ground-based telescopes. ''Euclid'' will measure spectroscopic redshifts for at least 30 million objects to study [[galaxy clustering]].

The scientific exploitation of this enormous data set will be carried out by a European-led consortium of more than 1200 people in over 100 laboratories in 18 countries (Austria, Belgium, Denmark, Finland, France, Germany, Italy, the Netherlands, Norway, Portugal, Romania, Spain, Switzerland, UK, Canada, US, and Japan).<ref>{{cite web |title=About the Euclid Consortium and membership |url=https://www.euclid-ec.org/consortium/about-ec/ |website=Euclid Consortium |access-date=3 July 2023 |date=15 April 2023}}</ref> The Euclid Consortium<ref name="consortium">{{Cite web|url=https://www.euclid-ec.org/|title=Euclid Consortium – A space mission to map the Dark Universe}}</ref> is also responsible for the construction of the ''Euclid'' instrument payload and for the development and implementation of the Euclid [[ground segment]] which will process all data collected by the satellite. The laboratories contributing to the Euclid Consortium are funded and supported by their national space agencies, which also have the programmatic responsibilities of their national contribution, and by their national research structures (research agencies, observatories, universities). Overall, the Euclid Consortium contributes to about 25% of the total budget cost of the mission until completion.<ref>{{cite web | url=https://spaceflightnow.com/news/n1206/20euclid/ | title=Spaceflight Now &#124; Breaking News &#124; ESA's Euclid mission cleared to proceed into development }}</ref>

The huge volume, diversity (space and ground, visible and near-infrared, [[Morphometrics|morphometry]], photometry, and spectroscopy) and the high level of precision of measurements demanded considerable care and effort in the data processing, making this a critical part of the mission. [[ESA]], the national agencies and the Euclid Consortium are spending considerable resources to set up top-level teams of researchers and engineers in algorithm development, software development, testing and validation procedures, data archiving and data distribution infrastructures. In total, nine Science Data Centres spread over countries of the Euclid Consortium will process more than 170 [[petabyte]]s of raw input images over at least 6 years to deliver data products (images, catalogues spectra) in three main public data releases in the Science Archive System of the ''Euclid'' mission to the scientific community.<ref>{{cite web | url=https://reportdome.com/panoramic-information-euclid-space-telescope-unveiling-the-secrets-of-the-dark-universe-day-03-07-2023 | title=Panoramic Information Euclid Space Telescope: Unveiling the Secrets of the Dark Universe day 03/07/2023 – Reportdome | date=3 July 2023 | access-date=7 July 2023 | archive-date=21 July 2023 | archive-url=https://web.archive.org/web/20230721175338/https://reportdome.com/panoramic-information-euclid-space-telescope-unveiling-the-secrets-of-the-dark-universe-day-03-07-2023 | url-status=dead }}</ref><ref name="eoportal.org"/>

With its wide sky coverage and its catalogues of billions of [[star]]s and galaxies, the scientific value of data collected by the mission goes beyond the scope of [[cosmology]]. This database will provide the worldwide astronomical community with abundant sources and targets for the [[James Webb Space Telescope]] and [[Atacama Large Millimeter Array]], as well as future missions such as the [[European Extremely Large Telescope]], [[Thirty Meter Telescope]], [[Square Kilometer Array]], and the [[Vera C. Rubin Observatory]].<ref>{{Cite web|url=https://sci.esa.int/web/euclid/-/legacy-science-beyond-cosmology|title=ESA Science & Technology – Legacy science (beyond cosmology)|website=sci.esa.int}}</ref>

{{multiple image
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| direction = horizontal
| width = 350px
| header = Animation of Euclid
| image1 = Animation of Euclid around Earth.gif
| caption1 = Around the Earth
| image2 = Animation of Euclid around Sun - Frame rotating with Earth - Top view.gif
| caption2 = Around the Sun – Frame rotating with Earth – Top view
| image3 = Animation of Euclid around Sun - Frame rotating with Earth - Viewed from Sun.gif
| caption3 = Around the Sun – Frame rotating with Earth – Viewed from the Sun
| footer = {{legend2|Magenta| Euclid}}{{·}}{{legend2| RoyalBlue| Earth}}{{·}}{{legend2|Cyan| Sun-Earth L2}}
}}

== Gallery of first test images ==
<gallery mode=packed heights=180px>
File:How_Euclid_scans_the_sky_ESA24913466.jpg|''Euclid'' scans across the night sky using a 'step-and-stare' method, combining separate measurements to form the largest cosmological survey ever conducted in the visible and near-infrared.
File:Early commissioning test image VIS instrument (1).png|Early commissioning test image VIS instrument
File:Early commissioning test image NISP instrument (1).png|Early commissioning test image NISP instrument
File:Early commissioning test image NISP instrument grism mode.png|Early commissioning test image NISP instrument [[grism]] mode
</gallery>

Source:<ref>{{cite web |title=Euclid test images tease of riches to come |url=https://www.esa.int/Science_Exploration/Space_Science/Euclid/Euclid_test_images_tease_of_riches_to_come |website=www.esa.int |access-date=31 July 2023 |language=en}}</ref>

== Gallery ==
<gallery>
File:Euclid’s view of the Horsehead Nebula ESA25170866.tiff|''Euclid''{{'}}s view of the [[Horsehead Nebula]].
File:Euclid’s view of the Perseus cluster of galaxies ESA25170535.jpg|''Euclid''{{'}}s view of the [[Perseus Cluster|Perseus cluster]] of galaxies.
File:Euclid’s new image of galaxy cluster Abell 2390 ESA497230.jpg|''Euclid''{{'}}s view of galaxy cluster [[Abell 2390]].
File:Euclid’s new image of spiral galaxy NGC 6744 ESA497254.jpg|''Euclid''{{'}}s view of spiral galaxy [[NGC 6744]].
File:Euclid’s new view of galaxy cluster Abell 2764 ESA497269.jpg|''Euclid''{{'}}s view of galaxy cluster Abell 2764.
File:Euclid’s new image of star-forming region Messier 78 ESA497237.jpg|''Euclid''{{'}}s view of star-forming region [[Messier 78]].
File:Euclid’s_mosaic_explained_ESA502306.jpg|The mosaic and zoomed in images released by ESA’s Euclid mission on 15 October 2024<ref>{{cite web |title=Zoom into the first page of ESA Euclid’s great cosmic atlas |url=https://www.esa.int/Science_Exploration/Space_Science/Euclid/Zoom_into_the_first_page_of_ESA_Euclid_s_great_cosmic_atlas |website=www.esa.int |access-date=22 October 2024 |language=en}}</ref>
</gallery>

==References==
{{Reflist}}

==External links==
{{Commonscat}}
* [http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=42266 ''Euclid'' homepage]
* [https://www.eoportal.org/satellite-missions/euclid ''Euclid'' article on eoPortal by ESA]

{{European Space Agency}}
{{Space observatories}}
{{Orbital launches in 2023}}

{{Use British English|date=January 2014}}

[[Category:European Space Agency space probes]]
[[Category:Space telescopes]]
[[Category:Spacecraft launched in 2023]]
[[Category:Infrared telescopes]]
[[Category:Cosmic Vision]]
[[Category:Dark energy]]
[[Category:Dark matter]]