Euclid is a wide-angle space telescope with a 600-megapixel camera to record 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.

Euclid is a medium-class ("M-class") mission and is part of the Cosmic Vision campaign of ESA's Science Programme.

[17] The link between galactic shapes and their corresponding redshift will help to show how dark energy contributes to the increased acceleration of the universe.

[18] Gravitational lensing (or gravitational shear) is the alteration of the trajectories of light rays caused by the presence of matter that locally modifies the curvature of space-time: light emitted by galaxies is deflected as it passes close to matter lying along the line of sight, distorting the resulting image.

In October 2011, Euclid was selected by ESA's Science Programme Committee for implementation, and on 25 June 2012 it was formally adopted.

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 m dish Cebreros ground station in Spain, when the telescope is above the horizon.

[25] The service module (SVM) hosts most of the spacecraft subsystems:[citation needed] AOCS provides stable pointing with a dispersion beneath 35 milli-arcseconds per visual exposure.

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.

Upon receiving the initial images, a problem surfaced as scientists discovered a small gap in the spacecraft's hull.

[32] To tackle this issue, the team adjusted the spacecraft's orientation by a few degrees, effectively blocking sunlight from entering the identified gap.

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.

This data will be obtained from ground-based telescopes located in both northern and southern hemispheres to cover the full 15,000 deg2 of the mission.

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).

[51] The huge volume, diversity (space and ground, visible and near-infrared, 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.

[52][48] With its wide sky coverage and its catalogues of billions of stars and galaxies, the scientific value of data collected by the mission goes beyond the scope of cosmology.