Euclid is the ESA satellite launched on 1 July 2023 with the primary aim of studying the composition and evolution of our universe. To do so, it will observe more than a billion galaxies in photometry, and will also obtain slitless spectra for tens of millions of them. This is possible thanks to the two instruments mounted on board: VIS, which observes in the optical, and NISP, which observes and acquires spectra in the near infrared.

Euclid will perform two surveys, one called WIDE that will observe about 14,000 square degrees of sky and one called DEEP that will observe 53 square degrees at a greater depth both photometrically (about two magnitudes) and spectroscopically (about a factor of 5 in line flux).