The visible (VIS) instrument (Cropper et al. 2014, Proceedings of the SPIE, Volume 9143, id. 91430J) is a UK responsibility within the Euclid Consortium. VIS will image the sky with high image quality. It will be used to measure the shapes of galaxies and derive the gravitational lensing effects induced by large scale structures of the Universe on galaxies and it will probe how the dark matter is distributed and how this distribution changed over the last 10 billion years. It will also provide a huge legacy data set for general astrophysics.

The different subsystems of the VIS instruments are shown on the image below. The VIS focal plane is composed of a matrix of 6×6 4096×4096 e2v CCDs (Charge Coupled Devices), specially optimised for the Euclid mission (CCD273), covering a field of view of 0.57 deg² (about 180 times the field of view of the Hubble Space Telescope ACS wide field camera) with 0.1 arc-second pixels. It will observe in one broad bandpass covering the wavelength range from 550 to 900nm with a mean image quality of  0.2 arc seconds. VIS will be able to reach a signal-to-noise ratio of at least 10 for 1.5 billion galaxies down to 24.5 magnitude AB.