Euclid is an M-class mission of the European Space Agency (ESA), due to launch in 2020. It is a cosmology experiment designed to measure the large scale structure of the Universe with exquisite accuracy. There are two main experiments on board: one is to carry out a redshift survey of distant galaxies. The other is to make a high accuracy weak lensing survey.
There are two imaging systems: a very broad band optical system for making the weak lensing galaxy shape measurements; and an infrared channel for galaxy photometry, combined with a grism slitless spectroscopic survey.
The scientific analysis is being carried out by a consortium of around 1200 European and USA astronomers. For more information on the Euclid Consortium and on the mission see the Consortium pages and the ESA mission pages.