The Dark Energy Survey (DES) is a survey of various phenomena that reveal the course of the expansion of the universe, including Type Ia supernovae, baryon acoustic oscillations, counts of early galaxy clusters, and weak lensing. Its aim is measuring and confirming the existence of dark energy. It is being carried out by an international collaboration of research institutions. The planned observations are complete, and analysis continues.
Observations were conducted from 2013 to 2019 using the Blanco 4m telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. The size of the survey area is 5000 square degrees, about 1/8 of the sky. The camera (DECam, for Dark Energy Camera) imaged visible light and some near infrared, with about three square degrees per image.
Thousands of supernovae were observed, too many for spectrography during the useful parts of their light curves, so only about a thousand received such treatment (in collaboration with the Anglo-Australian Telescope (AAT) OzDES project, using AAT's multi-object spectrograph, AAOmega with fiber positioner 2dF), the rest analyzed through photometry and identification of the (probable) host galaxy, for which a redshift can be determined later.