The DES Project

The accelerated expansion of the universe is the main discovery that sets the initial research program of 21st Century cosmology. The Dark Energy Survey is a large sky survey aimed directly at understanding this mystery. The DES Collaboration has built an extremely red sensitive 500 Megapixel camera (DECam), a 1 meter diameter, 2.2 degree field of view prime focus corrector, and a data aquisition system fast enough to take images in 17 seconds. The cage containing the system mounts at the prime focus of the Blanco 4-meter telescope at CTIO, a southern hemisphere NOAO telescope. Over 5 years, a 30% of the available time on the telescope will be used to pursue a high precision multi-bandpass wide area survey, designed to produce photometric redshifts from 0.2 < z < 1.3. The survey g,r,i,z,Y data will cover 5000 sq-degrees. The 4 main science goals aim at extracting cosmological information on the dark energy from:

• Cluster counting and spatial distribution of clusters at 0.1 < z < 1.3,
• The shifting of the galaxy spatial angular power spectra with redshift,
• Weak lensing measurements on several redshift shells to z~1,
• 4000 supernovae at 0.3 < z < 0.8.

The signature of dark energy being a cosmological constant is that the dark energy density remains constant while the universe expands; technically that w=-1 and that dw/dt = 0. We aim at a 5%-15% precision measurement in w from each of our probes, and a 30% measurment in w'. Combined, they provide both stronger constraints and a check on systematic errors.