It uses images taken in the near-ultraviolet, visible, and near-infrared to measure the expansion of the universe using Type Ia supernovae, baryon acoustic oscillations, the number of galaxy clusters, and weak gravitational lensing.

[4] The DES began by developing and building Dark Energy Camera (DECam), an instrument designed specifically for the survey.

[5] This camera has a wide field of view and high sensitivity, particularly in the red part of the visible spectrum and in the near infrared.

[6] Observations were performed with DECam mounted on the 4-meter Víctor M. Blanco Telescope, located at the Cerro Tololo Inter-American Observatory (CTIO) in Chile.

These components are attached to the CCD focal plane which is cooled to 173 K (−148 °F; −100 °C) with liquid nitrogen in order to reduce thermal noise in the CCDs.

The focal plane is also kept in an extremely low vacuum of 0.00013 pascals (1.3×10−9 atm) to prevent the formation of condensation on the sensors.

When mounted at the prime focus it was supported with a hexapod system allowing for real time focal adjustment.

[9] The camera is outfitted with u, g, r, i, z, and Y filters spanning roughly from 340–1070 nm,[10] similar to those used in the Sloan Digital Sky Survey (SDSS).

[6] One significant difference between previous charge-coupled devices (CCD) at the Victor M. Blanco Telescope and DECam is the improved quantum efficiency in the red and near-infrared wavelengths.

Scientifically this is important because it allows one to look for objects at a higher redshift, increasing statistical power in the studies mentioned above.

When placed in the telescope's focal plane each pixel has a width of 0.27″ on the sky, resulting in a total field of view of 3 square degrees.

[12] DES imaged 5,000 square degrees of the southern sky in a footprint that overlaps with the South Pole Telescope and Stripe 82 (in large part avoiding the Milky Way).

Longer exposure times and faster observing cadence were made in five smaller patches totaling 30 square degrees to search for supernovae.

[14] First light was achieved on 12 September 2012;[15] after a verification and testing period, scientific survey observations started in August 2013.

Despite the restrictions on each exposure, the team also need to consider different sky conditions for the observations, such as moonlight and cloud cover.

[23] Other cosmological analyses from first year data showed a derivation and validation of redshift distribution estimates and their uncertainties for the galaxies used as weak lensing sources.

[26] From third-year data of Galaxy Clustering and Weak Lensing results, DES updated the Cosmological Constraints to

[31] In April 2015, the Dark Energy Survey released mass maps using cosmic shear measurements of about 2 million galaxies from the science verification data between August 2012 and February 2013.

[32] In 2021 weak lensing was used to map the dark matter in a region of the southern hemisphere sky,[29][30] in 2022 together with galaxy clustering data to give new cosmological constrains.

DES team monitored the source for over two weeks and provide the light curve data as a machine-readable file.

This discovery ushers in the era of multi-messenger astronomy with gravitational waves and demonstrates the power of DECam to identify the optical counterparts of gravitational-wave sources.

[42] In March 2015, two teams released their discoveries of several new potential dwarf galaxy candidates found in Year 1 DES data.

[43] In August 2015, the Dark Energy Survey team announced the discovery of eight additional candidates in Year 2 DES data.

[49] The signature of baryon acoustic oscillations (BAO) can be observed in the distribution of tracers of the matter density field and used to measure the expansion history of the Universe.

[50] DES team observation samples consists of 7 million galaxies distributed over a footprint of 4100 deg2 with 0.6 < zphoto < 1.1 and a typical redshift uncertainty of 0.03(1+z).

[55] In June 2019, there a follow-up paper was published by DES team discussing the systematic uncertainties, and validation of using the supernovae to measure the cosmology results mentioned before.

[57] Several minor planets were discovered by DeCam in the course of The Dark Energy Survey, including high-inclination trans-Neptunian objects (TNOs).

[58] The MPC has assigned the IAU code W84 for DeCam's observations of small Solar System bodies.

As of October 2019, the MPC inconsistently credits the discovery of nine numbered minor planets, all of them trans-Neptunian objects, to either "DeCam" or "Dark Energy Survey".

[68] The list does not contain any unnumbered minor planets potentially discovered by DeCam, as discovery credits are only given upon a body's numbering, which in turn depends on a sufficiently secure orbit determination.