DESI completes its five-year mission with the largest 3D map of the universe ever made

In the early hours of April 15, 2026, the 5,000 fiber-optic eyes of the Dark Energy Spectroscopic Instrument pointed toward a patch of sky near the Little Dipper. Every twenty minutes or so, they locked onto distant pinpricks of light — photons that had been traveling toward Earth for billions of years. When the sun rose, the DESI collaboration marked the completion of one of the most ambitious observational programs in the history of cosmology: the full five-year survey of the universe.

The result is the largest high-resolution three-dimensional map of the cosmos ever produced.

Beyond all expectations

When DESI began collecting data in May 2021, the original goal was to observe 34 million galaxies and quasars over five years. The instrument exceeded that target by a wide margin. By the time observations concluded, DESI had recorded more than 47 million galaxies and quasars — highly luminous objects powered by supermassive black holes — along with more than 20 million nearby stars within the Milky Way. Altogether, the survey has measured cosmological data for six times as many objects as all previous measurements combined.

The survey was completed ahead of schedule and delivered significantly more data than originally projected. This outcome is all the more remarkable given the obstacles the collaboration faced along the way. In 2020, the COVID-19 pandemic interrupted final commissioning tests. In 2022, the Contreras Fire swept across Kitt Peak National Observatory in Arizona, where DESI is mounted on the Nicholas U. Mayall 4-meter Telescope. Thanks to the efforts of firefighters and observatory staff, the telescope was not damaged, though recovery was slowed by subsequent monsoons and mudslides.

«DESI is a complicated but wonderfully robust system, and it’s been a huge amount of fun to see it come together and work so well for such a long time,» said Connie Rockosi, co-instrument scientist for DESI and professor at UC Santa Cruz and UC Observatories.

An engineering feat, one galaxy at a time

The technical backbone of DESI is a set of 5,000 robotic positioners, each carrying a fiber-optic cable. These positioners are accurate to within 10 microns — less than the width of a human hair — allowing the instrument to simultaneously point at thousands of objects across the sky. Ten spectrographs then split the gathered light into its component colors, which encode each object’s distance, velocity, and chemical composition.

Each night, roughly 80 gigabytes of raw data flow from the telescope through DOE’s high-speed research network to supercomputers at the National Energy Research Scientific Computing Center (NERSC) at Berkeley Lab. Researchers spent five years continuously refining telescope operations, software, hardware calibrations, and observing protocols to maximize efficiency. DESI ultimately completed five full passes of its footprint during the Bright-Time Survey — carried out when moonlight hampers observations of faint objects — and seven passes during the Dark-Time Survey. The total coverage spans approximately two-thirds of the northern night sky, or roughly 14,000 square degrees.

«There’s been constant monitoring and intervention to make the whole thing tick,» said Adam Myers, co-manager of DESI’s survey operations and professor at the University of Wyoming. «The DESI team is remarkable. This huge group of people have all been working on whether they could save one or two or three percent in their particular area, and when you add it all up, it results in these amazing gains in efficiency.»

A window onto dark energy

The primary scientific driver behind DESI is dark energy, the mysterious component that makes up approximately 70% of the total energy content of the universe and is responsible for its accelerating expansion. By analyzing the three-dimensional distribution of galaxies at different epochs, researchers can use a technique known as baryon acoustic oscillations (BAO) to measure how the expansion rate of the universe has changed over time — effectively tracing dark energy’s influence across 11 billion years of cosmic history.

Surprising results from DESI’s first three years of data hinted that dark energy, long assumed to be a fixed cosmological constant as Einstein originally proposed, may in fact be evolving over time. If that hint is confirmed by the full five-year dataset, it would represent a profound revision of our standard cosmological model and would have deep implications for the ultimate fate of the universe.

The DESI collaboration will immediately begin processing the completed dataset. The first dark energy results from the full five-year survey are expected in 2027. In the meantime, several papers based on the three-year dataset are planned for release later this year.

«DESI’s five-year survey has been spectacularly successful,» said Michael Levi, DESI director and scientist at Berkeley Lab. «The instrument performed better than anticipated. The results have been incredibly exciting. And the size and scope of the map and how quickly we’ve been able to execute it is phenomenal.»

The map keeps growing

Despite having completed its original survey plan, DESI is not finished. Observations are continuing and will extend through 2028, expanding the map by roughly 20% — from 14,000 to approximately 17,000 square degrees. For context, the full sky spans just over 41,000 square degrees; the Moon covers a mere 0.2.

The extended survey will push into more challenging regions: areas closer to the plane of the Milky Way, where bright foreground stars complicate measurements of distant objects, and regions farther to the south, where observations must contend with thicker layers of Earth’s atmosphere. DESI will also revisit existing areas of the map to collect data from a new population of targets — luminous red galaxies that are more distant and faint — providing a denser and more detailed picture of cosmic structure.

Researchers are also planning observations of nearby dwarf galaxies and stellar streams, which are bands of stars stripped from smaller satellite galaxies by the Milky Way’s gravitational pull. These targets will help constrain models of dark matter, the invisible form of matter that accounts for most of the mass in the universe but has never been directly detected.

DESI is a global collaboration involving more than 900 researchers — including approximately 300 PhD students — from over 70 institutions. The project is managed by the Department of Energy’s Lawrence Berkeley National Laboratory.

«We’ve built a remarkable piece of equipment that met all our expectations and then some,» Levi said. «Now we’re pushing beyond our original plan.»

A universe mapped. And the questions multiplying.

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© 2026 SKYCR.ORG | Homer Dávila Gutiérrez, FRAS. All rights reserved. Reproduction in whole or in part without express authorization is prohibited. Original source: Lawrence Berkeley National Laboratory — https://newscenter.lbl.gov/2026/04/15/desi-completes-planned-3d-map-of-the-universe-and-continues-exploring/