The Mayall 4-meter telescope at Kitt Peak National Observatory in Arizona has been operating for 45 years as an important research telescope. But it is getting a major makeover as scientists reconfigure it so that it can hunt for dark matter and help unlock one of the most mysterious forces in the universe.

A new instrument called the Dark Energy Spectroscopic Instrument (DESI) will be installed on the telescope as part of the reconfiguration, which began on Monday and is expected to last more than a year. After that, scientists will use the DESI instrument to collect spectra, or the separation of light, of 30 million galaxies.

Scientists are hoping to better understand changes in the expansion rate of the universe, which could help unlock some of the deepest mysteries of existence itself. Scientists had thought for a while that the universe began expanding more and more quickly ever since the big bang, but recently came to the surprising discovery that the universe expanded at a constant rate for while before suddenly accelerating a few billion years ago.

“When the Mayall first opened its eye to the sky 45 years ago, it was one of the largest optical telescopes in existence,” reads a statement from the Association of Universities for Research in Astronomy. “Designed to be versatile, its mission was to assist astronomers in addressing the wide diversity of astronomical questions facing the field. Tremendously successful, it played an important role in many astronomical discoveries, such as establishing the role of dark matter in the Universe from measurements of galaxy rotation, and determining the scale and structure of the Universe.”