The Simons Observatory (SO) has completed the installation of its Large Aperture Telescope (LAT) near the summit of Cerro Toco in the Atacama Desert of northern Chile.The telescope joins the observatory’s three Small Aperture Telescopes (SAT) at the site and will collect the most precise measurements yet of the universe’s oldest light — the cosmic microwave background — to help determine what happened just after the universe’s birth.The University of Manchester is a key partner in SO, playing a leading role in the SO:UK project, which is funded by United Kingdom Research and Innovation (UKRI). SO:UK is currently constructing two additional SATs for the observatory, significantly enhancing its observational capabilities. The University also hosts a major data centre dedicated to processing the wealth of data generated by all four SO telescopes.Professor Michael Brown, Head of Cosmology at the Jodrell Bank Centre for Astrophysics and Principal Investigator of the SO:UK project, said: “After eight years of design and construction work, first light for the SO LAT telescope is a major milestone for SO and paves the way for a huge range of exciting science to come over the next decade. Together with data from the first three SO SATs, we are excited to start searching the first LAT observations to reveal new secrets of the Universe.”The LAT receiver camera, measuring 2.4 by 2.6 metres, was carefully installed last year, with the final step being the placement of its two six-metre mirrors. Shortly after completion in late February 2025, the telescope obtained its first celestial image—an observation of Mars. With this successful test, the LAT is set to begin collecting observations in the coming months.SO Co-Director Mark J. Devlin, said: “This work is the culmination of eight years of effort by dozens of SO researchers to make the world’s most capable ground-based cosmology telescope.“At the moment the second mirror went in, we moved to make the first observations with the telescope, and all initial indications point to a huge success.”SO Co-Director Suzanne Staggs, added: “In the space between design and proof of success, there are many sleepless nights, so the LAT’s first light observations are a highly satisfying first step toward proof of the remarkable design.”“To achieve the gamut of the SO science objectives, the SO team designed the LAT and its camera to have unprecedented sensitivity and excellent optical quality.”The LAT and the three SATs will closely measure the cosmic microwave background, which is essentially the afterglow of the Big Bang, as well as observe other targets such as the universe’s most massive black holes and our solar system’s asteroids.“It’s wonderful to have this last major piece of our observatory in place,” says SO Spokesperson Jo Dunkley, the Joseph Henry Professor of Physics and Astrophysical Sciences at Princeton University. “We are excited to find out what the suite of SO telescopes will reveal to us about the universe.”With all four telescopes now online, the software behind SO is now hard at work operating the observatory’s mechanics and managing the influx of data.“The LAT coming online means so is the software that runs it,” says SO Data Manager Simone Aiola. “The software is now controlling the movements of the telescopes, analysing the incoming data and backing everything up to two sites in North America and another in the UK.”Future upgrades to the Simons Observatory are already in the works, including enhancing the sensitivity of the LAT and adding new SATs. These upgrades come thanks to funding from the National Science Foundation, U.K. Research and Innovation, and the Japan Society for the Promotion of Science.The new milestone coincides with the launch of a new Simons Observatory website, which will help communicate the project’s incredible science and technological advances to the public. The SO team also put together a fact sheet chronicling the SO progress through March 2025.
Simons Observatory Large Aperture Telescope achieves first light milestone
