Installing the 3.4-meter mirror brings the facility one step closer to first light, set to take place in 2025.
The Vera C. Rubin Observatory’s 3.5-meter secondary mirror is the first piece of glass installed into the telescope in its permanent position. Credit: Rubin Observatory/NSF/AURA/F. Munoz Arancibia
On July 24, 2024, a team at the Vera C. Rubin Observatory in Chile installed its 3.4-meter secondary mirror onto the Simonyi Survey Telescope. Its installment brings the facility one step closer to imaging the southern sky with the largest digital camera in the world.
The secondary mirror (M2) is the first permanent piece of the telescope’s optical system to be installed. After the mirror was built and polished, it was shipped to Chile in 2018 from Rochester, New York. It was stored in the observatory while the telescope’s mount was built over the last several years.
“Working with the mirror again after five years is extremely exciting because it really feels like we’re in the home stretch,” said Sandrine Thomas, deputy director for Rubin Observatory Construction, in a NOIRLab press release. “Now we have glass on the telescope, which brings us a thrilling step closer to revolutionary science with Rubin.”
Related: ‘It’s going to be awesome’: How the Vera C. Rubin Observatory will survey space and time
Piece by piece
According to the press release, the Rubin Observatory’s M2 is one of the largest convex mirrors ever constructed. It measures just under 13 feet (4 meters) in diameter. In 2019, the secondary mirror underwent a four-hour process to coat it with protective silver to increase its durability over its lifetime.
To install the mirror, a team used a cart to rotate it vertically and then lifted it onto the telescope mount while taking care to make sure the glass was not stressed. Once the mirror was in place, team members at the facility in Cerro Pachón activated the mirror control software system.
The next steps for the Rubin Observatory include reinstalling the temporary Commissioning Camera in the coming weeks. This smaller version of the Legacy Survey of Space and Time (LSST) camera will be used to test the telescope’s optical system. Now that the secondary mirror is in place, the focus will be on preparing the primary mirror for installation this month and the LSST camera installment later this year.
Once everything is installed and tested, the decade-long LSST is set to start in 2025. Once online, it will begin mapping the night sky and its changes, bringing researchers closer to deciphering dark matter and dark energy.
Related: ‘It’s going to be awesome’: How the Vera C. Rubin Observatory will survey space and time
