The most expensive and precise mirror ever built for a NASA space telescope just got its final closeup. Engineers at NASA's Goddard Space Flight Center in Greenbelt, Maryland, gave the Roman Space Telescope's 7.9-foot primary mirror a last look before it ships out for final assembly. This mirror, made of a special glass that barely expands with heat, will be the eye of a telescope designed to see more of the sky in one shot than Hubble ever could.
A mirror that took years to perfect
The primary mirror is the largest piece of the Roman Space Telescope, which is set to launch no earlier than May 2027. It was built by L3Harris Technologies in Rochester, New York, and delivered to Goddard in 2024. Since then, engineers have been testing it in a vacuum chamber that mimics the cold, airless conditions of space. The mirror is coated with a thin layer of silver and a protective layer of silicon dioxide. It weighs about 400 pounds and is made from Corning's Ultra Low Expansion Glass, which barely changes shape when temperatures shift.
Why this telescope matters to astronomers
The Roman Space Telescope, named after NASA's first chief astronomer Nancy Grace Roman, will have a field of view 100 times larger than Hubble's. That means it can survey huge swaths of the sky quickly. Scientists plan to use it to study dark energy, find exoplanets, and map the Milky Way. The mirror's final inspection at Goddard included a series of optical tests to make sure it was perfectly shaped. After those tests passed, the mirror was packed up and shipped to a Ball Aerospace facility in Boulder, Colorado, where it will be integrated with the rest of the telescope.
What happens next
Once the mirror is attached to the telescope structure, the whole assembly will go to NASA's Johnson Space Center in Houston, Texas, for thermal vacuum testing. That will be the last major test before the telescope is shipped to the launch site. The Roman Space Telescope is expected to launch on a SpaceX Falcon Heavy rocket from Cape Canaveral, Florida. For the engineers who have spent years polishing and protecting this mirror, the final look was a quiet milestone before a much bigger journey.
