Free Astronomy Magazine September-October 2026

37 SEPTEMBER-OCTOBER 2026 ASTRO PUBLISHING a human hair. The silver coat- ing was specifically chosen for Roman because of how well it reflects near-infrared light. By contrast, the Hubble Space Telescope’s mirror is coated with layers of alu- minum and magnesium fluo- ride to optimize visible and ultraviolet light reflectivity. Likewise, the James Webb Space Telescope’s mirrors have a gold coating to suit its longer wavelength infrared observations. The Roman mirror is so finely polished that the average bump on its surface is only 1.2 nanometers tall — more than twice as smooth as the mission requires. If the mirror were scaled up to Earth’s size, these bumps would be just a quarter of an inch high. Since it’s made of a special- ty ultralow-expansion glass, the mirror will resist flexing, which can happen to mate- rials during temperature changes (like going from bal- my Earth conditions to the deep freeze of space). This preserves Roman’s im- age quality, because if the primary mirror changed shape, it would distort the images from the telescope. “We’re really proud of the amazing optical system we have delivered for the Ro- man mission alongside our partners at L3-Harris,” said Josh Abel, lead Optical Telescope Assembly systems engineer at NASA Goddard. “Now that it’s assembled, aligned, and all cleaned up, we’re ready to ship the instrument to the launch site at NASA’s Kennedy Space Center in Florida.” NASA expects the mission to begin returning incredible cos- mic vistas within several months after launch. E ngineers at NASA’s God- dard Space Flight Center in Greenbelt, Maryland, have completed their final in- spection of a key element for the agency’s Nancy Grace Roman Space Telescope: the primary mirror. This 7.9-foot (2.4-meter) mirror will collect and focus light from cosmic objects near and far, helping Roman capture stunning pan- oramas of space. “The Roman engineering team laid eyes on the telescope for the final time before it, in turn, be- comes the eyes of humanity, revealing the wonders of the cosmos,” said J. Scott Smith, the Roman telescope manager at NASA Goddard. “It is a pro- foundly humbling moment to witness the culmination of hard work from so many ded- icated individuals, teams, and partner organizations, includ- ing L3Harris.” On May 20, engineers turned the Roman observatory onto its side and deployed the “hood” that will be stowed for launch to protect the mir- ror. Then the team conducted a meticulous visual inspection to ensure no specks fell onto the mirrors during testing and confirm there are no changes in the mirror path and alignment. “We developed a method of using a high-resolution camera e- quipped with a very powerful zoom lens to do a multi-purpose inspec- tion,” said Bente Eegholm, optics lead for Roman’s Optical Telescope Assembly at NASA Goddard. “The mirror passed with flying colors, keeping the mission on track for an early September launch.” The team carefully observed the op- tics along the path light will follow to the Wide Field Instrument detec- T echnicians stow Roman’s deployable aperture cover, a large sunshade designed to keep unwanted light out of the telescope. [NASA/Sydney Rohde] P revious page: In this photo, which peers directly down the barrel of Roman’s telescope, the photog- rapher’s camera is reflected in the primary mirror. [NASA/Sydney Rohde] tor array and confirmed it remains in proper alignment following the ob- servatory shake test. “In order to gather very sensitive measurements of objects strewn throughout space, all of Roman’s components have to be ultraprecise,” Eegholm said. “The primary mirror certainly delivers on that precision.” Roman’s primary mirror sports a layer of silver less than 400 nanometers thick — about 200 times thinner than !