Telescope for NASA’s Roman mission complete and delivered to Goddard

18 Nov 2024

Grace Roman Space Telescope “one giant step” closer to unlocking the mysteries of universe.

Optical telescope assembly for the Nancy Grace Roman Space Telescope.

NASA’s Nancy Grace Roman Space Telescope is one giant step closer to unlocking the mysteries of the universe. The mission has now received its final major delivery: the Optical Telescope Assembly, which includes a 2.4-meter (7.9-foot) primary mirror, nine additional mirrors, and supporting structures and electronics. The assembly was delivered November 7th to the largest clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, where the observatory is being built.

The telescope will focus cosmic light and send it to Roman’s instruments, revealing many billions of objects strewn throughout space and time. Using the mission's Wide Field Instrument, a 300-megapixel infrared camera, astronomers will survey the cosmos from the outskirts of our solar system toward the edge of the observable universe. Scientists will use Roman’s Coronagraph Instrument to test new technologies for dimming host stars to image planets and dusty disks around them in far better detail than ever before.

“We have a top-notch telescope that is well aligned and has great optical performance at the cold temperatures in space,” said Bente Eegholm, optics lead for Roman’s Optical Telescope Assembly at NASA Goddard. “I am looking forward to the next phase where the telescope and instruments will be put together to form the Roman observatory.”

Polishing the mirror

Designed and built by L3Harris Technologies, Rochester, NY, the assembly incorporates key optics including the primary mirror that were made available to NASA by the U.S. National Reconnaissance Office. The team at L3Harris then reshaped the mirror and built upon the inherited hardware to ensure it would meet Roman’s specifications for expansive, sensitive infrared observations.

“The telescope will be the foundation of all of the science Roman will do, so its design and performance are among the largest factors in the mission’s survey capability,” said Josh Abel, lead Optical Telescope Assembly systems engineer at NASA Goddard. The team at Goddard worked closely with L3Harris to ensure these stringent requirements were met and that the telescope assembly will integrate smoothly into the rest of the Roman observatory.

The assembly's design and performance will largely determine the quality of the mission's results, so the manufacturing and testing processes were extremely rigorous. Each optical component was tested individually prior to being assembled and assessed together earlier this year. The tests helped ensure that the alignment of the telescope’s mirrors will change as expected when the telescope reaches its operating temperature in space.

Then, the telescope was put through tests simulating the extreme shaking and intense sound waves associated with launch. Engineers also made sure that tiny components called actuators, which will adjust some of the mirrors in space, move as predicted. The team measured gases released from the assembly as it transitioned from normal air pressure to a vacuum—the same phenomenon that has led astronauts to report that space smells gunpowdery or metallic. If not carefully controlled, these gases could contaminate the telescope or instruments.

Finally, the telescope underwent a month-long thermal vacuum test to ensure it will withstand the temperature and pressure environment of space. The team closely monitored it during cold operating conditions to ensure the telescope’s temperature will remain constant to within a fraction of a degree. Holding the temperature constant allows the telescope to remain in stable focus, making Roman’s high-resolution images consistently sharp. Nearly 100 heaters on the telescope will help keep all parts of it at a stable temperature.

“It is difficult to design and build a system to hold temperatures to such a tight stability, and the telescope performed exceptionally,” said Christine Cottingham, thermal lead for Roman’s Optical Telescope Assembly at NASA Goddard. Now that the assembly has arrived at Goddard, it will be installed onto Roman’s Instrument Carrier, a structure that will keep the telescope and Roman’s two instruments optically aligned. The assembly's electronics box—essentially the telescope's brain—will be mounted within the spacecraft along with Roman’s other electronics. With this milestone, Roman remains on track for launch by May 2027.