NASA's Nancy Grace Roman Space Telescope: Final Assembly Update
This video, covering the second half of 2025, shows the Goddard Space Flight Center’s largest clean room, the Spacecraft Systems Development and Integration Facility in Greenbelt, Maryland. The room is a class 10,000 clean room with over one million cubic feet of space.
The outside half of NASA's Nancy Grace Roman Space Telescope, called OSD, contains the solar panels & protective layers. The Deployable Aperture Cover protects the mirrors during launch and then unfolds to help shield them from sunlight does a test deployment. During this test, lines connect to it and pull upward to negate Earth’s gravitational forces. Of course, Roman will not experience this in space. Then, the Solar Array Sun Shield panels deploy. There are four panels that move. They fold against the spacecraft to fit in the rocket fairing and deploy in space to make a large flat plane that collects light to generate electricity and helps keep the rest of Roman cool.
In preparation for additional testing, technicians put a clean tent over OSD and transport it out of the clean room. They push it into the acoustic test chamber where a six-foot-tall horn projects up to 150-decibel sound at varying frequencies. The other tests are on two vibration tables that shake Roman along all three axes: up/down, left/right & forward/backward. Engineers attach hundreds of sensors and run tests of increasing intensity. During and after each test, they carefully study the data to make sure that Roman is reacting as expected.
While these tests occur, Roman’s inside half, containing the mirrors, instruments & support equipment, move into Goddard’s largest thermal vacuum chamber, the Space Environment Simulator (SES). This 40-foot-tall chamber can simulate the vacuum of space & the wide temperature range that Roman will experience there: from -310° F (-190° C) to 302° F (150° C). The move to the chamber happens without a clean tent, so the entire path was cleaned, and all the workers dress in full clean-room garb to ensure that no dirt contaminates the sensitive parts of the spacecraft. Once the two layers of doors are sealed, Roman spends 72 days inside running through tests at various temperatures and with equipment turned on to ensure that it works at low temperature in a vacuum. A special array installed above the mirror projects light that engineers use to test the optics and sensors.
After leaving the SES chamber and returning to the SSDIF, Roman’s primary and secondary mirrors are carefully cleaned and inspected. It is a balance to get the mirrors as clean as possible while not cleaning too aggressively and damaging the delicate surfaces. The mirrors are cleaned horizontally with a gentle vacuum cleaner and vertically with brushes. After this cleaning, every inch is visually inspected and photographed to record the exact optical characteristics. This was the last time the primary mirror would be accessible.
Finally, in late November, Roman’s two halves are joined together to form the complete observatory. The process takes the better part of a day. Two guide poles are installed on the inside half to help direct OSD down onto it. At various times, the clearances between the two halves are only a few inches. With the observatory complete, it begins preparing for another round of deployments and testing.
On track to launch in fall 2026, the Roman Space Telescope is NASA’s next flagship astrophysics mission. An infrared survey telescope with the same resolution as Hubble but at least 100 times the field of view, Roman is being built and tested at NASA Goddard. Partners worldwide are contributing to this effort.
0:00 - Roman in the Clean Room
0:14 - Deployment Tests
0:33 - Acoustic and Vibration Tests
1:05 - Thermal Vacuum Testing
1:40 - Mirror Cleaning
1:56 - Joining the Halves
Credit: NASA’s Goddard Space Flight Center
Producer: Scott Wiessinger (eMITS)
Videographers (eMITS): Sophia Roberts, Scott Wiessinger, Rob Andreoli, John Philyaw
Editor: Scott Wiessinger (eMITS)
Science Writer: Ashley Balzer (eMITS)
Duration: 2 minutes, 29 seconds
Release Date: March 19, 2026
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