NASA's Roman telescope completes guidance tests, receives first cosmic light

October 2, 2026 at 05:28 PM2 min

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NASA's Nancy Grace Roman Space Telescope completed fine-guidance tests from Sept. 15 to 21, demonstrating stability better than 1/100,000 of a degree for half an hour. On Sept. 22, the Coronagraph Instrument received cosmic light for the first time. The tests confirmed the observatory can remain precisely locked onto targets during long exposures.

Key Facts

Engineers tested Roman's fine-guidance system from Sept. 15 to 21, confirming stability better than 1/100,000 of a degree for half an hour at a time for Wide Field Instrument observations.
On Sept. 22, the telescope's Coronagraph Instrument received cosmic light for the first time.
Roman's Wide Field Instrument contains 18 detectors, each with a small section designated to rapidly monitor a different guide star.
The demonstrated stability is roughly comparable to keeping a laser focused on a U.S. dime from about 150 miles (240 kilometers) away.
Roman will test spectral guiding, a guidance method never used this way before, in the coming weeks.

Fine-Guidance System Tests

From Sept. 15 to 21, engineers tested Roman's fine-guidance system, which helps the observatory remain precisely locked onto its targets. The system continuously tracks reference stars and supplies information that helps the observatory correct tiny movements during an exposure. Begoña Vila, Roman's guiding instrument systems lead at NASA's Goddard Space Flight Center, said the fine-guidance system reports guide star positions about four times each second to the attitude control system. The tests confirmed stability better than 1/100,000 of a degree for half an hour at a time for Wide Field Instrument observations or for eight hours at a time for Coronagraph Instrument observations.

Coronagraph First Light

On Sept. 22, the telescope's Coronagraph Instrument received cosmic light for the first time. The Coronagraph Instrument observations require much longer exposures than Wide Field Instrument observations. Engineers expect to improve the guidance system's performance even further as they continue tuning it.

Spectral Guiding Validation

Roman will test a form of guidance that has never been used this way before. Instead of tracking only a star's point-like appearance, Roman will guide on detailed wavelength patterns called spectra. Vila said the team is looking forward to validating this spectral guiding mode in the coming weeks.