GREENBELT, Oct. 15 -- Engineers moved the secondary mirror of NASA's Nancy Grace Roman Space Telescope by about one-sixteenth the width of a human hair, and the observatory's main camera now produces sharper images than the agency's own models predicted.

The optics of the Wide Field Instrument now show an error of 63 nanometers RMS, NASA said, against a requirement of about 90, which the agency describes as nearly 30% better than the team predicted. The telescope launched August 30 aboard a SpaceX Falcon Heavy, and the instrument was switched on in September.

That matters because every one of Roman's sweeping surveys runs through it. "Many of the mission's primary goals, like studying dark matter and dark energy, wouldn't be possible wi...