Try holding a laser pointer perfectly still on a coin from 150 miles away. Impossible, surely? Yet that is roughly what NASA's Nancy Grace Roman Space Telescope has just proven it can do, floating in space rather than standing on solid ground. Between September 15 and 21, engineers at NASA's Goddard Space Flight Center in Maryland ran a punishing series of tests on Roman's fine-guidance system, the mechanism that keeps the observatory locked onto distant targets.

On September 22, the telescope's Coronagraph Instrument opened its eye to cosmic light for the very first time. The trick lies in an unusual design choice. Rather than using a separate guide camera, as other space telescopes do, Roman borrows small sections from each of the 18 detectors inside its Wide Field Instrument. Each patch watches a single guide star, whose position astronomers already know with great precision.

That data streams to the spacecraft's attitude control system nearly four times every second, allowing tiny corrective nudges that cancel out drift before it can blur an image. The results startled even the team that built the system. Roman held its position to within better than 1/100,000 of a degree, steady for 30 minutes during wide-field observations and for a remarkable eight hours during coronagraph exposures. "Our tests confirmed that we are able to keep the observatory very stable for science operations," said Begoña Vila, Roman's guiding instrument systems lead.