The Nancy Grace Roman Space Telescope team has completed the calibration of its primary instrument and finalized focus adjustments. Launched on August 30, the telescope began testing its Wide Field Instrument (WFI) in September, evaluating detectors, filters, and thermal systems.
The optical performance exceeded initial requirements. While the target image quality was set at 90 nanometers RMS, the final measurement reached 63 nanometers RMS. This result represents an improvement of nearly 30 percent over the predicted values for the instrument.
To achieve this precision, engineers adjusted the secondary mirror by approximately one-sixteenth the width of a human hair. According to lead optical engineer Alden Jurling, this adjustment is proportional to moving a coin-sized distance if the mirror were scaled to the height of the Empire State Building.
The telescope's coronagraph instrument also underwent initial testing. Although it showed slight defocusing, the deviation was less than anticipated, allowing for straightforward correction. The team is now proceeding with further calibration of the coronagraph to prepare for direct exoplanet observation.
