Roman's focus is sharper than planned
The full reading behind my Short: NASA's newest space telescope needed only a tiny nudge, and its main camera is now sharper than the team predicted.
The short version
NASA's Nancy Grace Roman Space Telescope, which launched on 30 August 2026, has finished checking out its main instrument and fine-tuning its focus [1]. After corrections, the Wide Field Instrument's optics have an error of just 63 nanometres RMS, against a requirement of about 90 nanometres RMS. NASA says its performance is nearly 30% better than the team predicted [1].
A tiny nudge
Ground testing could not exactly reproduce space: there is no gravity, and temperature and moisture differ slightly [1]. But the optics arrived almost perfectly aligned, so the team only made minuscule adjustments [1].
Senior optical engineer Alden Jurling: "We moved the secondary mirror by about one-sixteenth of the diameter of a human hair." Scaled up to the Empire State Building, that is a little less than stacking a single US penny on the tip of the tower [1].
Watch the Short
About this page
The Short uses NASA public-domain images of Roman, its primary mirror and its Wide Field Instrument, plus my own simple animations (galaxy, hair cross-section, building and bar chart), which are illustrations and not to scale. This page is general science news.
Why it matters
- Sharper surveys. "All of Roman's sweeping surveys will rely on the Wide Field Instrument," says systems engineer Dave Hickey; goals like studying dark matter and dark energy depend on it [1].
- What RMS means. The ~90 nm requirement means the optics may deviate from perfection by about 90 nanometres, around 1,000 times thinner than a human hair. Roman now sits at 63 nm [1].
- Coronagraph. The Coronagraph Instrument's images were slightly out of focus at first (less than expected) and now meet the team's high expectations; light-blocking demonstrations are planned in the coming weeks [1].
- Still commissioning. These are checkout results; science surveys come after commissioning [1].
Full narration (transcript)
NASA just sharpened the focus of its newest space telescope, and it's better than planned. Roman launched on August 30th, to help study dark matter and dark energy. Good focus matters, because all of Roman's sweeping surveys rely on its Wide Field Instrument. Before launch, its optics were aligned on the ground, but space can shift things. In space, the team only needed tiny adjustments. The team moved its secondary mirror by about a human hair's width, divided by sixteen. Imagine the Empire State Building. The change is less than one penny on top. Roman's Coronagraph Instrument was slightly out of focus at first, and it now meets the team's high expectations. Its main camera, the Wide Field Instrument, had an image quality requirement of about 90 nanometres. Today, after the corrections, its optics are off from perfection by just sixty-three nanometres. NASA says that beats the team's prediction by close to 30 percent.
Sources
- [1] NASA (14 Oct 2026). "NASA Roman Team Checks Out Main Instrument, Sharpens Telescope's Focus." science.nasa.gov
- [2] Images: NASA, public domain, via Wikimedia Commons: Roman illustration · primary mirror · Wide Field Instrument · Roman in space
Credits
Images: NASA (public domain). Animations: my own illustrations. Not endorsed by NASA.