NASA’s Nancy Grace Roman Space Telescope is steadily waking up on its three‑month cruise to the Sun–Earth L2 Lagrange point. About a million miles from Earth, L2 lets Roman stay on the night side of our planet with the Sun behind it — ideal conditions for its two primary instruments: the Wide Field Instrument (WFI) and the Coronagraph Instrument.
Wide Field Instrument: 300‑megapixel infrared surveyor
The WFI is a 300‑megapixel infrared camera built to map huge portions of the sky. It uses 18 infrared detectors with a combined sensing area roughly the size of a laptop screen; by comparison, a typical digital camera sensor is about the size of a postage stamp. With this system, scientists aim to:
- take rapid, wide‑field snapshots of the cosmos,
- probe dark energy,
- map the large‑scale distribution of matter in the universe.
Before powering up WFI, engineers let the instrument dry out for about 10 days at roughly ‑85°F (‑65°C) to drive off contaminants from pre‑launch operations. On Sept. 11 they switched off its heater, allowing it to cool to about ‑225°F (‑143°C) — cold enough to safely activate the infrared detectors. The sensors are now being cooled further toward their ~‑300°F (‑183°C) operating temperature.
After detector activation, the team calibrated the WFI element wheel, which selects different wavelengths using filters, prisms and other optics, and confirmed on Sept. 13 that the focus mechanisms are working nominally.
Coronagraph: turning off starlight to see exoplanets
Roman’s coronagraph is controlled from the Coronagraph Commanding Center at Caltech/IPAC in Pasadena. Initial tests verified remote operation of its electronic and mechanical subsystems. The instrument uses mirrors, masks and sensors to block a star’s light so it can detect the far fainter glow of planets in orbit around that star.
For ground‑like testing, engineers warmed the coronagraph to 72°F (22°C) — typical for Earth‑based clean rooms but much warmer than WFI’s cryogenic regime. This allows conditions similar to NASA test chambers, making it easier to simulate and tune deformable mirrors. Afterward, the team began a decontamination phase, holding the detectors warm so that water and trace chemicals can outgas from their surfaces.
Early downlinks from Roman show nominal performance, marking an important milestone on the way to full science operations.
Source: Space.com
