The Nancy Grace Roman Space Telescope, Explained

Telescope

Roman’s 2.4-meter primary mirror is the same diameter as Hubble’s. The telescope hardware was donated to NASA in 2012 by another federal agency and adapted for Roman’s wide-field survey work, which helped reduce the mission’s cost.

Wide Field Instrument

The heart of Roman is the Wide Field Instrument (WFI), an infrared camera with 18 HgCdTe detectors of 4096 × 4096 pixels — about 300 million pixels in all — at 0.11 arcseconds per pixel. It covers 0.28 square degrees in one exposure, roughly 45 by 23 arcminutes, and is sensitive from 0.5 to 2.3 microns.

A rotating element wheel holds eight imaging filters — F062, F087, F106, F129, F146 (wide), F158, F184 and F213 — plus a grism and a prism for slitless spectroscopy of every object in the field at once.

Coronagraph Instrument

A technology demonstration built by NASA’s Jet Propulsion Laboratory, the coronagraph uses deformable mirrors and masks to suppress starlight and directly image giant planets and dusty disks around nearby stars in visible light.

Where it works

Roman orbits the Sun–Earth L2 point about 1.5 million kilometers from Earth. It must point between 54° and 126° from the Sun, which gives it about 59 percent of the sky at any moment; stars more than 54° from the ecliptic are visible all year.

Roman, Hubble and Webb

Hubble takes sharp, detailed views of small patches of sky in ultraviolet, visible and near-infrared light. Webb’s 6.5-meter mirror reaches deeper into the infrared for extraordinary close-ups. Roman matches Hubble’s sharpness over a field about 200 times larger than Hubble’s infrared camera, so it maps vast areas quickly — finding rare objects for Hubble and Webb to study in detail.