The observatory
Nancy Grace Roman Space Telescope
Roman carries a 2.4 metre mirror — the same size as Hubble's — behind a camera with roughly a hundred times the field of view. That single trade is the whole mission: it can survey in months what would take Hubble decades, at the same angular resolution, in the near-infrared where the most distant and most dust-obscured objects actually emit.
Aperture
2.4 m
Same as Hubble
Field of view
0.281 deg²
~100× Hubble's WFC3/IR
Focal plane
300.8 MP
18 H4RG detectors
Operating orbit
Sun–Earth L2
1.50M km
Observatory
Wide Field Instrument
Eighteen 4088 × 4088 infrared detectors tiled into a single focal plane
Focal plane
Optical elements
Eight imaging filters and two dispersive elements on a single wheel. Colours below follow the same convention the previews use.
| Element | Type | Pivot | Width | Coverage | Notes |
|---|---|---|---|---|---|
| F062 | imaging | 0.620 µm | 0.280 µm | Bluest imaging band; overlaps ground-based R and I. | |
| F087 | imaging | 0.869 µm | 0.217 µm | z-band analogue, used heavily for photometric redshifts. | |
| F106 | imaging | 1.060 µm | 0.265 µm | Y-band; a core High Latitude Wide Area Survey filter. | |
| F129 | imaging | 1.293 µm | 0.323 µm | J-band; a core survey filter. | |
| F146 | imaging | 1.464 µm | 1.030 µm | Very wide band for maximum depth — the microlensing workhorse. | |
| F158 | imaging | 1.577 µm | 0.394 µm | H-band; a core survey filter. | |
| F184 | imaging | 1.842 µm | 0.317 µm | Reaches past the H band for the highest-redshift sources. | |
| F213 | imaging | 2.125 µm | 0.350 µm | Reddest band; probes the most obscured and most distant objects. | |
| G150 | spectroscopy | 1.465 µm | 1.070 µm | Slitless grism, R ~ 461 — emission-line redshifts across the field. | |
| P127 | spectroscopy | 1.050 µm | 1.100 µm | Low-resolution prism for supernova classification. | |
| DARK | dark | — | — | Blocked position for dark-current and reference calibration. | |
| CGI-B1 | imaging | 0.575 µm | 0.058 µm | Coronagraph Band 1 — the primary narrow-FOV imaging demonstration. | |
| CGI-B4 | imaging | 0.825 µm | 0.083 µm | Coronagraph Band 4 — wide-field-of-view mask configuration. |
What it will observe
Most of Roman's time goes to three Core Community Surveys, designed in the open by the astronomical community rather than by a single team, with the data released publicly on arrival. The rest is guest observer time, calibration and the coronagraph demonstration.
CCS
High Latitude Wide Area Survey
Northern-cap tile covering the Extended Groth Strip, a heavily studied deep field that lets Roman's shape measurements be checked against existing high-resolution imaging.
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CCS
High Latitude Time Domain Survey
The northern time-domain pointing, close to the north ecliptic pole where the observatory's field of regard stays open year-round.
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CCS
Galactic Bulge Time Domain Survey
A second bulge pointing offset along the Galactic plane, extending the microlensing baseline into an even more crowded stellar field.
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GO
Guest Observer
A thousand-galaxy cluster at the Galactic north pole, and the field where astronomers first inferred dark matter from galaxy motions in 1933.
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CAL
Calibration
The standard photometric calibration field. Its well-characterised stars set the flux zero points that every other Roman observation is measured against.
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CGI
Coronagraph Technology Demonstration
A Sun-like star with known giant planets, used as a target to demonstrate the Coronagraph Instrument's active starlight suppression.
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