Most space telescopes work like a spotlight: point at one target and study it closely. NASA's Nancy Grace Roman Space Telescope is built more like a surveyor's camera. It launched on August 30, 2026, and NASA expects its first science images by early 2027.
If you like systems that sample the world at different resolutions and rates, Roman is a fun design to read about.
Same mirror as Hubble, a much bigger window
Roman's main mirror is 2.4 m across, the same as Hubble's. Its Wide Field Instrument takes images as sharp as Hubble's over a field of view at least 100 times larger (0.28 square degrees).
Hubble shows one street corner in fine detail. Roman shows the whole neighborhood at the same detail.
Survey 1: a map with three zoom levels
The High-Latitude Wide-Area Survey has three tiers, like a road atlas, a city map and a street view:
| Tier | Area | What it is for |
|---|---|---|
| Wide | 2,700 sq. degrees, one filter | the "road atlas" |
| Medium | 2,400 sq. degrees, three filters, images and spectra | the "city map" |
| Deep | 19.2 sq. degrees, about 1.2 magnitudes deeper | the "street view" |
The goal is to study cosmic acceleration with weak gravitational lensing and the way galaxies cluster.
Survey 2: the same sky, again and again
The High-Latitude Time-Domain Survey revisits the same fields to catch things that change, mainly Type Ia supernovae, which are used to measure how the universe expanded. The northern and southern fields are each visited about every 5 days, and some filters repeat every 10 days. It is a time series, observed at a fixed cadence.
Survey 3: planets from bent space
The Galactic Bulge Time-Domain Survey watches the crowded centre of the Milky Way. It uses microlensing: when a star passes in front of a more distant one, its gravity bends the light like a natural magnifying glass. NASA expects it to find more than a thousand wide-orbit planets, plus free-floating planets that orbit no star. In its high-cadence seasons it samples every 12 minutes.
A test for finding Earth-like worlds
Roman also carries a Coronagraph, a technology demonstration that blocks a star's glare so fainter things next to it can be seen. Its deformable mirrors have more than 1,600 actuators, each commanded to better than 62 picometers.
What we do not know yet
NASA's recent updates do not say when the surveys will begin or how many supernovae it wany number you read elsewhere. My full article lists the sources, with a link for everyclaim:
Read the full article on Leo's Station
Image credit: NASA.
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