HLTDS
Roman’s High-Latitude Time-Domain Survey
Roman will revisit small patches of sky every few days to catch Type Ia supernovae — standard candles whose brightness reveals how far away they are — out to great distances.
Comparing a supernova’s distance with how much its light has been stretched by the expansion of space shows how the expansion rate has changed over billions of years. Roman’s wide field and infrared vision let it find these explosions far more efficiently than Hubble.
The adopted design includes wide and deep imaging tiers of roughly 18 and 6.5 square degrees, with slitless spectroscopy over about 4.5 and 0.5 square degrees, and cadences as short as about five days. Repeated visits will also catch other transients, from tidal disruption events to variable active galaxies.
- Imaging tiers
- ≈ 18 deg² (wide) and ≈ 6.5 deg² (deep)
- Cadence
- As short as ≈ 5 days
- Duration
- ≈ 2 years mid-mission
- Science
- Type Ia supernovae, transients
![Galactic Bulge Time-Domain Survey [figure A]](https://assets.science.nasa.gov/dynamicimage/assets/science/missions/rst/science/gbtds_figureA.png?w=480&fit=clip)
