The Galactic Bulge Time Domain Survey (GBTDS) is one of the three CCS to be executed by the Nancy Grace Roman Space Telescope. The primary science driver for the Roman GBTDS, and high priority goal for the field (as captured in the Astro2010 Decadal Report) is the demographics of cold exoplanets. This science will be enabled by obtaining high cadence (∼12 minute), high precision time series photometry using Roman's Wide Field Instrument (WFI) over a nominal ∼2-square degree field of view towards the Galactic bulge, in order to observe microlensing events caused by both bound and free-floating planets. The ROTAC recommended the overguide survey from the CCS definition committee interim report, which will cover 5 contiguous fields, plus an additional field covering the Galactic Center, with two important modifications: the first high-cadence Bulge season be modestly reduced to leave time for the Galactic Plane Survey, and that the Roman observing schedule during the low-cadence seasons be further studied to minimize disruption to the HLTDS and GAS. The survey will have a total duration of 440 days spread over the 5-year prime mission. The yield of bound planets should be 13.1 and 142.2 for 0.1 M⊕ and 1 M⊕, respectively, and of free-floating planets, 8.7 and 38.4 for 0.1 M⊕ and 1 M⊕, respectively.
| Survey Component |
Nominal Survey |
|---|---|
| Number of high-cadence seasons | 6 |
| Observing allocation per season (days) | 70.5 |
| Feasible season length (days) | 72 |
| Number of contiguous fields | 5 |
| Observing cadence (min) | 12.1 |
| Exposure time (sec) | 66.9 |
| Number of low-cadence seasons | 4 |
| Observing cadence (days) | 3 |
| Number of photometry snapshots | 30 |
| Number of grism snapshots | 30 |
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