Abstract

The Nancy Grace Roman Space Telescope is the next NASA Astrophysics flagship mission scheduled to launch no later than May 2027.  Roman’s Galactic Bulge Time Domain Survey (GBTDS) will provide an unprecedented census of extrasolar cold and free-floating planets detected via gravitational microlensing of background stars.  The notional survey design involves seven fields (with a total area ~2 sq. degrees) monitored by Roman’s Wide Field Instrument continuously every 15 minutes during six 72-day bulge seasons when the Galactic bulge is visible from Roman.  This survey will also enable a broad range of auxiliary science, including the measurement of the compact object mass function over ten orders of magnitude, the detection of 100,000 Transiting Planets, astroseismology of 1,000,000 bulge giants, the detection of 5000 trans-Neptunian objects, and the measurement of parallaxes and proper motions of 6,000,000 bulge and disk stars.  Although the parameters of the GBTDS needed to achieve Roman’s core science requirement are relatively tightly constrained, some alterations and/or augmentation may result in significant additional science without sacrificing these requirements.