Explaining the Origin of Cosmic Acceleration with the Nancy Grace Roman Space Telescope

• Cosmic acceleration is the most surprising cosmological discovery in many decades.

• Even the least exotic explanation of this phenomenon requires an energetically dominant component of the universe with properties never previously seen in nature, pervading otherwise empty space, with an energy density that is many orders of magnitude higher than naive expectations.

• Testing and distinguishing among possible explanations requires cosmological measurements of extremely high precision that probe the full history of cosmic expansion and structure growth. This program is one of the defining objectives of the Nancy Grace Roman Space Telescope (Roman), NASA next flagship astronomy mission. Roman primary mirror is 2.4 meters in diameter (7.9 feet), and is the same size as the Hubble Space Telescope’s primary mirror. Roman will have two instruments, the Wide Field Instrument, and the Coronagraph Instrument.

• The Roman mission, as described in past Science Definition Team (SDT) reports (Spergel et al. 2013a, Spergel et al. 2013b, Spergel et al. 2015), has the ability to improve these measurements by 1-2 orders of magnitude compared to the current state of the art, while simultaneously extending their redshift grasp, greatly improving control of systematic effects, and taking a unified approach to multiple probes that provide complementary physical information and cross-checks of cosmological results.

• This page describes and hosts the results of the NASA funded Science Investigation Team (SIT) dedicated to study, design and implement the cosmology program of the High Latitude Survey (HLS) that will account for about 1/3 of the mission observting time.