Slitless Spectrometers for the Nancy Grace Roman Space Telescope

Primary science goals of the Roman Space Telescope include measuring the growth and geometry of the universe and developing constraints on dark energy models via complementary cosmological probes of BAO and Type Ia supernova. The Roman Space Telescope will achieve this by employing slitless spectrographs to conduct a high latitude spectroscopic survey using a near-IR grism assembly (1.0-1.93 µm, R = 435−865) and a high latitude time domain survey using a near-IR prism assembly (0.75-1.8 µm, R = 100–180). This publication covers aspects of the optical assembly designs and how the basic Roman science objectives drive the formulation and verification of the hardware’s key and driving technical performance requirements. We describe the calibration and optical metrology methods for determining assembly wavefront error, dispersion, throughput, and bandpass edge characterization. We demonstrate how the Roman Grism and Prism spectrograph designs and as-built performance meet expectations.