The New SDSS 2.5 m Telescope Wide-field Corrector for SDSS-V

Abstract SDSS-V is the fifth generation of the Sloan Digital Sky Survey and is an ambitious follow-up to a project that has been producing ground-breaking science for more than two decades. SDSS-V uses two dedicated 2.5 m telescopes—the SDSS telescope at Apache Point Observatory in New Mexico and the du Pont telescope at Las Campanas Observatory in Chile—feeding the BOSS and APOGEE spectrographs at each site. These survey machines generate multiobject, all-sky spectroscopy in the optical and near-infrared in support of primary science programs. The new wide-field corrector for the SDSS 2.5 m telescope is one of several major infrastructure upgrades undertaken for SDSS-V, necessitated by the replacement of the legacy fiber plug plate system with a new robotic Focal Plane System (FPS), which places different requirements on the focal characteristics of the telescope. The original two-element corrector produced a focal surface that was nontelecentric and suffered from axial color, throughput, and image quality issues when used in the H band with the APOGEE spectrograph. We have designed and built a three-element fused silica corrector that addresses the optical shortcomings in relation to the FPS. This paper discusses the optical and optomechanical design details of the new wide-field corrector, provides a detailed description of the assembly, integration, and test effort, and concludes with a description of the commissioning effort and on-sky performance.