Spec-S5: A Next-Generation All-Sky Spectroscopic Facility Enabling Large-Scale Surveys for Cosmology and Astrophysics

Abstract

The Stage-5 Spectroscopic Experiment (Spec-S5) is a next-generation, all-sky spectroscopic facility designed to address fundamental questions in cosmology and astrophysics. Building on the legacy of the Dark Energy Spectroscopic Instrument (DESI), Spec-S5 will upgrade two existing 4-m telescopes into 6-m, wide-field observatories, each equipped with a highly multiplexed spectrograph capable of measuring 13,000 spectra simultaneously. This overview paper summarizes the science motivation, system architecture, and integration strategy of the project. Spec-S5 will deliver a more than tenfold increase in spectroscopic capability, enabling transformative surveys in the post-Rubin, post-DESI era and advancing our understanding of dark matter, dark energy, and cosmic structure formation.