The Wide-Field Spectroscopic Telescope (WST)

We propose a conceptual design study for a 12-metre wide-field spectroscopic survey telescope (WST) with simultaneous operation of a large field-of-view (3 sq. degree), high-multiplex (20,000) multiobject spectrograph (MOS) and a giant 3x3 arcmin integral field spectrograph (IFS). In scientific capability these specifications place WST far ahead of existing and planned facilities. In only 5 years of operation, the MOS would target 250 million galaxies and 25 million stars at low spectral resolution plus 2 million stars at high resolution. Without need for pre-imaged targets, the IFS would deliver 4 billion spectra offering many serendipitous discoveries. Given the current investment in deep imaging
surveys and noting the diagnostic power of spectroscopy, WST will fill a crucial gap in astronomical capability and work in synergy with future ground and space-based facilities. We show how it can
address outstanding scientific questions in the areas of cosmology; galaxy assembly, evolution, and enrichment, including our own Milky Way; the origin of stars and planets; and time domain and multimessenger astrophysics. WST’s uniquely rich dataset may yield unforeseen discoveries in many of these areas. The study will deliver telescope and instrument designs, cost estimates, an updated science white paper and survey plan, concept studies for data management, and a facility operation concept. The telescope and instruments will be designed as an integrated system and will mostly use existing technology, with the aim to minimise the carbon footprint and environmental impact. We will propose WST as the next ESO project after completion of the 39-metre ELT. Our consortium includes institutes
from Australia, which has a strategic partnership with ESO and aims to apply shortly for full
membership. Together with ESO and institutes in 9 European countries, our team has the necessary technical and scientific expertise, and brings 70 years of in-kind effort to the proposed study.

In Vienna, we will focus on the minimisation of the environmental impact of facility
construction and that the site selection and construction will be undertaken in a sustainable
manner. We will also ensure that operations are run sustainably. This includes operations at the telescope, but also the impact of data processing, management, and storage. The carbon footprint for both the construction and operation of WST will be documented at the end of the study. It will build on best practices from other similar current and planned projects.