Optical design options for Pollux: UV spectropolarimeter project for the Habitable Worlds Observatory

Pollux is a project of UV spectropolarimeter proposed as a European contribution for the planned NASA-led Habitable Worlds Observatory. It comprises of four channels. Three of them are operating in the near-UV, medium UV, and visible range, each representing an echelle spectrograph with a birefringent polarimeter. It is possible to reach the resolving power of R130 000 with the maximum throughput of ~11% in the near UV (236-472 nm) and R95 000 with ≤5% transmission in the medium UV (118-236 nm). A fourth channel for the far-UV below Lyman-alpha is studied with a different design. Finally, we provide an overview of the key science goals and the technological risks.