MARVEL: optical design for the spectrograph

MARVEL is an upcoming facility which comprises an array of four 0.8m telescopes, each feeding via fibre link into a single high-resolution echelle spectrograph. The facility is designed to provide dedicated reconnaissance and follow-up observational capability for exoplanet searches through radial velocity measurements at a precision of 1ms-1. The optical design of the MARVEL spectrograph is built around a white pupil relay with a single parabolic mirror, a prism as cross-disperser, and a purely spherical refractive camera. The spectrograph records a wavelength range of 380-950nm at spectral resolution R similar to 90,000 in a single arm with a large CCD detector. The final design has intentionally been kept simple, avoiding aspheric optics and using readily available hightransmission glasses. We present an overview of the requirements and optical design process; a brief discussion of the design avenues that were considered and decided against; and details about the expected performance of the instrument's final design.