Optical design of a multi-object fiber-fed spectrograph system for Southern Spectroscopic Survey Telescope

TL;DR

This paper presents an optical design for a multi-object fiber-fed spectrograph for the Southern Spectroscopic Survey Telescope, emphasizing high imaging quality and transmittance using Volume Phase Holographic Gratings.

Contribution

It introduces a detailed design methodology for MOFFS systems based on VPHGs, including optimization procedures and analytic methods.

Findings

High imaging quality achieved in the final design

Relatively high transmittance across the waveband

Design approach applicable to similar telescopes

Abstract

Southern Spectroscopic Survey Telescope (SSST) is a wide-field spectroscopic survey telescope that China plans to build in Chile in the next few years. As an instrument for astronomical spectroscopic survey, the multi-object and fiber-fed spectrograph (MOFFS) is one of the most important scientific instruments for SSST. In this paper, we present a recommended optical design for the MOFFS system based on the Volume Phase Holographic Gratings (VPHG). The whole design philosophy and procedure, including the analytic method to determine the initial structure, optimization procedures of the VPHG and the camera groups, are demonstrated in detail. The numerical results of the final obtained spectrograph show a superior imaging quality and a relatively high transmittance for the whole working waveband and the field of view. The design method proposed in this paper can provide a reference for the design of MOFFS accommodated in spectroscopic survey telescopes.