Atmospheric dispersion corrector for a multi-object spectroscopic mode of HROS-TMT

Abstract

Highly multiplexed spectroscopic surveys have changed the astronomy landscape in recent years. However, these surveys are limited to low and medium spectral resolution. High spectral resolution spectroscopy is often photon starved and will benefit from a large telescope aperture. Multiplexed high-resolution surveys require a wide field of view and a large aperture for a suitable large number of bright targets. This requirement introduces several practical difficulties, especially for large telescopes, such as the future ELTs. Some of the challenges are the need for a wide field atmospheric dispersion corrector and to deal with the curved non-telecentric focal plane. Here we present a concept of Multi-Object Spectroscopy (MOS) mode for TMT High-Resolution Optical Spectrograph (HROS), where we have designed an atmospheric dispersion corrector for individual objects that fit inside a fiber positioner. We present the ZEMAX design and the performance of the atmospheric dispersion corrector for all elevations accessible by TMT.