Optical design of the high-resolution near-infrared spectrograph

摘要

HRNIRS is an extremely versatile high-resolution infrared facility spectrograph designed for the Gemini South telescope. Operating over the 1.05 - 5.5 micron wavelength range, it has the capability to carry out a wide range of scientific programs by incorporating two separate modes of operation. The first is a conventional single slit cross-dispersed mode providing spectral resolution R ~ 70000 with a 0.4 arcsec slit over as much as an octave in wavelength, thus covering most of the JHK or LM windows in a single observation. In this mode the spectrograph accepts the Gemini seeing-limited f/16 input over a small field. A built-in modulator and polarizer allow HRNIRS to measure both linear and circular polarization. The second mode is a moderately-high resolution (R ~ 30000) spectrograph observing multiple objects simultaneously within a 2 arcmin field fed by the f/33.2 Gemini MCAO beam. In this paper, we discuss the optical design considerations, present the resulting design and show that the predicted performance meets the design requirements.