Performance and results with the NIRSPEC echelle spectrograph on the Keck II Telescope

This paper describes the performance of NIRSPEC, the cryogenic cross-dispersed infrared echelle spectrograph for the Keck II telescope on Mauna Kea. NIRSPEC employs a 1024 x 1024 InSb array, diamond-machined metal optics and closed-cycle refrigeration to achieve high throughput and low backgrounds. The instrument operates directly at the f/15 Nasmyth focus, but can also be used in conjunction with the Keck adaptive optics system. First Light was obtained on April 25, 1999. As expected, the performance is detector-limited at short wavelengths and background-limited at longer wavelengths. All of the design goals have been met and results illustrating the optical performance and sensitivity are reported.