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

This paper describes the performance of NIRSPEC, the cryogenic cross-dispersed IR echelle spectrograph for the Keck II telescope on Mauna Kea. NIRSPEC employs a 1024 by 1024 InSb array, diamond-machined metal optics and closed- cycle refrigeration on 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 result illustrating the optical performance and sensitivity are reported.