Performance modeling of an upgraded NIRSPEC on Keck

NIRSPEC is a high-resolution near-infrared (1-5 micron) echelle spectrometer in use on the Keck II telescope. We are designing an upgrade to the spectrometer, and here we present modeling for the expected performance of the upgraded system. The planned upgrade will (1) replace the Aladdin III science detector with a Teledyne H2RG, (2) update the slitviewing camera (SCAM) detector to an H1RG and replace the optics, and (3) upgrade the instrument control electronics. The new spectrometer detector has smaller pixels but a larger format, and its improved noise characteristics will provide a dramatic increase in sensitivity, especially between OH lines in H-band and shorter wavelengths. Optical modeling shows that the upgraded system is expected to achieve higher spectral resolution and a larger spectral grasp. Also, preliminary modeling of the SCAM optical design aims to permit operation from 1-5 μm, overcoming a limitation with the existing system.