OSIRIS at the W. M. Keck Observatory

We present the results of the upgrade of the spectrograph detector in the integral eld spectrograph, OSIRIS. OSIRIS is a near-infrared (1 to 2.5 microns) integral eld spectrograph on the Keck I telescope. This instrument produces up to 3,000 spectra simultaneously over a contiguous rectangular eld of view with a spectral resolution of 3,800. OSIRIS works with the Keck Adaptive Optics system to achieve diraction-limite d spatial resolution and has four plate scales ranging from 0.02 to 0.10 arcseconds. At rst light in 2005, the spectrograph portion of the instrument was equipped with a Rockwell Hawaii-2 detector. We have now upgraded this to a Teledyne Hawaii-2RG (H2RG) with lower read noise, lower dark current, and higher quantum eciency. In addition to the upgraded detector, we also mounted the detector head on a linear stage, allowing the position of the detector to be accurately adjusted along the optical path when the instrument is at cryogenic temperatures (80 K). This reduced the number of cool downs required to put the detector image plane at the spectrograph camera focus and adjust any residual tip/tilt of the detector image plane. We present the results of commissioning the new detector and the improved sensitivities of the OSIRIS instrument due to this upgrade.