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arXiv · 1401.4456

Efficiency Measurements and Installation of a New Grating for the OSIRIS Spectrograph at Keck Observatory

Etsuko Mieda·Shelley A. Wright·James E. Larkin·James R. Graham·Sean M. Adkins·James E. Lyke·Randy D. Campbell·Jerome Maire·Tuan Do·Jacob Gordon
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Abstract

OSIRIS is a near-infrared integral field spectrograph operating behind the adaptive optics system at W. M. Keck Observatory. While OSIRIS has been a scientifically productive instrument to date, its sensitivity has been limited by a grating efficiency that is less than half of what was expected. The spatially averaged efficiency of the old grating, weighted by error, is measured to be 39.5 +/- 0.8 % at {\lambda} = 1.310 {\mu}m, with large field dependent variation of 11.7 % due to efficiency variation across the grating surface. Working with a new vendor, we developed a more efficient and uniform grating with a weighted average efficiency at {\lambda} = 1.310 {\mu}m of 78.0 +/- 1.6 %, with field variation of only 2.2 %. This is close to double the average efficiency and five times less variation across the field. The new grating was installed in December 2012, and on- sky OSIRIS throughput shows an average factor of 1.83 improvement in sensitivity between 1 and 2.4 microns. We present the development history, testing, and implementation of this new near-infrared grating for OSIRIS and report the comparison with the predecessors. The higher sensitivities are already having a large impact on scientific studies with OSIRIS.

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Etsuko Mieda, Shelley A. Wright, James E. Larkin, James R. Graham, Sean M. Adkins, James E. Lyke, Randy D. Campbell, Jerome Maire, Tuan Do, Jacob Gordon. 2014-01-17. Efficiency Measurements and Installation of a New Grating for the OSIRIS Spectrograph at Keck Observatory. https://doi.org/10.1086/675784

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