Journal
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC
Volume 126, Issue 937, Pages 250-263Publisher
IOP PUBLISHING LTD
DOI: 10.1086/675784
Keywords
Astronomical Instrumentation
Categories
Funding
- Dunlap Institute for Astronomy and Astrophysics at University of Toronto
- NSERC [RGPIN 419376]
- Canada Foundation for Innovation [31773]
- W. M. Keck Foundation
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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 a 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 5 times less variation across the field. The new grating was installed in 2012 December, and on-sky OSIRIS throughput shows an average factor of 1.83 improvement in sensitivity between 1 and 2.4 mu m. We present the development history, testing, and implementation of this new near-infrared grating for OSIRIS and report on the comparison with the predecessors. The higher sensitivities are already having a large impact on scientific studies with OSIRIS.
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