The NIR upgrade to the SALT Robert Stobie Spectrograph

The near infrared (NIR) upgrade to the Robert Stobie Spectrograph (RSS) on the Southern African Large Telescope (SALT), RSS/NIR, extends the spectral coverage of all modes of the visible arm. The RSS/NIR is a low to medium resolution spectrograph with broadband imaging, spectropolarimetric, and Fabry-Perot imaging capabilities. The visible and NIR arms can be used simultaneously to extend spectral coverage from approximately 3200 Å to 1.6 μm. Both arms utilize high efficiency volume phase holographic gratings via articulating gratings and cameras. The NIR camera is designed around a 2048x2048 HAWAII-2RG detector housed in a cryogenic dewar. The Epps optical design of the camera consists of 6 spherical elements, providing sub-pixel rms image sizes of 7.5 ± 1.0 μm over all wavelengths and field angles. The exact long wavelength cutoff is yet to be determined in a detailed thermal analysis and will depend on the semi-warm instrument cooling scheme. Initial estimates place instrument limiting magnitudes at J = 23.4 and H(1.4-1.6 μm) = 21.6 for S/N = 3 in a 1 hour exposure well below the sky noise.

[1]  Michael P. Smith,et al.  Prime Focus Imaging Spectrograph for the Southern African Large Telescope: optical design , 2003, SPIE Astronomical Telescopes + Instrumentation.

[2]  David A. H. Buckley,et al.  Southern African Large Telescope (SALT) project: progress and status after 2 years , 2003, SPIE Astronomical Telescopes + Instrumentation.

[3]  David A. H. Buckley,et al.  Southern African Large Telescope (SALT) project progress and status after four years , 2004, SPIE Astronomical Telescopes + Instrumentation.

[4]  Jian Swiegers,et al.  The optical design of the Southern African Large Telescope , 2003, SPIE Astronomical Telescopes + Instrumentation.

[5]  Michael P. Smith,et al.  Prime focus imaging spectrograph for the Southern African large telescope: operational modes , 2003, SPIE Astronomical Telescopes + Instrumentation.

[6]  Darragh O'Donoghue,et al.  Science drivers and first generation instrumentation for the Southern African Large Telescope (SALT) , 2003, SPIE Astronomical Telescopes + Instrumentation.