The Robert Stobie Spectrograph near infrared arm will provide high throughput, low to medium resolution long slit and multi-object spectroscopy with broadband, spectropolarimetric, and Fabry-Perot imaging modes over a 8′ diameter field of view. The wavelength range of the instrument is 0.9-1.7 microns, and can be operated simultaneously with the visible arm to extend the short wavelength limit to 0.32 microns. Once fielded, RSS-NIR will be the only facility instrument on an 8-10 meter class

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... scope with multi-object spectroscopy capability covering this spectral range simultaneously. RSS-NIR is scheduled to be commissioned on the 11-meter Southern African Large Telescope in late 2012. This is an upgrade to the existing visible instrument, with which it shares the slit plane and an ambient temperature collimator. Beyond the collimator, the NIR arm is cooled to -40 o C, with a cryogenic dewar containing the detector, long wavelength blocking filters, and final camera optics. This semi-warm configuration has required extensive upfront analysis of the instrumental thermal background levels, which have been incorporated into the instrument performance simulator. We present the performance predictions for spectroscopic modes of RSS-NIR and preliminary performance estimates and NIR issues still being addressed in the design for Fabry-Perot and polarimetric modes.