Project Status Of The Robert Stobie Spectrograph Near Infrared Instrument (Rss-Nir) For Salt

The Robert Stobie Spectrograph Near Infrared Instrument (RSS-NIR), a prime focus facility instrument for the 11-meter Southern African Large Telescope (SALT), is well into its laboratory integration and testing phase. RSS-NIR will initially provide imaging and single or multi-object medium resolution spectroscopy in an 8 arcmin field of view at wavelengths of 0.9 - 1.7 mu m. Future modes, including tunable Fabry-Perot spectral imaging and polarimetry, have been designed in and can be easily added later. RSS-NIR will mate to the existing visible wavelength RSS-VIS via a dichroic beamsplitter, allowing simultaneous operation of the two instruments in all modes. Multi-object spectroscopy covering a wavelength range of 0.32 - 1.7 mu m on 10-meter class telescopes is a rare capability and once all the existing VIS modes are incorporated into the NIR, the combined RSS will provide observational modes that are completely unique.The VIS and NIR instruments share a common telescope focal plane, and slit mask for spectroscopic modes, and collimator optics that operate at ambient observatory temperature. Beyond the dichroic beamsplitter, RSS-NIR is enclosed in a pre-dewar box operating at -40 degrees C, and within that is a cryogenic dewar operating at 120 K housing the detector and final camera optics and filters. This semi-warm configuration with compartments at multiple operating temperatures poses a number of design and implementation challenges. In this paper we present overviews of the RSS-NIR instrument design and solutions to design challenges, measured performance of optical components, detector system optimization results, and an update on the overall project status.