The Robert Stobie Spectrograph Near Infrared (RSS/NIR) upgrade for the Southern African Large Telescope (SALT)
extends the capabilities of the visible arm of RSS into the NIR. The RSS/NIR instrument is at the prime focus of SALT.
It is a versatile spectrograph with broadband imaging, spectropolarimetric, and Fabry-Perot imaging capabilities. The
multiple modes and prime focus location introduce interesting engineering considerations. The spectrograph has an
ambient temperature collimator, cooled (-40ºC) dispersers and camera and a cryogenic detector. Many of the
mechanisms are required to operate within the cooled and cryogenic environments. The RSS/ NIR upgrade includes the
following mechanisms; an active flexure compensating fold mirror, a filter exchange mechanism, a Volume Phase
Holographic VPH grating exchange and rotation mechanism, an etalon inserter, a beam splitter inserter, an articulating
camera, internal camera focus and a cutoff filter exchange wheel. This paper gives an overview of the mechanical design
and focuses on some of the unique testing and prototyping tasks.