Commissioning of the Southern African Large Telescopes (SALT) first-generation instruments

The Southern African Large Telescope is nearing the end of its commissioning phase and scientific performance verification programmes began in 2006 with two of its First Generation UV-visible instruments, the imaging camera, SALTICAM, and the multi-mode Robert Stobie Spectrograph (RSS). Both instruments are seeing limited and designed to operate in the UV-visible region (320 - 900 nm). This paper reviews the innovative aspects of the designs of these instruments and discusses the commissioning experience to date, illustrated by some initial scientific commissioning results. These include long-slit and multi-object spectroscopy, spectropolarimetry, Fabry-Perot imaging spectroscopy and high-speed photometry. Early spectroscopic commissioning results uncovered a serious underperformance in the throughput of RSS, particularly at wavelengths < 400nm. We discuss the lengthy diagnosis and eventual removal of this problem, which was traced to a material incompatibility issue involving index-matching optical coupling fluid. Finally, we briefly discuss the present status of the third and final First Generation instrument, a vacuum enclosed fibre-fed high resolution, dual beam, white pupil echelle spectrograph, SALT HRS, currently under construction.