Commissioning MOS and Fabry-Perot modes for the Robert Stobie Spectrograph on the Southern African Large Telescope

Type Conference Paper
Names A. R. Koeslag, T. B. Williams, K. H. Nordsieck, E. Romero-Colmenero, P. H. Vaisanen, D. S. Maartens
Conference Name Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series
Volume 9152
Pages 91520T
Date July 1, 2014
DOI 10.1117/12.2055732
ISBN 0277-786X
Library Catalog
Abstract The Southern African Large Telescope (SALT) currently has three instruments: the imaging SALTICAM, the new High Resolution Spectrograph (HRS) which is in the process of being commissioned and the Robert Stobie Spectrograph (RSS). RSS has multiple science modes, of which long slit spectroscopy was originally commissioned; We have commissioned two new science modes: Multi Object Spectroscopy (MOS) and Fabry-Perot (FP). Due to the short track times available on SALT it is vital that acquisition is as efficient as possible. This paper will discuss how we implemented these modes in software and some of the challenges we had to overcome. MOS requires a slit-mask to be aligned with a number of stars. This is done in two phases: in MOS calibration the positions of the slits are detected using a through-slit image and RA/DEC database information, and in MOS acquisition the detector sends commands to the telescope control system (TCS) in an iterative and interactive fashion for fine mask/detector alignment to get the desired targets on the slits. There were several challenges involved with this system, and the user interface evolved to make the process as efficient as possible. We also had to overcome problems with the manufacturing process of the slit-masks. FP requires the precise alignment each of the two etalons installed on RSS. The software makes use of calibration tables to get the etalons into roughly aligned starting positions. An exposure is then done using a calibration arc lamp, producing a ring pattern. Measurement of the rings allows the determination of the adjustments needed to properly align the etalons. The software has been developed to optimize this process, along with software tools that allow us to fine tune the calibration tables. The software architecture allows the complexity of automating the FP calibration and procedures to be easily managed.
UW-Madison Astronomy Home