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Proceedings Paper

Commissioning the polarimetric modes of the Robert Stobie spectrograph on the Southern African Large Telescope
Author(s): S. B. Potter; Ken Nordsieck; Encarni Romero-Colmenero; Steve Crawford; Petri Vaisanen; Éric Depagne; David Buckley; Anthony Koeslag; Janus Brink; Christian Hetlage; Keith Browne; Lisa Crause; Alan Schier; James Allington
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Paper Abstract

The Robert Stobie Spectrograph is currently the main workhorse spectroscopic instrument on the Southern African Large Telescope (SALT), which has been undergoing regular scientific operations since 2011. The visible beam of the RSS was designed to perform polarimetry in all of its modes, imaging and grating spectroscopy (with Multi Object Spectroscopy capability) from 3200 to 9000 Å. The polarimetric field of view is 4×8 arcmin. Initial early commissioning of the polarimetric modes was stalled in 2011 because a coupling fluid leak developed in the polarizing beamsplitter after less than a year of operation. As a result, it was decided to redesign the beamsplitter to use a different optical couplant. This was complicated by the unusual thermal expansion properties of the calcite optic, and by the necessity of aligning the individual elements in the beamsplitter mosaic (RSS is the first instrument to use a mosaic beamsplitter). Laboratory work selected a new couplant: a gel, Nye 451. Testing was completed with satisfactory results on a "sacrificial" calcite prism with the same geometry as an actual mosaic element. A successful assembly was performed and the beamsplitter was re-installed in SALT in mid-2015. We describe results from the renewed commissioning efforts to characterize polarimetry from SALT and include some early performance verification science.

Paper Details

Date Published: 9 August 2016
PDF: 8 pages
Proc. SPIE 9908, Ground-based and Airborne Instrumentation for Astronomy VI, 99082K (9 August 2016); doi: 10.1117/12.2232391
Show Author Affiliations
S. B. Potter, South African Astronomical Observatory (South Africa)
Ken Nordsieck, Univ. of Wisconsin-Madison (United States)
Encarni Romero-Colmenero, South African Astronomical Observatory (South Africa)
Southern African Large Telescope
Steve Crawford, South African Astronomical Observatory (South Africa)
Southern African Large Telescope
Petri Vaisanen, South African Astronomical Observatory (South Africa)
Southern African Large Telescope
Éric Depagne, South African Astronomical Observatory (South Africa)
Southern African Large Telescope
David Buckley, South African Astronomical Observatory (South Africa)
Southern African Large Telescope
Anthony Koeslag, South African Astronomical Observatory (South Africa)
Southern African Large Telescope
Janus Brink, South African Astronomical Observatory (South Africa)
Southern African Large Telescope
Christian Hetlage, South African Astronomical Observatory (South Africa)
Southern African Large Telescope
Keith Browne, South African Astronomical Observatory (South Africa)
Southern African Large Telescope
Lisa Crause, South African Astronomical Observatory (South Africa)
Alan Schier, The Pilot Group (United States)
James Allington, The Pilot Group (United States)


Published in SPIE Proceedings Vol. 9908:
Ground-based and Airborne Instrumentation for Astronomy VI
Christopher J. Evans; Luc Simard; Hideki Takami, Editor(s)

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