The South African astronomical community together with the international SALT community recently completed a process to detail a science strategy for SALT, the 10m international telescope that SAAO operates. After six years of science operations, the telescope is a very cost-effective large telescope science producer. The strategy was adopted by the SALT Board, and has already resulted in funding choices for the next stage of instrumentation. The SALT strategy intertwines with that of the SAAO and South African optical astronomy in general. This paper outlines the process followed, the main motivations and plans for the next stage, including risks and challenges. This paper in particular concentrates on the plans to making SAAO/SALT a major player in time domain astrophysics, one of three adopted strategic science focus areas. Plans include a novel design for a high-efficiency spectrograph serving transient follow-up, for which South Africa is well positioned; advanced
software aiming to make the whole mountain-top operate as a single transient machine; feasibility studies into revolutionizing SALT observations by utilizing the primary mirror's hundreds of square degree size uncorrected field-of-view. Other SPIE papers in this meeting describe these and other developments at SALT and SAAO in more detail
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.
SpUpNIC (Spectrograph Upgrade: Newly Improved Cassegrain) is the extensively upgraded Cassegrain Spectrograph on the South African Astronomical Observatory's 74-inch (1.9-m) telescope. The inverse-Cassegrain collimator mirrors and woefully inefficient Maksutov-Cassegrain camera optics have been replaced, along with the CCD and SDSU controller. All moving mechanisms are now governed by a programmable logic controller, allowing remote configuration of the instrument via an intuitive new graphical user interface. The new collimator produces a larger beam to match the optically faster Folded-Schmidt camera design and nine surface-relief diffraction gratings offer various wavelength ranges and resolutions across the optical domain. The new camera optics (a fused silica Schmidt plate, a slotted fold flat and a spherically figured primary mirror, both Zerodur, and a fused silica field-flattener lens forming the cryostat window) reduce the camera’s central obscuration to increase the instrument throughput. The physically larger and more sensitive CCD extends the available wavelength range; weak arc lines are now detectable down to 325 nm and the red end extends beyond one micron. A rear-of-slit viewing camera has streamlined the observing process by enabling accurate target placement on the slit and facilitating telescope focus optimisation. An interactive quick-look data reduction tool further enhances the user-friendliness of SpUpNI
humidity, air pressure, wind speed and wind direction) into a database. Built upon this database, we have developed a remarkably simple approach to derive a functional weather predictor. The aim is provide up to the minute local weather predictions in order to e.g. prepare dome environment conditions ready for night time operations or plan, prioritize and update weather dependent observing queues.
In order to predict the weather for the next 24 hours, we take the current live weather readings and search the entire archive for similar conditions. Predictions are made against an averaged, subsequent 24 hours of the closest matches for the current readings. We use an Evolutionary Algorithm to optimize our formula through weighted parameters.
The accuracy of the predictor is routinely tested and tuned against the full, updated archive to account for seasonal trends and total, climate shifts. The live (updated every 5 minutes) SALT weather predictor can be viewed here: http://www.saao.ac.za/~sbp/suthweather_predict.html
PySALT is the python/PyRAF-based data reduction and analysis pipeline for the Southern African Large Telescope
(SALT), a modern 10m class telescope with a large user community consisting of 13 partner institutions. The two first
generation instruments on SALT are SALTICAM, a wide-field imager, and the Robert Stobie Spectrograph (RSS). Along
with traditional imaging and spectroscopy modes, these instruments provide a wide range of observing modes, including
Fabry-Perot imaging, polarimetric observations, and high-speed observations. Due to the large user community, resources
available, and unique observational modes of SALT, the development of reduction and analysis software is key to
maximizing the scientific return of the telescope. PySALT is developed in the Python/PyRAF environment and takes
advantage of a large library of open-source astronomical software. The goals in the development of PySALT are: (1)
Provide science quality reductions for the major operational modes of SALT, (2) Create analysis tools for the unique
modes of SALT, and (3) Create a framework for the archiving and distribution of SALT data. The data reduction software
currently provides support for the reduction and analysis of regular imaging, high-speed imaging, and long slit
spectroscopy with planned support for multi-object spectroscopy, high-speed spectroscopy, Fabry-Perot imaging, and
polarimetric data sets. We will describe the development and current status of PySALT and highlight its benefits through
early scientific results from SALT.
While time resolved astronomical observations are not new, the extension of such studies to sub-second time resolution
is and has resulted in the opening of a new observational frontier, High Time Resolution Astronomy (HTRA). HTRA
studies are well suited to objects like compact binary stars (CVs and X-ray binaries) and pulsars, while asteroseismology
of pulsating stars, occultations, transits and the study of transients, will all benefit from such HTRA studies.
HTRA has been a SALT science driver from the outset and the first-light instruments, namely the UV-VIS imager,
SALTICAM, and the multi-purpose Robert Stobie Spectrograph (RSS), both have high time resolution modes. These are
described, together with some observational examples. We also discuss the commissioning observations with the photon
counting Berkeley Visible Image Tube camera (BVIT) on SALT. Finally we describe the software tools, developed in
Python, to reduce SALT time resolved observations.
The large (~10 m) aperture of the Southern African Large Telescope (SALT) coupled with the unique capabilities
of the Robert Stobie Spectrograph (RSS), promises unparalleled prospects for polarimetric observations on an
8 - 10 m class telescope. RSS is a highly versatile first-generation instrument of the SALT. Results from
some of the first commissioning observations with the RSS are presented. A method for reducing SALT RSS
spectropolarimetry data is proposed and verified on observations of unpolarised and polarised standard stars. The
results provide estimates of telescope and instrumental polarisation as well as a calibration of the instrument's
polarimetric position angle offset.
We report on the completion of a new 2 channel, HIgh speed Photo-POlarimeter (HIPPO) for the 1.9m optical telescope of the South African Astronomical Observatory. The instrument makes use of rapidly counter-rotating (10Hz), super-achromatic half- and quarter-waveplates, a fixed Glan-Thompson beamsplitter and two photo-multiplier tubes that record the modulated O and E beams. Each modulated beam permits an independent measurement of the polarisation and therefore simultaneous 2 filter observations. All Stokes parameters are recorded every 0.1sec and photometry every 1 millisecond. Post-binning of data is possible in order to improve the signal. This is ideal for measuring e.g. the rapid variability of the optical polarisation from magnetic Cataclysmic Variable stars. First light was obtained in February 2008.