Telescope Overview & Status:
The SOAR Telescope is designed to carry a large instrument payload. An Instrument Support Box (ISB) at each Nasmyth focus can carry a cluster of three instruments and contains a shared Tip-Tilt guider and calibration unit. Two "Folded Cassegrain" ports on the elevation ring can each support an additional smaller instrument. A third “Folded Cassegrain” port holds the Calibration Wavefront Sensor (CWFS) used to tune the Active Optical System (AOS). The system is designed to allow the observer to switch between instruments, several of which can be “science ready” at any time, within a few minutes. The tertiary mirror rotates to select the focal station in use while beam steering optics within each ISB direct the light to the chosen instrument.
The SOAR AOS uses 120 movable axial supports to maintain the figure of the primary mirror and 6 lateral supports that take up the weight of the M1 as the telescope elevation changes. The CWFS is used to measure the wave front delivered by the telescope and adjust the forces applied to the axial supports, allowing us to produce seeing limited images with SOAR. The tertiary mirror is equipped with a tip-tilt control unit and can be used at up to 50Hz to improve the seeing for all mounted instruments.
Instruments in Science Use:
SOAR Optical Imager (SOI) - The SOI is a mosaicked imager with two EEV 2x4k CCDs and has a FoV of 5.5’ square with 77mas pixels. The SOI optics were selected to ensure high transmission over the entire 320-1050nm passband.
SOI is equipped with two filter wheels that have space for four filters, plus one clear position, so that up to eight filters can be installed in the instrument at any time. Filters may be up to 100mm square and 10mm thick. Smaller filters may be accommodated using special adapters but must be at least 64mm square to avoid vignetting.
Ohio State Infra-Red Imager/Spectrometer (OSIRIS): - OSIRIS is a multi-purpose infrared imager & spectrometer built by the Ohio State University and is deployed at SOAR 4.1m as a facility IR instrument. OSIRIS operates at wavelengths from 0.9 to 2.4 microns and uses a 1024x1024 HAWAII HgCdTe array supplied by CTIO. OSIRIS contains two reimaging cameras, f2.8 and f7.
In imaging mode at SOAR, the f2.8 camera has a plate scale of 0.331”/pixel and a FOV of 191”. The f7 camera has a plate scale of 0.139”/pixel and a FOV of 80”.
OSIRIS has three spectroscopic modes: Low-Res, High-Res, and Cross-Dispersed. Some values for these spectroscopic modes are given below.
Goodman High Throughput Spectrograph (Goodman) – The Goodman imaging spectrograph was built at the Goodman Laboratory at the University of North Carolina at Chapel Hill. Goodman employs all transmissive optics, and Volume Phase Holographic (VPH) Gratings to achieve the highest possible throughput for low and moderate resolution spectroscopy over the 320-900 nm wavelength range and uses a Fairchild 4k × 4k detector with 150mas pixels.
Instruments in Science Use (Cont):
Goodman High Throughput Spectrograph (Goodman)
In imaging mode, Goodman has a plate scale of 0.15”/pixel and the FOV is 7.2’ in diameter (3096 × 3096) pixels. Goodman contains two independent, six position filter wheels that hold 4” diameter filters. The imaging filters are comprised of a UBVR filter set on the Kron-Cousins system.
In spectroscopic mode, Goodman is currently deployed with seven fixed long-slit masks with widths of 0.46, 0.84, 1.03, 1.35, 1.68, 3.0, and 10.0 arcsec. Goodman is used with any of five (400l/mm, 600l/mm/, 930l/mm, 1200l/mm, and 2100l/mm) VPH gratings and features an articulated camera that allows the camera/grating angles to be adjusted to tune the blaze angle, maximizing the efficiency at any desired wavelength.
Spartan High-Resolution Infrared Camera (Spartan) - The Spartan HIRC is a high spatial-resolution near-IR imager built at Michigan State University and has a focal plane that consists of four “Hawaii-II” 2048×2048 HgCdTe detector arrays.
Spartan operates in the 1.0-2.4 micron band for imaging with tip-tilt correction. Spartan has two focal ratios, an f/12 wide-field imaging mode with 0.068”/pixel and an f/21 high-resolution imaging mode with 0.040”/pixel. In the wide-field imaging mode, the Spartan detector array covers a 5×5 arcmin field-of-view. In the high-resolution mode, the detector array covers a 2.7×2.7 arcmin field-of-view. With tip-tilt correction, the point-spread function (PSF) is expected to show a spike with a diffraction-limited width in the H (1.65 microns) and K (2.2 microns) bands.
SOAR Adaptive Module (SAM):
The SOAR Adaptive Module (SAM) has been tested on the sky by closing the loop on natural guide stars. It has since been reconfigured for a low-altitude Rayleigh laser guide star in 2011.
Presently, SAM is equipped with a 4Kx4K CCD imager with pixel scale of 45 mas and broad-band B,V,R,I filters. It can use additional filters available at SOAR (SDSS g\', r\', I\', z\' or narrow-band such as Hα, SII, TiO).
Complete sky coverage is achieved because SAM uses the laser for wave-front compensation. The tip-tilt correction is done with two natural guide stars located within 2.5 arcminute radius of the target. The guide stars can be as faint as R=18; they were found for every target observed so far, confirming the expected nearly-complete sky coverage of SAM.
We hope that SAM may be offered as a facility instrument beginning in the 2013B observing semester.
Logistics, Travel, and Accommodation:
Marcela Urquieta – [email protected]
Scientific and Technical Information:
Dr. Steve Heathcote (SOAR Director) – [email protected]
Dr. Sean Points (SOI and Goodman) – [email protected]
Dr. Karianne Holhjem (OSIRIS and Spartan) – [email protected]
Observing and General Contacts:
Brazilian Proposals: Dr. Alberto Ardila – [email protected]
NOAO Proposals: Dr. Sean Points – [email protected]
Other SOAR Websites:
Brazil – http://www.lna.br/soar.html
MSU – http://www.pa.msu.edu/soarmsu
UNC – http://www.physics.unc.edu/research/astro/soar.php
The SOAR Telescope is a partnership among the
U. S. National Optical Astronomy Observatory (NOAO), the Ministry of Science, Technology, and Innovation of the Federal Republic of Brazil (MCTI), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).
Southern Astrophysical Research Telescope
Information herein adapted from SOAR web pages.
For complete information, please see