(Spectromètre Imageur à Transformée de Fourier pour l'Etude en Long et en Large de raies d'Emission)

State-of-art wide-field optical integral field unit at CFHT

SITELLE is the optical imaging Fourier transform spectrometer (IFTS) at CFHT that saw first light July 7th 2015 and is now offered for science in the 2016A semester after being successfully tested during the Science Verification phase in January 2015. SITELLE provides integral field unit (IFU) spectroscopic capabilities in the visible (350 to 900 nm) over an 11 by 11 arcminutes field of view, with a variable spectral resolution, depending on the requirement of the observer, from R=2 to R>104 (for low to high spectroscopic studies). For more information on the current status of the instrument, have a look at the FTS-primer.

SITELLE follows the legacy of BEAR, an imaging conversion of the CFHT FTS and the direct successor of SpIOMM, a similar instrument attached to the 1.6-m telescope of the Observatoire du Mont-Mégantic in Québec.

Mounted at the Cassegrain focus of the 3.6m CFH telescope, SITELLE has a field of view of 121 sq.min, and is the largest visible IFU at the time of commissioning. SITELLE covers a field of view 100 to 1000 times larger than traditional IFUs such as GMOS on Gemini or MUSE on the VLT.

The SITELLE focal plane is made of 2 cameras, each of them a four output 2048 x 2048 pixels, low noise, CCD231-42 e2v chip that allows attaining 5e noise in 1 second read time and 3.5 electron in 2 seconds.

The nominal optical seeing of 0.8 arcsec measured at the CFHT site on Mauna Kea in the R band is well sampled by the 0.32 arc.sec pixel scale of SITELLE, making it adequate for most science programs. SITELLE will therefore provide about 1 million independent spectra at once.

SITELLE is typically mounted on the telescope for observing runs centered on the new moon. It shares the dark/grey time with MegaCam.

SITELLE observations are carried out through Queued Service Observing (QSO), the data are preprocessed and calibrated and eventually distributed to PIs through the network by the Data Archiving & Distribution System (DADS). The raw and pre-processed data are also archived at the Canadian Astronomy Data Centre (CADC) in Victoria, and become public after a one year proprietary period.

SITELLE was funded by the Canada Foundation for Innovation with additional financial participation by the CFHT, Université Laval, ABB and e2v. Most of the design and construction work was performed by ABB Analytical, a Québec-based company specialized in Fourier transform spectrometers and optical sensors. Science lead, optical design and its integration were done at Université Laval, the mechanical design and fabrication of the input and output ports at Université de Montréal, while CFHT took charge of the detectors' enclosure and cooling system. "Instrument Description" covers in detail the various parts of the instrument and the entities responsible for building them.

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