WIRCam (Wide-field InfraRed Camera)

State-of-art near-IR wide-field imaging at CFHT

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WIRCam, is the near infrared mosaic imager at CFHT, which saw first light in November 2006 and has been offered for science in all observing semesters since February 2006. Its wide field imaging capability in the near-infrared was designed to closely complement the 1 sq.deg optical imager, MegaCam, which has been in operation at CFHT since 2000. Taken together, both these instruments make CFHT unique on Mauna Kea with the capability of wide field imaging extending from the ultra-violet uĠ-band all the way to the Ks-band at 2.2microns.

Mounted at the prime focus of the 3.6m CFH telescope, WIRCam has a field of view of 20 sq.min , and represented one of the largest astronomical mosaic of infrared detectors at the time of commissioning. Since then it continues to offer unique near infrared capabilities in both broad and narrow band imaging suitable for a wide variety of survey and PI programs. Its nominal oversubscription rate of 1.5 to 2 in any observing semester clearly shows its continued popularity with the observing community.

The WIRCam focal plane is made of a mosaic of four HAWAII2-RG detectors, each containing 2048 x 2048 pixels, with a sampling of 0.3 arc second per pixel. WIRCam is fitted with an image stabilization unit (ISU) using on-chip guiding. During an exposure, the image stabilization signal is obtained by repeatedly reading out a small, 14x14 pixel region centered on a bright star on each of the four detectors, while the integration continues uninterrupted for the rest of the pixels.

The nominal near-infrared seeing of 0.8 arc.sec measured at the CFHT site on Mauna Kea is well sampled by the 0.3 arc.sec pixel scale of WIRCam, making it adequate for most science programs. However, occasionally the seeing has been observed to improve to 0.5 arc.sec or better, under which the PSF becomes undersampled. In order to facilitate science programs which can benefit from such exceptional seeing conditions, WIRCam can use its image stabilization unit to micro-step the image with 0.15 arc.sec sampling. Such Microdithering capability is offered for wide-band filters only.

As the near-infrared instrument at CFHT, WIRCam is typically mounted on the telescope for 10-day observing runs centered on the full moon. It shares the bright time with the high dispersion echelle spectrograph, Espadons. However, depending on program pressure, the length of the WIRCam observing run may on occasion be extended into the dark time normally devoted to MegaCam observing. With this large share of telescope time, WIRCam is available for a variety of programs, extending from PI programs of a few hours to large multi-semester public surveys comprised of many nights of observing. Z

WIRCam is operated exclusively through the CFHT New Observing Process (NOP). Observations are carried out through Queued Service Observing (QSO), the data are preprocessed (removal of the instrumental signature) and calibrated (photometry and astrometry) by `I`iwi (an Elixir equivalent for WIRCam), 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. The Terapix data processing center based in Paris proposes its services to the whole CFHT community with the data stacking, fine astrometric calibration and catalogs generation.

WIRCam was funded through the instrumentation fund by the Canadian and French Agencies (NRC and CNRS/INSU), and by special contributions from the Korea Astronomy Observatory and from the Cosmology and Particle Astrophysics consortium (CosPA) of Taiwan. The Observatoire de Grenoble and University of Montreal were contracted for the design and fabrication of major parts of the instrument. "Instrument Description" covers in detail the various parts of the instrument and the entities responsible for building them.

Note to the Principal Investigators preparing a time proposal: All the information relevant to the preparation of a time proposal and/or preparing the time distribution for the QSO's PH2 phase can be found in the "Specifications & Performance" and " New Observing Process" sections of the left menu (instrument specifications, exposure time calculator, etc...).

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