TERAPIX was initially set up in parallel with the development of the new generation wide field imaging facilities for the Canada-France-Hawaii Telescope. This project comprises a new wide field prime focus environment for CFHT, MegaPrime, a new giant visible CCD camera, MegaCam and a new scientific project, the Canada-France-Hawaii Telescope legacy Survey (CFHTLS).
The Canada-France-Hawaii Telescope (CFHT) is a 3.6 meter telescope located at the summit of the Hawaiian volcano Mauna Kea (4200 m). It is operated by Canada (42%), France (42%) and the University of Hawaii. CFHT is one of the world's most famous 4-meter class telescopes thanks to the spectacular scientific results produced there over the last twodecades.
To capitalize on the excellent image quality at CFHT, and to ensure it can remain competitive in the era of 8-meter telescopes, the CFHT Corporation is providing a second generation wide field panoramic CCD camera, MegaCam. MegaCam will be mounted on a new prime focus top end equipped with a new wide field corrector. The camera has 36 CCDs with 2000x4500 pixels each, making it the world's largest CCD mosaic camera. With a field of view of one square degree, it covers four times the area of the full moon. The autofocus and autoguider ensure the best possible image quality at all times. A series of filters cover the entire wavelength range from 370nm to 1000nm.
To maximise the scientific return of this unique instrument, the Canadian and French scientific agencies have decided to set up a huge observational program, the CFHTLS which will address key astronomical and cosmological questions. It consists of three observational programs:
The CFHT-LS "very wide", covering about 1000 square degrees over the ecliptic area and focussed on the Trans-Neptunian and Kuiper Belt observations. Exposure times will be around 5minutes, in three filters only.
The CFHT-LS "wide", covering 170 square degrees over three large fields located at high galactic latitude, in "dust-free" areas of the sky. The wide survey will be focussedon large-scale structure of the Universe, cosmological weak lensing, clusters of galaxies, quasars as well as stellar proper motions in the Galaxy. Exposure times will be about one hour per filter, in 5 filters.
The CFHT-LS "deep", covering four uncorrelated 1 square degree patches (i.e., one MegaCam field) in "dust-free" areas of the sky. The deep survey will be optimised for thedetection of light-curve measurements of Type Ia supernovae and the study of very high redshift galaxies. Exposure times will be between 50 and 100 hours in 5 filters.
The CFHTLS will provide unique insight into the physics of the Solar System, galaxy evolution and the curvature of the universe. The Canadian and French agencies invested 500nights over the period between May 2003 and February 2009.
A main challenge of the CFHTLS is the data handling and image processing. About 50 TB of images will have to be processed, delivered and archived.
The French Institut National des Sciences de l'Univers (INSU), the Commissariat a l'Energie Atomique (CEA), the Programme National Cosmologie et Galaxies (PNCG) and the Institut d'Astrophysique de Paris have funded and set up an image processing center. This center, called Terapix (Traitement Elementaire, Reduction et Analyse des PIXels de MegaCam), is an astronomical data reduction centre dedicated to the processing of extremely large data flows from digital sky surveys.
TERAPIX is located at IAP (Institut d'Astrophysique de Paris). Its primary tasks are:
to develop image processing and pipeline software for MegaCam and WIRCam;
to develop and provide tools for handling of large CCD visible and near infrared images;
to operate the final reduction pipeline to produce calibrated images and catalogues of MegaCam and WIRCam images;
to provide technical assistance and Terapix computing facilities to MegaCam users.
The TERAPIX group is currently composed of 4 engineers and 3 astronomers.
The PI is Yannick MELLIER.
Institut d'Astrophysique de Paris
98 bis Boulevard Arago
75014 Paris FRANCE
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