CFHT Legacy Survey Data Set

Last update: Thu Oct 25 12:54:59 HST 2012

This collection of pages aims at providing the scientists interested in the CFHT Legacy Survey a large set of information to follow the progress of the survey from the point of view of the data acquired at CFHT using the MegaPrime imager equiped with the MegaCam camera.

The main sections of this site (left menu) provide a wide and complete overview of the status of the CFHTLS: from the observing calendar to the Elixir data releases, various statistics on the survey, an up-to-date summary of the instrument's history, a swirl of catalogs listing the exposure acquired, a full description of the raw and Elixir pre-processed data (pages common with the MegaPrime/MegaCam pages), and the MetaData pages.

MegaPrime/MegaCam is operated exclusively through the CFHT New Observing Process (NOP) composed of QSO, Elixir & DADS. CFHTLS observations (along with regular PI observations) are carried out through Queued Service Observing (QSO), the data are preprocessed (removal of the instrumental signature) and calibrated (photometry and astrometry at the CCD level) by Elixir, and sent to the Canadian Astronomy Data Centre (CADC) in Victoria on tapes by the Data Archiving & Distribution System (DADS). The raw data are also archived at the CADC. The Elixir data are then transfered via the network from CADC to the Terapix data processing center based in Paris. Terapix is primarily focused on handling the CFHTLS data and provides its services to the whole CFHTLS community with the production of the weight and flag map images attached to each megacam image, the data stacking, fine astrometric calibration, and source catalogs generation.

Any CFHTLS registered user is free to download the Elixir data made available at CADC if that user feels confident coping with the data (each image is 700 Mbytes large...). It may however be wise for the ones not experienced in large CCD mosaic data handling to wait for the Terapix data products which are based on an evolved ingestion of the Elixir data, as long as the extra 4 to 5 months needed to get the Terapix data product created and made available at CADC aren't too much of a constraint of course.

The Elixir data come from CFHT along with the MetaData, a large collection of auxiliary data related to the observing process: weather statistics, observer comments, sky transparency for the night, etc... These MetaData are usually sent to the PIs in the form of a CD they can consult through a browser, but for the Legacy Survey the CFHT proposes these pages directly accessible on the web since that information is open to the world (the only elements not made available outside the CFHTLS community are the FITS pixel data, everything else is fully open).

The proprietary period for the CFHTLS pixel data is 3 years for the first year of operation, two years for the second year, and one year for the following years. The survey officially started in mid 2003 and the first pixel data will be made public to the world in August 2006.

Technical note 1: The main menu items on the left marked with an asterisk (*) are external references that will open in a separate window.
Technical note 2: These pages are best viewed with a 1024 pixels wide browser. To avoid text truncations when printing these pages, bring the width first to 850 pixels.