MegaCam is a wide-field imaging camera built for the prime focus of the 3.6m Canada-France-Hawaii Telescope. This large detector has required new approaches from the hardware up to the instrument control system software. Safe control of the three sub-systems of the instrument (cryogenics, filters and shutter), measurement of the exposure time with an accuracy of 0.1%, identification of the filters and management of the internal calibration source are the major challenges that are taken up by the control system. Another challenge is to insure all these functionalities with the minimum space available on the telescope structure for the electrical hardware and a minimum number of cables to keep the highest reliability. All these requirements have been met with a control system which different elements are linked by a WorldFip fieldbus on optical fiber. The diagnosis and remote user support will be insured with an Engineering Control System station based on software developed on Internet JAVA technologies (applets, servlets) and connected on the fieldbus.
MegaCam is an imaging camera with a 1 square degree field of view for the new prime focus of the 3.6 meter Canada-France-Hawaii Telescope. In building the MegaCam mosaic we encountered unprecedented challenges from both the large size of each CCD device (2K x 4.5K with 13.5 micron square pixels each) and the large size of the mosaic in which 40 devices have been assembled in a nearly 4-buttable edge manner on a cold plate. The CCD mosaic flatness of ± 16 μm has been optically checked at its nominal functioning temperature. The CCD mosaic is cooled at 153 K with a cryogenic unit; a close cycle pulsed tube with a power of 90 W at 140 K. A cold capacity, allows a slow warm-up during cooling shutdowns and a thermal dispatching leads to a temperature uniformity better than 3 K on the whole mosaic. The camera cryostat is designed in order to have easy access to the CCDs. The vacuum needed to avoid CCD contamination, leaded us to the use of low out-gassing materials in the cryostat. The instrument was delivered to the observatory on June 10, 2002 and first light is scheduled in October 2002.
MegaCam is an imaging camera with a 1 square degree field of view for
the new prime focus of the 3.6 meter Canada-France-Hawaii Telescope. This instrument will mainly be used for large deep surveys ranging
from a few to several thousands of square degrees in sky coverage and
from 24 to 28.5 in magnitude. The camera is built around a CCD
mosaic approximately 30 cm square, made of 40 large thinned CCD
devices for a total of 20 K x 18 K pixels. It uses a custom CCD
controller, a closed cycle cryocooler based on a pulse tube, a 1 m
diameter half-disk as a shutter, a juke-box for the selection of the
filters, and programmable logic controllers and fieldbus network to
control the different subsystems. The instrument was delivered to the
observatory on June 10, 2002 and first light is scheduled in early
MegaCam is an imaging CCD camera with a 1 square degree field of view for the new MegaPrime prime focus of the 3.6 meter Canada-France-Hawaii Telescope. This CCD camera is fixed on an aluminum structure, called Camembert for its shape, housing a shutter, a filter system and a roll pitch system to tune the CCD mosaic plane. The shutter is made with 1 meter diameter honeycomb half disks that rotates to covers or exposes the CCD mosaic. On this shutter a calibration source is fixed to monitor the CCD and its electronics. The filter system is made of a jukebox with a capacity of eight 30 cm square filters and of a loading arm to place them under the field of view. The instrument was delivered to the CFHT observatory on June 10, 2002 and first light is scheduled in October 2002.
MegaCam is the new wide-field imaging camera currently being built for the new prime focus of the 3.6m Canada-France- Hawaii Telescope. The camera will offer a 1 square degree field of view and is built around a mosaic of 40 2K by 4.5K CCD devices. The delivery of the CCDs is proceeding along the schedule, the project passe dits final design review and the realization phase started, for an expected delivery to CFHT in Summer 2001.