The Canada-France-Hawaii Telescope (CFHT) has been in operation since 1979. The Telescope Control System (TCS)
has undergone software changes since the beginning of science operation but the original hardware has largely been
untouched except for an upgrade to the time system and host computer. Telescope performance has not been an issue
although some improvements are desirable. However, parts obsolescence will become a problem as the telescope enters
it third decade of operation. Although there are sufficient spare parts currently, many are no longer readily available.
Some critical components, such as encoders and VME CPU boards are no longer available. The TCS upgrade project
addresses the obsolete and obsolescent issues to ensure operational capability through 2025. It seeks to modernize and
simplify the electronics and to take advantages of the advancement made in stand-alone servo controllers.
In 2007, the Canada-France-Hawaii Telescope (CFHT) undertook a project to enable the remote control of the
observatory at the summit of Mauna Kea from a control room in the Headquarters building in Waimea. Instead of
having two people operating the telescope and performing the observations from the summit, this project will allow one
operator to remotely control the observatory and perform observations for the night. It is not possible to have one person
operate from the summit, as our Two Person Rule requires at least two people for work at the summit for safety reasons.
This paper will describe how systems engineering concepts have shaped the design of the project structure and
execution.
The Canada-France-Hawaii Telescope is now operating a wide-field visible camera with a one-degree field of view. We have developed a guiding and auto-focus system that uses two stage-mounted CCD cameras fed by Shack-Hartmann optics providing position and focus error signals to the telescope guiding and focus control systems. The two camera stages patrol guide fields separated by more than a degree, one to the north and one to the south of the main camera field. Guiding generates a 50 Hz correction signal applied to a tip-tilt plate in the light path and a low frequency correction signal sent to control telescope position. During guiding a focus error signal is used to adjust telescope focus. Calibration issues include guide camera focusing, image distortion produced by the wide field corrector, guide stage positioning, and determining ideal guide star positions on the cameras. This paper describes the resulting system, including preselected guide star acquisition, guiding, telescope focus control, and calibration.
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