SCUBA-2   Infrastructure Project

JCMT Shutdown 13-February to 17-August 2006

SCUBA-2 is a new instrument for the JCMT.  It is an extremely sensitive continuum array receiver which, due to its size, cannot be mounted easily on the telescope. Significant development of the facility is required to mount the instrument and its supporting equipment and provide servicing capabilities. The ‘SCUBA-2 Infrastructure Project’ was developed to provide these facilities. As part of the implementation of the project a telescope shutdown is required lasting six months.

Key elements of the project are:

The Gallery

A new gallery above the control room to site the support equipment for SCUBA-2 including closed cycle cooling equipment, dilution refrigerator rack and all electronics other than the MCE array controllers. This gallery was installed prior to the shutdown and was ready for the installation of power supplies and coolers as part of the shutdown work.

Receiver cabin modifications

The receiver cabin will house a new Tertiary Mirror Unit and a set of relay optics to reduce the SCUBA-2 input beam to a size that can pass unvignetted through the left elevation bearing. To house these ‘cabin mirrors’ significant redevelopment of the receiver cabin is required.  This includes relocation of existing equipment and modification of the cabin bay next to the bearing.

Left Hand Nasmyth Platform

The left hand Nasmyth Platform that serviced the original SCUBA and allowed access to the receiver cabin has to be virtually eliminated to mount the re-imaging optics and the instrument itself.  Key work during the shutdown is removal of the existing platform and rebuilding of the receiver cabin access walkway.  A further part of this work is extending the mezzanine platform below to allow access to SCUBA-2 when installed.

SCUBA-2 mounting structure

SCUBA-2 requires a mounting frame to support the instrument and the re-imaging ‘Nasmyth mirrors’.  This structure is being design and fabricated by contractors and will be installed by ETS staff towards the end of the shutdown.

Instrument Handling and Servicing

The mass of SCUBA-2 (~4 ton) is too heavy to be supported on the antenna and carousel floor by conventional means. As a result a significant part of the project is to provide dedicated handling equipment to install and remove the instrument. The Carousel floor requires strengthening and the installation of a rails system for a handling cart to run on.  The ETS will be installing this reinforcement during the shutdown with the handling cart arriving towards the end of the period.

Simon Craig, JAC Chief Engineer

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