Welcome to the first of what I intend to be a regular contribution to Cassiopeia. The James Clerk Maxwell Telescope is the world’s premier submillimetre observatory. It is one of three telescopes on Mauna Kea in which Canada has a share, and the only one with a Canadian as Director. In this article I will present an update on the instrumentation programme and the prospects for the future of the facility.
After several years of stable operation during which the SCUBA instrument set the worldwide standard for submillimetre astronomy, the obervatory is currently in the midst of an aggressive programme of development in which the entire instrument suite is being replaced: the DAS by ACSIS, our new multi-channel correlator; RxB by HARP, a 16-pixel heterodyne array for the 345-GHz band; and SCUBA by SCUBA-2, the next-generation continuum camera currently under development. In addition, we are developing an interferometry mode for sub-arcsecond astronomy in collaboration with the SMA and the CSO. This instrumentation programme is an essential component of our strategy for maintaining the facility at the forefront of submillimetre astronomy.
Our new suite of heterodyne instruments consists of four components:
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Figure 1: ACSIS, in position on the carousel floor of the JCMT. |
This suite of instruments is currently being commissioned and I anticipate releasing it to the community, with the exception of ROVER, for semester 07A. ROVER will follow in due course. During the first phase of commissioning in February 2006, HARP/ACSIS obtained the map around the Orion nebula in Figure 3 in under two hours; with the previous instruments it would have taken nearly two months of continuous observing with the JCMT to map this area of sky.
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Figure 2: HARP on the right Nasmyth platform of the JCMT. |
Figure 3: Image in Orion obtained with HARP/ACSIS during commissioning. |
So, what of our current heterodyne instruments?
SCUBA-2 is the next-generation continuum camera for the JCMT. It is designed to capitalise on the enormous success of SCUBA by providing a wide-field continuum mapping capability of unprecedented scope. This improvement will be achieved through three technical innovations: better per-pixel sensitivity, a much larger field of view, and novel scanning and sampling modes. These factors combine to enable to SCUBA-2 to map large areas of the sky up to 1000 times faster than was possible with SCUBA, opening up the prospect of large-scale submillimetre surveys for the first time. The instrument development is led by the UK ATC in Edinburgh in collaboration with the University of Cardiff and a consortium of Canadian universities. The detector technology is being developed at the National Institute of Standards and Technology in Boulder, while the silicon micro-machining is performed by the Scottish Microelectronics Centre at the University of Edinburgh, supported by commercial vendors.
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Figure 4: SCUBA 850µm image of the Galactic centre (inset). |
Figure 5: Bryce Burger, Mark Halpern and Mandana Amiri (all UBC) with the prototype SCUBA-2 multi-channel electronics. |
As one example of the revolutionary capabilities of this instrument, the inset of Figure 4 shows the largest single map ever taken using SCUBA; it required 120 hours of excellent weather. SCUBA-2, however, will be able to map the entire area shown in the figure to the same depth in just a couple of hours. SCUBA-2 will thus initiate a new paradigm in submillimetre astronomy, in which we move from the study of individual objects to the study of statistically-significant samples.
Canada has a prominent role in this highly-innovative project. Supported by an award from the CFI (PI: Mike Fich), three components of the project are being undertaken in Canadian universities:
In addition, and supported from the same award, Canada will be supplying two ancillary common-user instruments for use in conjunction with SCUBA-2:
SCUBA-2 is currently scheduled for delivery to the JCMT in the spring of 2007, and early science operations will commence in semester 07B. Commissioning of FTS-2 and POL-2 will follow some time thereafter.
SCUBA-2 will be by far the largest instrument ever installed at the JCMT, and accommodating it on the telescope as a facility instrument represents a massive engineering challenge. The JCMT was therefore closed for a period of six months, from mid-February to mid-August, in order to carry out this construction work (Figure 6). The engineering staff worked long hours under difficult conditions to bring this project to a successful conclusion. As I write this article, JCMT science staff are working hard to re-commission the observatory for common-user observing.
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Figure 6: SCUBA-2 mounting frame secured on the JCMT, in the location formerly occupied by SCUBA. |
In recognition of the potential of HARP/ACSIS and SCUBA-2 for large area mapping, the JCMT Board approved in July 2005 an ambitious set of legacy surveys for the JCMT. The survey programme was allocated 55% of UK/Ca/NL time over four semesters, which in average conditions would correspond to 265 nights. The Board also approved a further 307 nights, in principle, over the years 2009–12; this latter approval is conditional on continuation of the JCMT beyond 2009 (about which more below) and is subject to renewed competition. The seven survey projects are as follows:
These seven projects are led by coordinators, in many cases one from each of the three JCMT partner countries. Canadian coordinators are James Di Francesco, Mark Halpern, Doug Johnstone, Brenda Matthews, Rene Plume, Douglas Scott and Christine Wilson.
4. Submillimetre Interferometry: The eSMA Project
The eSMA is a collaboration between the JCMT, the SMA and the CSO to combine the three observatories into a single interferometric array with roughly twice the collecting area of, plus more and longer baselines than, the SMA acting alone. The eSMA will operate part-time and in the 345-GHz window, taking full advantage of Mauna Kea’s excellent observing conditions and prolonged periods of superb weather at that frequency. With spatial resolutions of ~0.15”, this will bring a subarcsecond capability to the JCMT for the first time and well in advance of ALMA.
Although the project has been in the works for several years, commissioning began in earnest in 2005 and first fringes between the SMA and JCMT were obtained at 267 GHz in July, followed by first spectra in September. The commissioning will be resumed this autumn, following the hiatus forced by the JCMT closure. The agreement between the three observatories calls for a Pilot Programme at 345 GHz, consisting of 42 nights spread over 12 months, to fully characterise the system. The Pilot Programme will commence in 2007 and Canadians will have access to this time through a conventional proposal process.
5. The Future of the JCMT
The future of the JCMT is extremely promising. The new instrument suite described above will open up new observational paradigms in submillimetre astronomy; SCUBA-2, in particular, will have no competition for the foreseeable future, and I expect it to revolutionise the field just as its predecessor SCUBA did.
The tripartite agreement between the three agencies which fund the JCMT is currently set to expire in May 2009. In preparation for this deadline, the JCMT underwent a comprehensive strategic review in 2005, chaired by Martin Harwit (Cornell). The review was extremely successful: the panel praised the JCMT’s historical record of scientific productivity and its ambitious plans for the future. The panel’s report is available from the JCMT website.
Given the strong endorsement of the JCMT by the Harwit panel and the large investments which have been made in the new instrumentation suite, the case for continuation of observatory operations beyond 2009 is extremely compelling. As a consequence, all three agencies have indicated their wish to continue funding the JCMT until at least 2012, and are seeking the required funds from their governments. A final decision is anticipated by the end of 2006.
