The reasons for preferring to build upon the existing CFHT are fully described in the above section. Nevertheless, we are aware of, and remain sensitive to the interests and constraints affecting our existing CFHT partners: the Institute for Astronomy at the University of Hawaii and France. We also note that the Gemini directorate has expressed interest in developing a third 8m telescope, albeit in the context of a technology demonstration platform aimed at a VLOT. Here, we comment on these issues and also the prospects for alternative partnerships.
The planning discussions for the existing CFHT largely took place prior to first light at VLT (May 1998) and, of course, the more recent activities at Gemini-North and Subaru on Mauna Kea. The image quality being delivered by these new 8m is astoundingly good and it is quite clear now that CFHT (the traditional leader in image quality) is about to be supplanted by these much larger telescopes. This is an important competitive issue and the implications of these results are only now being digested.
Our conclusion, as argued in the preceding sections, is that the competitive position of CFHT, even up to the 2005 era, has been compromised. There is also widespread recognition now that the world community will not be in a position to construct a VLOT prior to 2010. The thrust of the proposal developed here is to have first engineering light in 2004 and scientific use by early-2005. There is much common ground shared by our scientific communities, which can provide the basis for discussions to implement the vision developed here. The position of the Canadian community is clear, but we do recognize that any project involving CFHT must be negotiated within the framework of the existing partnership. We also recognize that one or more new partners may have to be brought into the existing partnership in order to secure full funding of the new 8m.
Another option is to replace the CFHT with an 8m built on a different site on Mauna Kea. This has the attractive feature of permitting continued operation of the present CFHT during the construction phase, minimizing the amount of observing time lost and allowing the new wide-field CFHT instruments (Megaprime and WIRcam) to carry-out their intended programs without constraint. The cost of a building an entirely new facility may be slightly higher, primarily because of the need to pour a suitable concrete pier to support the telescope, but other cost saving features of the CFHT-based proposal remain. The most obvious possibility, which has been informally discussed with the IFA Director, is to replace the University of Hawaii 2.2m telescope. Under this option, Canadian operational support for the current CFHT would be reduced, or cease altogether (depending on our share of the new facility) upon the start of science operations with the replacement facility.
The alternative-site option need not be restricted to UH as there are two other aging 4m-class facilities on Mauna Kea; UKIRT and the IRTF. UKIRT, an infrared optimized telescope, is operated by the UK Agency PPARC through the Joint Astronomy Center in Hilo (JAC is also the management organization for the JCMT and hosts the Gemini North headquarters). Discussions with the UK on this and other partnership possibilities are to be encouraged. The IRTF is managed by the IFA on behalf of NASA and the status of this site for possible redevelopment is unknown at this time.
Some interest has been expressed by the Gemini consortium in building a third 8m telescope, partly to satisfy the expected pressure from the community for observing time, and partly to serve as a platform for demonstrating novel technology needed for the construction or operation of VLOT. This has been a traditional activity (e.g.; the ESO NTT was constructed to gain experience with an active mirror support system to be used on the VLT.) At this time, there is no clear definition of precisely what area of new technology might be incorporated into the third 8m, but some possibilities may be discerned from existing studies of MAXAT (Maximum Aperture Telescope).
Hence an option to be considered is the replacement of CFHT by the third Gemini 8m, an option that might be facilitated by the current Canadian participation in Gemini. There are, however, several factors that mitigate against this as a satisfactory response to the proposal developed here. These include:
- the cost of a ``NewTech'' 8m will almost certainly exceed the cost of the telescope proposed here which uses proven, existing designs;
- the Canadian share of Gemini (13.2%) does not provide sufficient access to 8m time and therefore either a new sub-partnership would be needed or some additional facility identified to meet the Canadian demand for 8m access;
- the time scale for this facility may be outside the window defined here; and
- the design may be driven by considerations other than the scientific case presented here.
None of the above factors are necessarily fatal and thus the concept outlined above deserves exploration if the other, simpler initiatives flounder. The attractive features here are that this option provides a path in which the design and eventual construction of a VLOT can be foreseen within the context of existing Canadian partnerships, and it offers a possible path toward rationalizing the Canadian optical/IR facilities under a common operational structure.
To summarize, the preferred path is a straightforward replacement of the existing CFHT with a new 8m, but other options, which have the potential to meet all the scientific goals defined here, do exist.