Work is moving ahead steadily on the SOAR 4.2-m telescope, to be located on Cerro Pachon and operated by CTIO. The SOAR consortium consists of NOAO (30% observing share), Brazil (30%), The University of North Carolina (15%), and Michigan State University (15%). Chile, as the host country, will receive the remaining 10% of the observing time. The basic goals are to build a telescope that produces image quality comparable to that of Gemini and has a package of rapidlyaccessible instruments capable of exploiting that image quality for types of observations optimized to the 4-m aperture.
Caption: Conceptual Design of the SOAR 4.2-m telescope, showing the general arrangement for carrying many instruments simultaneously.
A major milestone was passed in June with the Conceptual Design Review, held in Tucson. Project Manager Tom Sebring and Project Scientist Gerald Cecil led the SOAR engineering team and contractor representatives in a presentation of results of several major preliminary design contracts, which compared different approaches to the mount and active optics system designs, as well as showing initial work on the control software, enclosure, dome, and instrumentation package designs. The outside Review Committee, chaired by Jim Oschmann (Gemini Project Manager) had many helpful comments, but felt that the project generally was in good shape and ready to move into a final design and construction phase.
The general approach is to have only a small inhouse engineering team, with most of the work subcontracted in very major chunks. The project team are currently writing proposal requests for, or negotiating, major subcontracts for the mount (with drives), mirror substrates, Active Optics system (including figuring of M1, M2, M3 and providing their active support systems with all controls), design of the enclosure building and dome, plus a few smaller contracts for the Telescope Control System software, etc.
The telescope building design and preliminary dome design is being carried out by M3, who have done similar work for Gemini and several other major projects. The building construction will be managed by CTIO, who will then subcontract the actual construction work to appropriate companies operating in Chile. As described in a previous Newsletter article (Number 54), the site on Cerro Pachon has been leveled, inaugurated, tested, etc. and is ready to go.
The primary mirror will be a 4.3-m diameter by 10 cm thick meniscus, and will be made of Corning ULE. The goal is to have 4.-2m usable aperture. The primary and secondary mirrors will be supported and controlled with an active optics system such has become standard on all new telescopes. In addition, all foci will be tip-tilt stabilized; the telescope will have only Nasmyth and bentCassegrain foci, all fed by a single tertiary mirror, which will be the element under tip-tilt control. The telescope will be f/16, offering compatibility with Gemini and with NOAO telescopes. As noted above, the primary technical goals of the project are to achieve and exploit very high image quality over the isokinetic patch.
One result of the Conceptual Design Review is that two rather different mount designs would each be capable of meeting the project's specifications. One such design is sketched in Figure 1, which also illustrates the way in which a large number (up to 8-9) instruments can simultaneously be mounted on the telescope. Each of the two Nasmyth ports is shown with "only" a single large Geminisized instrument mounted, but these can instead be occupied by adapter cubes, which offer a selection of three smaller instruments each, with access controlled by an additional folding flat (M4). In addition, there will be 2-3 folded Cassegrain ports, also fed by rotating the tertiary mirror. The time for switching between instruments is specified to be less than 5 min, so that the telescope will be well suited for synoptic and queue observing programs.
The instruments will be produced by the various partners in the project. Proposals have been received for an IR imager, optical imager, optical highresolution IFU spectrograph, and optical highthroughput spectrograph. It is hoped that all of these instruments, plus an infrared spectrograph, can come online within the first year or so of operations, and can be mounted on the telescope simultaneously.
We are aiming to start assembling the telescope in Chile in early 2001 and have it go into service in 2002.
J. Baldwin (jbaldwin@noao.edu)