Steve Heathcote and Tom Sebring
The SOAR telescope project passed an important milestone at the end of April with completion of the primary mirror blank. At the same time, visible progress is being made on the construction of the observatory facility on Cerro Pachón. The SOAR (SOuthern Astrophysical Research) Telescope is a joint project involving Brazil, U. North Carolina at Chapel Hill (UNC), Michigan State U. (MSU), and NOAO. The goal is to construct and instrument a 4.2-m telescope offering the highest possible image quality over a tip/tilt corrected field of view about 7´ in diameter. For a brief description of the SOAR telescope and its instrumentation, see NOAO Newsletter No. 59; a detailed account may be found in a comprehensive series of papers presented at the Munich SPIE meeting (http://www.noao.edu/soar/).
The SOAR primary mirror blank was fabricated from ULE low-expansion glass at Corning's Canton, New York, plant using the same production techniques and equipment employed to manufacture the blanks for Subaru and the two Gemini telescopes. It is 4.3 m in diameter, 104 mm thin, and weighs approximately 3200 Kg . The ULE material was purchased as long ago as 1990, but remained in storage for almost a decade while the SOAR consortium undertook the grueling process of raising construction funds for the telescope. The primary was fabricated from hexagonal segments sawn from the ULE boules, tiled together, and then fused at high temperature to form an essentially seamless disk. The layout of the segments within this mosaic was carefully chosen in order to balance any small differences in their coefficient of thermal expansion, thus minimizing thermal distortions of the finished mirror. The substrate was then plano-ground to the correct thickness, heated once more, and allowed to sag over a form to create a meniscus of the required radius of curvature. Then it was carefully annealed to relieve stresses. Finally, both faces of the meniscus were coarse-ground and acid etched to prepare for the subsequent polishing of the mirror. This fabrication process was completed at the end of April, when members of the SOAR project team and representatives from the US partner institutions gathered at Corning's facility to celebrate this important event. The finished primary blank has now been shipped to Raytheon's plant in Danbury, Connecticut, where the mirror will be fine-ground and polished. The blanks for the secondary and tertiary mirrors (both of which are monolithic structures made from the same batch of ULE as the primary) were delivered by Corning in December 1999.
|Caption: Within its steel shipping container, the new SOAR Telescope 4.3-meter mirror blank is ready to go to Raytheon in Danbury, Connecticut, for polishing and figuring. Representatives of the SOAR Partners were at Corning's Canton, New York, facility to celebrate completion of the blank. From left to right are: Bruce Carney (UNC); Eugene Capriotti (MSU); Paul Hunt (MSU); Steve Heathcote, the new SOAR Director; Charles Evans (UNC); Henry Cox (UNC alumnus); and Wayne Christiansen (UNC).|
Meanwhile, the observatory facility building on Cerro Pachón is beginning to take shape. The foundations for the dome and adjacent support building are two-thirds complete, and the pier that will support the telescope mount is nearing completion. The enclosure is now distinctly visible from Cerro Tololo. However, it is not necessary to travel to Chile to watch SOAR take shape. Thanks to SOARCam, one can now view the ongoing construction work by accessing http://www.physics.unc.edu/~evans/soarcam/soarcam.html.
SOARCam is a closed-circuit TV camera, equipped with a long-focus zoom lens, mounted on the side of the Gemini South enclosure some 400 m from the SOAR site. SOARCam, assembled by Charles Evans, was made possible by a donation from UNC alumnus Dr. Henry Cox.
Malcolm Smith and Steve Heathcote stand in front of the pier that will
support the SOAR telescope. In mid-April 2000 the concrete work for the
lower half is complete, with the forms in place to the full height of the
pier. The Gemini South dome is seen in the background.|
Contracts for all the major subsystems of the telescope and enclosure have now been let. The Active Optics System, which includes polishing of the mirrors and fabrication of their active support system, will be executed by Raytheon. The mount, which will be manufactured by RSI Universal Antennas of Richardson, Texas, has successfully passed critical design review and has entered the production phase. Funding has now been secured for three of the four first-generation instruments--the optical imager being built at CTIO under the supervision of Alistair Walker; the Goodman high-throughput optical spectrometer being built by UNC and Brazil under the direction of Chris Clemens; and the IFU-fed, Bench Mounted Optical Spectrometer to be built in Brazil by a group led by Jaques Lépine.
Funding is still being sought for the fourth instrument, a 2K x 2K pixel near-IR imager to be built at Michigan State U. under the leadership of Ed Loh.
The project remains on track towards first light in July 2002 and the beginning of routine scientific operations in mid-2003.