A 10-Meter Telescope for Millimeter and Sub-Millimeter Astronomy

Abstract

The design and construction of a prototype 10.4 meter, f/0.4 telescope intended for millimeter- and submillimeter-wave astronomy is described, with particular emphasis on design features, fabrication techniques, and error sources. The surface accuracy attained on a prototype dish was about 50 µm rms; on the first of four "production" dishes, about 25 µm rms; the goal for at least one of the four dishes is to be 10 µm rms or less. The reflecting surface is sheet aluminum cemented to accurately machined honeycomb panels. The 84 demountable panels are supported on a tubular steel- framework which is itself disassemblable into a few easily transportable pieces. A notable feature is that the dish may be disassembled and reassembled without significant loss of accuracy and without need for later readjustment, although the means for readjustment are provided. The mount is of the altazimuth fork type and has an initial absolute pointing accuracy of 6 - 10" and a tracking accuracy of 1 - 2" in the absence of strong wind gusts, which degrade the tracking accuracy somewhat. The telescope, operated in an f/4.2 cassegrain mode at 230 GHz, has a system effeciency greater than 50 percent. Three such telescopes are to be installed at Owens Valley Radio Observatory and used as a millimeter-wave aperture synthesis radio interferometer. A fourth telescope, of especially high dish accuracy, is to be built and tested at OVRO and later moved to a high, dry mountain site for submillimeter infrared and radio astronomy.