36 Foot Telescope, 1975

The surface accuracy of NRAO's 36 foot telescope in Tucson, which began operation in January 1968, fell significantly short of design specifications. In summer 1975, after measuring and mapping the surface to produce a contour map of surface errors, removing the surface paint, projecting the map onto the surface, and marking the contours on the aluminum surface, staff attempted to correct imperfections in the surface by "foiling the telescope." They filled surface "holes" with layers of 0.005 inch thick adhesive aluminum foil. Corrections were less effective than expected. Later the basic problem turned out not to be imperfections in the surface of the reflector but, rather, that the shape distorted with temperature (aluminum structure attached to a steel support structure - bimetallic strip effect) and also with gravity as the reflector tilted. Uncorrectable defects were part of the impetus for replacing the 36 foot reflector with a new 12 meter reflector. In this photo, John Payne (on the left in plaid cap), Paul Rhodes (right), and Victor Gasho (back to camera behind Paul) are hard at work attaching the adhesive foil.

Records of the NRAO

Still Image

laying_foil-2_cleaned.jpg

1975

Photographs Series

36 Foot Telescope Unit