The sticking point was the central mirror. The diameter of the mirror, a giant round disk of glass whose surface is exquisitely polished to ensure maximum accuracy, determines how much light the telescope can capture and how sharp an image it can create.
Building a mirror larger than five meters is a Catch-22: It needs to be thick enough to support its weight and not collapse, but the mass required to do that can cause gravity to change the shape of the mirror when it moves.
Rather than use a single concave mirror, Mr. Nelson, along with the physicist Terry Mast and the engineer George Gabor, proposed using 36 smaller hexagonal mirrors, arranged in a honeycomb-like pattern, to make one large one.
Each interlocking piece, about 6 feet wide and 3 inches thick, would be supported and rearranged by a computer to maintain its correct position.
It was a radical idea, and it required a level of precision that many thought impossible. “They told us we couldn’t electronically glue together broken pieces of glass,” Mr. Gabor told The Los Angeles Times in 1993.
Today, the design is the basis for many advanced telescopes, both on the ground and in space.
Jerry Earl Nelson was born on Jan. 15, 1944, in Glendale, Calif., to Julian Bonne Nelson, a machinist for Lockheed, and the former Leona Jeanette Hill, who managed the local children’s park.
After attending Verdugo Hills High School in Los Angeles, Mr. Nelson received a B.S. in physics at the California Institute of Technology in 1965 and a Ph.D. in physics at the University of California, Berkeley, in 1972. He worked as a staff researcher at the Lawrence Berkeley National Laboratory from 1970 to 1981 and taught astronomy at Berkeley from 1981 to 1994.
He spent the early 1990s in Hawaii as a project scientist during the construction of the Keck telescopes, before returning to the mainland and taking a position as a professor of astronomy at the University of California,…