Jerry Nelson started out studying physics at the Calfornia Insititute of Technology before moving to the University of California Berkeley to complete a PhD in elementary particle physics. A natural tinkerer with things, Nelson grew interested in astronomical instruments, and in 1977 made a proposal to the University of California to build a telescope with a mirror 10 meters across, twice the size of the biggest telescope in the United States at the time.
The size of telescopes had been stalled for decades because they were made of single slabs of glass. Anything larger than around 6 meters was impractically heavy and not rigid enough to hold its shape under gravity. Nelson’s novel solution was to piece together a large mirror from a number of smaller tiles that would be much lighter. He devised a way to grind the tiles into the unusual asymmetric shapes needed and a system of sensors, actuators, and computer control to make the tiles act as a single reflecting surface. It was a risky proposal and university authorities were initially skeptical, but Nelson’s design eventually led to the twin Keck Telescopes on the summit of Mauna Kea, Hawaii, each with a 10-meter mirror made from 36 segments.
Moving to University of California Santa Cruz in 1994, Nelson has won awards from the French Academy of Sciences, the Optical Society of America, the American Astronomical Society, and the optics society SPIE. He has been elected a member of the National Academy of Sciences and SPIE. Now, Nelson is planning to put his scheme to a much stiffer test in the proposed Thirty Meter Telescope, whose mirror will be made up of 492 segments.