Thomas J. Sherrill earned a Ph.D. in astronomy from the University of California, Berkeley, in 1966. He worked for Lockheed Corporation (which became Lockheed Martin Corporation after a 1995 merger) for 29 years, 18 of which were centered on the development of the Hubble Space Telescope, before retiring in 1995. He continues to consult for Lockheed Martin, contributing to advanced mission studies such as for Terrestrial Planet Finder and Constellation-X. Address: 226 Solana Drive, Los Altos, CA 94022. Internet: t.j.sherrill@mindspring.com