1. Member of the Technical Staff at the Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-501, 4800 Oak Grove Drive, Pasadena 91109.
2. Director of operations of the National Astronomy and Ionosphere Center, Box 995, Arecibo, Puerto Rico 00613.
3. Director of the Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138.