<class=a"Academic and Professional Appointments: <class=a"1966, Fellow, Lick Observatory< <class=a"1967-1968, Postdoctoral Research Fellow, Kellogg Radiation Laboratory, <class=a" California Institute of Technology< <class=a"1968-1972, Assistant Professor of Astronomy, University of Texas at< <class=a" Austin< <class=a"1970-1977, Consultant, Jet Propulsion Laboratory, Pasadena, California< <class=a"1972-1982, Consultant, NASA Headquarters, Washington, DC< <class=a"1972-1986, Consultant, Lawrence Livermore National Laboratory, Livermore, California< <class=a"1972-1975, Associate Professor, Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona< <class=a"1973 National Academy of Sciences Exchange Scientist to the USSR O. Yu. Schmidt Institute of Geophysics, Moscow) <class=a"1975- Professor, Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona< <class=a"1977, Acting Director, Lunar and Planetary Laboratory, and Acting Head, Department of Planetary Sciences, University of Arizona< <class=a"1978-1981, Director, Lunar and Planetary Laboratory, and Head, Department of Planetary Sciences, University of Arizona<