Dr. Johnson is currently the Chief Scientist for the Solar System Exploration Directorate, where his responsibilities include program development for future exploration missions. He is an expert in the geophysics and geochemistry of the satellites of the outer solar system. He has participated in all of JPL's major missions to the outer solar system, both as a researcher and a scientific leader. He was a member of the Voyager Imaging Team and NASA's science definition teams that developed the concepts for Galileo (for which he was Project Scientist) and Cassini (where he is involved with two experiments).

During Dr. Johnson's career at JPL, he has been involved in several NASA/JPL projects:

• Voyager - Imaging Science Team, chair of Satellite Science Working Group
• Galileo
• Project Scientist
• Near Infrared Mapping Spectrometer - Co-I
• Cassini
• Imaging Science Team
• Co-I Cosmic Dust Analyzer
• Other missions - participated in studies, proposals, pre-phase A and phase A studies of numerous missions at various levels, including
• Lunar Polar Orbiter - Project Scientist phase A - mission never started
• Mariner Jupiter Uranus - Science advisory committee and PI of instrument proposal - mission never started
• Halley-Temple 2 - instrument proposals - mission never started
• Mars Observer - selected for Infrared spectrometer facility team - instrument de-scoped before launch
• CRAF - selected for VIMS facility - mission canceled
• Jupiter Icy Moon Orbiter - Project Scientist - mission indefinitely deferred

Managerial Roles - last 5 yrs:

• Chief Scientist, Solar System Exploration Directorate

• Fellow, American Geophysical Union
• Member, American Academy of Arts and Sciences
• Fellow, American Association for the Advancement of Science
• Member, International Academy of Astronautics
• COSPAR, Chairman of Commission B (2004-2012) , lunar and planetary exploration
• Honorary Degrees, Laurea ad Honorem in Astronomica, University of Padua, Italy
• Past-President, Planetology Section, American Geophysical Union
• Chair, Honors and Recognition Committee, American Geophysical Union
• NASA Awards
  • Multiple Group Achievement Awards
  • Exceptional Scientific Achievement Medal (2)
  • Exceptional Service Medal
  • Outstanding Leadership Medal
• Ansari Best Reference Work Award (2008) for Encyclopedia of the Solar System, 2nd Ed, with co-editors Paul Weissman(JPL) and Lucy McFadden, from GeoScience Information Society
• Advisory Committees, Dr. Johnson has served on numerous NASA and NRC advisory and review committees - a few of the more significant are listed below
  • NASA Space Science Advisory Council
  • NASA Outer Planets Probe science working group
  • NASA Jupiter Orbiter Probe (later Galileo) Science advisory group
  • NASA Joint Assessment Team for Cassini/Huygens
  • NASA Strategic Roadmap for Solar System Exploration
  • NRC Decadal Survey of Solar System Exploration, Large Satellite sub-panel
• Conference and meeting organization - Dr. Johnson has participated in many science conference activities over his career, including as Planetology Section Program chair for the AGU, serving on the Division for Planetary Science and Lunar and Planetary Science Conference Program Committees several times, the US National Committee for the IUGG, and organizing a pre-Voyager AGU Chapman conference on the Jupiter system.
• Asteroid 2614 Torrence named in honor of contributions to asteroid science.

Dr. Johnson has published over 177 referred publications