Dan M. Goebel, PhD, is a Senior Research Scientist in the Advanced Propulsion Technology Group at JPL in Pasadena, California. Since joining JPL in 2003, he has worked on the development of high-efficiency ion thrusters, advanced long life cathodes and grids, and electric-thruster life models for deep space missions. He is a world-recognized expert in ion thrusters, cathodes, advanced plasma sources, microwave sources, high-voltage engineering, and pulsed power switches.? Ira Katz, PhD, has led the Advanced Propulsion Technology Group at NASA JPL since 2001. Group accomplishments during his tenure include the development and testing of the 25 kW NEXIS ion thruster, successful completion of the world's longest electric thruster life test, development of technology and support for precision formation flying missions (ST7, Lisa, TPF-I), and laboratory investigations and computer modeling of fundamental electric propulsion physics. Dr. Katz is recognized as a world leader in computer modeling of spacecraft-plasma interactions, spacecraft charging, and ion thruster physics.