The use of low power electric propulsion systems have been pioneered by the AFRL and STP. The AFRL IHPRPT Program is also investing in the development of long life low power HET systems. A key technology identified in the Beyond IHPRPT study is an extremely long life and low mass variant of the BHT-200 and 600 HET systems. The multi-functional converter concept is attractive for its reduction in overall propulsion system mass complexity and cost. Commercial satellite manufacturers; SS/L, Boeing, Lockheed Martin and Orbital Sciences have all shown a strong interest in low power HET systems for primary propulsion on LEO spacecraft and station keeping on GEOSats. Hall thrusters have been identified as a key technology for NASA's vision of space exploration. NASA missions beyond Earth orbit can be enabled by the wide throttle range and broad Isp-thrust operation of electric thrusters. A study conducted by the SMD ISPT Project in 2004 confirmed the significant potential of REP for space science, especially with recent advancements in enabling, high ¬ñspecific-power RPS technology (from 3 to over 8 We/kg). The study also concluded that REP would be ready for near-term NASA science missions if an electric propulsion thruster with the appropriate specific impulse and propellant throughput capability could be developed. Evaluations and assessments performed over the last decade have confirmed the benefits of REP for a variety of potential missions, including orbiters about Pluto, Neptune, and Uranus; rendezvous and Centaurs, Kuiper Belt Objects and primitive bodies in the outer Solar System; and extensive surveys of major asteroid groups. In general, REP offers the benefits of nuclear electric propulsion without the need for an excessively large spacecraft and power system.