The NASA Solar Electric Propulsion Technology Applications Readiness Program (NSTAR) will provide a single-string primary propulsion system to NASA's New Millennium Deep Space 1 Mission which will perform comet and asteroid flybys in the years 1999 and 2000. The propulsion system includes a 30-cm diameter ion thruster, a xenon feed system, a power processing unit, and a digital control and interface unit. A total of four engineering model ion thrusters, three breadboard power processors, and a controller have been built, integrated, and tested. An extensive set of development tests has been completed along with thruster design verification tests of 2000 h and 1000 h. An 8000 h Life Demonstration Test is ongoing and has successfully demonstrated more than 6000 h of operation. In situ measurements of accelerator grid wear are consistent with grid lifetimes well in excess of the 12,000 h qualification test requirement. Flight hardware is now being assembled in preparation for integration, functional, and acceptance tests. Sovey, James S. and Hamley, John A. and Haag, Thomas W. and Patterson, Michael J. and Pencil, Eric J. and Peterson, Todd T. and Pinero, Luis R. and Power, John L. and Rawlin, Vincent K. and Sarmiento, Charles J. and Anderson, John R. and Bond, Thomas A. and Cardwell, G. I. and Christensen, Jon A. Glenn Research Center; Jet Propulsion Laboratory RTOP 242-70-01...