Initiated in 1994, the New Millennium Program carried out two low-cost, technology-focused missions in the 1990s, Deep Space 1 and Deep Space 2.
The Deep Space 1 mission's primary goal was to demonstrate solar electric, or ion, propulsion, related navigation technologies, and new electronic, communications and instrument technologies. Launched Oct. 24, 1998, Deep Space 1 navigated to comet Borelly, where it made a very close pass on Sept. 22, 2001. It captured the highest-resolution imagery of a comet nucleus in existence.
The Deep Space 2 mission consisted of a pair of penetrator probes carried to Mars on the 1999 Mars Polar Lander. These were lost along with the Polar Lander.