And if the crew assigned to man the deep-space mission travels up separately to the station, it would also mean all the elements for their long-duration flight could be launched without the complications of ultra-safe abort systems that complicate manned rockets.

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"We are very pleased that the engine started and continued to thrust, " said Marc Rayman, Deep Space 1's chief mission engineer and deputy mission manager at NASA's Jet Propulsion Laboratory in Pasadena, California.

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Although spacecraft instruments are set to return photographs and compositional data, the encounter primarily is a test of Deep Space 1's autonomous navigation system, the last of 12 technologies the mission was designed to pioneer.

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