The ion engine on the experimental Deep Space 1 (DS1) spacecraft shut down just a few minutes after it was used for the first time Tuesday, November 10.

Mission controllers were able to recover the spacecraft from a "safe mode" Friday, November 13, two days after a problem with a star tracker stopped normal operations.

The engine, one of the showcase pieces of new technology on the spacecraft, shut down 4 1/2 minutes after it was started around 2:30 pm EST (1930 UT) November 10. The cause of the shut down is not known, and efforts to restart the engine Tuesday failed.

The engine test was the first time the ion engine had been used to propel the spacecraft. The engine had been powered up and checked out prior to Tuesday's test, without any problems.

JPL, the center running the DS1 mission, noted that ion engine "turn-off" has been seen in ground tests and in Earth-orbit spacecraft before. "Deep Space 1 is designed to test and validate the use of such propulsion in deep space for the first time, so the ongoing diagnosis of Tuesday's behaviour is in keeping with the mission's goals," mission officials reported in a statement.

The spacecraft collected "valuable diagnostic data" during the engine problems, JPL reported, and also noted that all the other systems on DS1 appeared to be functioning normally.

On Wednesday, November 11, DS1 entered a "safe mode" when software on the spacecraft detected a problem with a star tracker. The tracker, used to determine the orientation and location of the spacecraft, lost its lock on a star. Efforts by the onboard fault-protection software to correct the problem failed, so it placed the spacecraft into a safe mode to await commands from Earth.

Engineers on the ground were able to get the star tracker working again, but are unsure if it is a problem with the tracker itself or software used to communication between the tracker and the spacecraft's other systems. Controllers were able to put the spacecraft back into normal cruise operations on Friday, November 13

JPL reported that engineers will not work with the ion engine until late next week, more than a week after the problem first appeared. In the meantime other spacecraft systems, including instruments and control systems, will be checked out.

DS1 is the first mission of the New Millennium Program, a NASA effort to develop and flight-test new technologies that can be used in future missions. The ion engine in DS1 is one of the key technologies being tested on the mission, as well as advanced solar panels, autonomous control systems, and scientific instruments.

DS1's prime mission is to test the new technologies, however, there are science plans for the mission as well. The spacecraft, launched October 24, is scheduled to fly by the asteroid 1992 KD in July 1999, and may fly by two comets in 2001 if the mission is extended. To meet those goals, though, the ion engine must work, as the spacecraft has no other propulsion system.