Discovery's astronauts had trouble aiming a "Star Wars" research satellite after releasing it in orbit Wednesday, and ground controllers postponed the first observation of shuttle exhaust plumes.

The experiment was delayed after wrong maneuvering commands twice were sent to the satellite.Mission Control told the crew to forget the plume experiments until later in the day, while ground controllers rushed to solve the problem.

"If we can get this sorted out, we'll pick up three burns . . . a little bit later on," Mission Control's Brian Duffy said.

The first observation of a maneuvering engine burn had been scheduled for Wednesday morning, with two more early Wednesday evening. The crew also had planned to observe the plume of a smaller steering jet firing this evening.

The astronauts used the shuttle's robot arm Wednesday to lift the 15-foot satellite from Discovery's cargo bay, then released it.

A few minutes later, commander Michael Coats steered the shuttle away from the satellite to put 6.2 miles between the two craft.

The trouble began a few hours later.

A sensor to protect the satellite's instruments from the sun was turned on as planned. Suddenly, the spacecraft's position changed, apparently because the sensor detected a bright light, said NASA flight director Bob Castle.

Controllers gave the astronauts two sets of computer commands to correct its alignment and both sets contained errors, putting the satellite in the wrong position, Castle said.

Mission Control delayed the first observation by one orbit, or 90 minutes, then by about nine hours after it became apparent the problem would not be resolved quickly.

The $94 million satellite - a two-ton set of instruments resembling a barrel on a platform - was supposed to spend 11/2 days gathering data from the exhaust and from chemical and gas clouds that will be released from the shuttle.

Pentagon officials said the information is needed to develop sensors that can "read" an enemy missile's exhaust and distinguish it from natural phenomena, such as the aurora or northern and southern lights, and from manmade clouds used to camouflage warheads.

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(Additional information)

USU scientists cheer test

When scientific instruments on the space shuttle Discovery locked on the aurora australis, the Utah State University contingent at Johnson Space Center erupted in jubilation.

"We just had all kinds of cheers and applause," said Edward Vendell of Ogden, a USU professor of aerospace engineering. "We were witnessing a large aurora oval of intensity beyond belief."

USU is involved in three Discovery-launched experiments related to the Strategic Defense Initiative, including one experiment scheduled to take numerous readings of the two auroras.

Due to recent solar activity, Vendell said, astronomers had been predicting an aurora display. "But this was more than we expected. We are just delighted. We'd hoped to see aurora activity, but it's extremely rare to have aurora activity of (Monday's) intensity."

USU researchers had opened the lens on their Cryogenic Infrared Radiance Instrument for Shuttle, or CIRRIS, just in time to record the natural light show.

The telescopelike device is anchored in the shuttle cargo bay and uses infrared sensors and a radiometer to obtain information on the infrared character of the Earth's upper atmosphere.

*****

(Additional information)

USU scientists cheer test

When scientific instruments on the space shuttle Discovery locked on the aurora australis, the Utah State University contingent at Johnson Space Center erupted in jubilation.

"We just had all kinds of cheers and applause," said Edward Vendell of Ogden, a USU professor of aerospace engineering. "We were witnessing a large aurora oval of intensity beyond belief."

USU is involved in three Discovery-launched experiments related to the Strategic Defense Initiative, including one experiment scheduled to take numerous readings of the two auroras.

Due to recent solar activity, Vendell said, astronomers had been predicting an aurora display. "But this was more than we expected. We are just delighted. We'd hoped to see aurora activity, but it's extremely rare to have aurora activity of (Monday's) intensity."

USU researchers had opened the lens on their Cryogenic Infrared Radiance Instrument for Shuttle, or CIRRIS, just in time to record the natural light show.

The telescopelike device is anchored in the shuttle cargo bay and uses infrared sensors and a radiometer to obtain information on the infrared character of the Earth's upper atmosphere.