With a $94 million "Star Wars" satellite looking on, the shuttle Discovery wrapped up a series of spectacular rocket firings Thursday in an unprecedented experiment to learn how to spot enemy rockets in space.

Trailing the SPAS-2 satellite by just 11/2 miles, the shuttle crew fired Discovery's twin braking rockets twice before dawn as instruments aboard the nearby spacecraft recorded infrared, visible light and ultraviolet radiation from the fiery plumes.Data from the complex experiment is expected to help scientists with the Strategic Defense Initiative develop sensors capable of detecting enemy missiles against a variety of space backdrops, a critical element of the controversial defense scheme.

"To all of our expectations, the data we've seen . . . is spectacular, " said program director Howard Stears.

Discovery's seven-man crew planned to haul the SPAS-2 satellite back aboard late in the day for additional experiments.

The crew also was scheduled to look on as a small satellite, launched from Discovery Wednesday, released a small load of rocket fuel into space 107 miles away. Two more such satellites were scheduled for launch later in the day, and the astronauts will perform more experiments before returning to Earth Monday.

The rocket firings, a critical element of the Strategic Defense Initiative research flight, were delayed Wednesday by a glitch in orbit and human error on the ground that combined to prevent the Shuttle Pallet Satellite, or SPAS-2, from properly aiming its cameras and other instruments at Discovery.

But after a busy day of troubleshooting, the costly spacecraft's attitude control system was successfully reset and the 1-ton satellite was ready to photograph Discovery as the shuttle pinwheeled through space.