A Delta Star missile-hunting satellite thundered into orbit Friday and quickly spotted a target as it began a key monthslong test to develop a split-second "Star Wars" defense against nuclear rockets.

The payload's sensors passed their first trial within two hours after launch when they successfully tracked the thrusting second stage of the Delta booster rocket after separation and during its fiery destruction in the atmosphere over the Indian Ocean."We watched that burn with the sensors; we not only got the second stage burning, but we also got the re-entry and breakup," Air Force Col. Michael Rendine, program manager for the Strategic Defense Initiative Office, told a news conference.

It was a good beginning for the $190 million mission.

Over the next several months Delta Star is to aim its sensors at a series of ground-based missile and space launches to help perfect the technology for detecting and destroying enemy boosters within minutes after they leave their launch pads.

Researchers especially want to gather rocket exhaust data against the background of the North Pole region - an area through which attacking Soviet missiles would travel.

Air Force officials said the Delta Star experiment is part of the research being done for the Strategic Defense Initiative, or Star Wars, program to develop a space-based missile defense system.

The launch was the third in a series. In a 1986 test, two satellites tracked each other and one destroyed the other by crashing into it. Last September, a satellite tracked 15 simulated nuclear missiles released by the same rocket in a test aimed at detecting missiles in midcourse flight after their motors have burned out.