The launch was postponed for at least two days because of trouble with an electronic box aboard the unmanned Delta rocket, part of the safety system for destroying the vehicle if it flies off course.

Once in orbit, NASA's Swift spacecraft will swivel quickly to detect gamma ray bursts in the universe, which scientists believe represent the creation of black holes. Black holes are believed to be the invisible remains of collapsed stars; black holes' gravitational pull is so great that not even light can escape from one.

Besides NASA, the Italian Space Agency and Britain's particle physics and astronomy research council are taking part in the $250 million mission.