An advanced navigation satellite circled Earth Wednesday, boosted into orbit on the inaugural liftoff of the Delta 2, the first of the post-Challenger space rockets developed to launch vital military payloads.

"It was in every way a picture perfect launch," Air Force Lt. Col. Bob Tayloe, the launch director, said after Tuesday's successful liftoff.The Delta 2 is the first of at least 54 new unmanned rockets the Pentagon is ordering in a $14 billion program to launch much-needed reconnaissance, navigation, communications and other national security satellites.

About 40 of these payloads have been grounded for lack of a launch vehicle since the shuttle Challenger exploded three years ago, killing seven astronauts.

As a result of the accident, the Air Force decided it was a mistake to abandon unmanned rockets and to use the shuttle for sole access to space. It ordered three new rocket systems, the medium-size Delta 2 and Atlas 2 and the large, more powerful Titan 4.

The Delta 2 was the first to fly. On its debut, it carried into orbit the $65 million Navstar Global Positioning satellite, the first payload removed from the shuttle manifest to a throwaway rocket.

The satellite entered an initial elliptical orbit ranging from about 100 to 11,000 miles above Earth. On Thursday, an on-board motor will be fired to shift the satellite into a circular orbit of about 11,000 miles high.