WASHINGTON -- A team investigating the April malfunction of an Air Force Titan IV rocket upper stage is "wrapping up" its accident review and plans to release a final report "within weeks," according to the Air Force Space Command in Colorado Springs, Colorado. Capt. Lewonnie Belcher tells space.com that the group focused only on the fate of the Defense Support Program 19 satellite, which was marooned in the wrong orbit when the stage, called an Inertial Upper Stage (IUS), malfunctioned. The failure converted the multi-million dollar space vehicle attached to the stage into worthless space junk. The successful launch of NASAs Chandra x-ray telescope, which used an identical IUS rocket on Fridays deployment from the Space Shuttle Columbia, didnt effect the investigation or the movement to clear the IUS/Titan IV combination to flight again, Belcher said. IUS rockets are built by the Boeing Company for Lockheed Martins Titan IV fleet. The unit has also flown aboard the NASA Shuttles since 1982.

The Air Force team investigating the incident has determined that the first of the two stages of the IUS failed to drop away when the second stage ignited. The added weight of the spent stage caused the second stage and the attached satellite to tumble out of control. The struggling second stage motor still fired, but the resulting orbit was the wrong one for the Defense Support Program. While the cause has been identified, the reason the stage failed to separate isnt yet clear, although sources tell space.com that human error during the stages assembly and checkout is the most likely reason. DSP satellites, built by TRW, Inc. in Sunnyvale, California are used to warn the Pentagon in the event of a missile launch anywhere in the world.

The U.S. launch industry breathed a sigh of relief Friday when the identical IUS unit powering Chandra worked perfectly. Both of the rocket stages fired and dropped away as planned. The industry has suffered six failures during the past year, and the IUS/Titan IV combination is a workhorse booster for the U.S. militarys satellites and other classified spacecraft missions.