The cause and consequences of a satellite fragmentation: A case study

Abstract

The fragmentation of a Pegasus Hydrazine Auxiliary Propulsion System upper stage on 3 June 1996 stands as the worst satellite breakup on record in terms of cataloged orbital debris. In addition to the more than 700 debris large enough to be tracked (approximately 10 cm in diameter or greater) in the 200 km by 2,000 km orbital regime by the U.S. Space Surveillance Network, a debris population of up to 300,000 objects larger than 4 mm appears to have been generated, based upon special radar observations. The debris cloud presented an immediate threat to many resident space objects, such as the Hubble Space Telescope, which resided in an orbit just 25 km below the breakup altitude. Special analyses were required to ensure the safety of the STS-82 Hubble Space Telescope servicing mission in February 1997. This paper describes the activities undertaken at the National Aeronautics and Space Administration Lyndon B. Johnson Space Center to characterize the near-term and far-term hazard of the debris cloud to manned and robotic spacecraft and to investigate the probable cause of the accident. The role of composite materials in the vehicle may have led to the creation of a much larger number of debris than would have been expected from a more conventional upper stage. To avoid a repetition of the incident, the Hydrazine Auxiliary Propulsion System upper stage was modified before its next launch, and additional passivation measures were adopted. This fragmentation event represents a textbook case for the hazards posed by satellite breakups and how fragmentation potential can be reduced without significantly affecting the capability of the vehicle.