U.S. and China face mounting orbital debris hazards
BY CRAIG COVAULT
Posted: November 18, 2009
Quick-thinking Chinese ground controllers were able to maneuver a high-value Chinese spacecraft out of the path of space debris marking the first such save by China, demonstrating the country's maturing space tracking and command and control systems.
The event started late Oct. 1, when Chinese tracking data indicated that a risk of collision existed between the debris and an operational satellite, which the Chinese declined to identify.
China's land and sea based tracking network found that space debris could pass dangerously close to the Chinese spacecraft. Data showed the debris could pass at least 200 meters or closer to the Chinese satellite with a strong chance it could actually collide.
CASC immediately contacted the satellite designers Zhu Hongchang and Yu Weimin to start contingency planning.
Satellite Tracking, Telemetry and Control Centers in Xi'an and Beijing coordinated with the satellite manufacturer, and CASC activated the satellite's orbital maneuvering system to prepare for the moment best suited for an avoidance maneuver.
The Chinese said activities performed quickly on an emergency basis included:
Analysis indicates that a warning level of 10, the worst case, was in effect as the debris approached. But by the time the event occurred, the risk had dropped to a minus 7, a safe level.
In the U.S., major efforts are also underway to improve and exercise debris see-and-avoid measures.
The U.S. military says it is now tracking 800 maneuverable satellites for possible collisions and expects to add 500 more non-maneuvering satellites by early 2010.
The U.S. Air Force began upgrading its ability to predict possible collisions in space after a dead Russian military communications satellite and a commercial U.S. satellite owned by Iridium collided on Feb. 10.
General Kevin Chilton, commander of U.S. Strategic Command, called the collision the "seminal event" in the satellite industry during the past year and said it destroyed any sense that space was so vast that collisions were highly improbable.
He said military officials had wanted to do more thorough analysis of possible collisions in space, but had lacked the resources. Before the collision, he said they were tracking less than 100 satellites a day. "It's amazing what one collision will do to the resource spigot," he told a space conference in Omaha, Nebraska.
The crash, which was not predicted by the U.S. military or private tracking groups, underscored the vulnerability of U.S. satellites, which are used for a huge array of military and civilian purposes.
Chilton said the Air Force was tracking more than 20,000 satellites, spent rocket stages and other objects in space, up from just 14,000 a few years ago. But he said that was just what U.S. could "see" and there were estimates that the actual number was much greater, posing a potential threat to satellites on orbit.
Air Force Lieutenant General Larry James, who heads U.S. Strategic Command's Joint Functional Component Command for Space, told journalists at the space conference in Omaha that the Air Force met its goal for tracking possible collisions among 800 satellites that have the ability to be moved in September -- ahead of an October target date.
"Our goal now is to do that conjunction assessment for all active satellites ... roughly around 1,300 satellites ... by the end of the year and provide that information to users as required," he says.
Some of the 500 satellites still to be assessed cannot be shifted because they do not carry extra fuel that would be needed to move them once in orbit.
To increase its ability to predict possible collisions, the Air Force has been buying more computers and hiring analysts. It also works with commercial satellite operators to share data collected by their spacecraft and by U.S. government sources.
Chilton lauded the efforts, but said the work was still too reliant on Air Force analysts and needed further improvement. "We are decades behind where we should be," he said.
Victoria Samson, with the nonprofit Center for Defense Information, said the Air Force needed more trained operators to do the analyses and the goal of adding 500 more satellites to the analysis might be "optimistic."