太空垃圾数量已达“临界点”

The amount of debris orbiting the Earth has reached "a tipping point" for collisions, which would in turn generate more of the debris that threatens astronauts and satellites, according to a US study released on Thursday.

NASA needs a new strategic plan for mitigating the hazards posed by spent rocket bodies, discarded satellites and thousands of other pieces of junk flying around the planet at speeds of 17,500 miles (28,164 kilomtres) per hour, the National Research Council said in the study.

The council is one of the private, noNPRofit US national academies that provide expert advice on scientific problems.

Orbital debris poses a threat to the approximately 1,000 operational commercial, military and civilian satellites orbiting the Earth -- part of a global industry that generated $168 billion in revenues last year, Satellite Industry Association figures show.

The world's first space smashup occurred in 2009 when a working Iridium communications satellite and a non-operational Russian satellite collided 490 miles (789 km) over Siberia, generating thousands of new pieces of orbital debris.

The amount of orbital debris tracked by the US Space Surveillance Network jumped from 9,949 cataloged objects in December 2006 to 16,094 in July 2011, the National Research Council said.

The surveillance network tracks objects approximately 10 centimeters in diameter and larger.

Some computer models show the amount of orbital debris "has reached a tipping point, with enough currently in orbit to continually collide and create even more debris, raising the risk of spacecraft failures," the research council said in a statement released Thursday as part its 182-page report.

"The current space environment is growing increasingly hazardous to spacecraft and astronauts," Donald Kessler, the former head of NASA's Orbital Debris Program Office who chaired the study team, said in a statement.