HYDERABAD, India — One of the world’s leading experts on space debris warned Sept. 27

that it is only a matter of time before a fragment from China’s intentional destruction of its Fengyun 1C satellite Jan. 11 collides with another satellite.

“I cannot say when, but it will definitely happen,” Nicholas Johnson, NASA’s chief scientist for orbital debris, told Space News


the 58th

International Astronautical Congress that opened here Sept. 24.

“In terms of catalogued debris this event has constituted the worst single fragmentation in the history of the space age and its effects will be very long lived,” Johnson said. “The Chinese, who never reacted to the international concern, now understand the consequences of their action and hopefully it will not be repeated.”

More than 2,000 pieces of Fengyun 1C debris,

1 centimeter or greater in size, have been identified by the U.S. space surveillance network, Johnson said. This represented a sudden increase of more than one-third in the cataloged debris


low Earth orbit. The largest fragment seen was about

2 square meters


NASA recently

had to maneuver its Terra Earth observing satellite to avoid the

debris, which also came close to the international space station, Johnson said.

Fengyun 1C, an aging weather satellite, was destroyed by a medium-range Chinese missile that slammed into the spacecraft at an altitude of about 865 kilometers.

Johnson said some of the debris located around that altitude

will come down at a faster rate at the beginning of the 11-year solar cycle, or around 2011, due to anticipated increased solar flare activity