The Problem of Space Debris

China's test adds to the perils for satellites.

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Last April, China was scheduled to host an international conference on minimizing debris in space. But three months earlier, China had destroyed its old Feng Yun 1-C weather satellite in an antisatellite weapon test that NASA called "the single worst contamination of low Earth orbit during the past 50 years." Unsurprisingly, the Chinese canceled the meeting.

When the Feng Yun exploded, tens of thousands of shards shot off in every direction. Today, the debris field extends from 125 miles above the surface of Earth to 2,500 miles. Air Force engineers have calculated that it will take a century for all the pieces to fall out of orbit.

"Instantaneous death." Many of the chunks are big enough to threaten satellites and equipment in lower Earth orbit, including the international space station. The Air Force Space Command has identified and is tracking 2,229 pieces of debris from the test that are at least as large as a softball. "Anything that size or larger, if it collided with a satellite, would equate to instantaneous death for a satellite," says Lt. Col. Michael Mason, who until recently ran the space surveillance network at the Joint Space Operations Center at Vandenberg Air Force Base. The center, which continues to find more Feng Yun remnants, saw a 20 percent jump—to 11,800—in the size of its catalog of space objects of concern, including satellites and debris, after the test. (In all, analysts track more than 17,300 objects in space, but the rest have yet to be identified with certainty.)

Chinese scientists told western counterparts that their calculations suggest the risk of collision has increased by less than 1 percent. But U.S. analysts have seen the number of close calls between satellites and debris more than double since the test. In an average week, Mason says, there will be up to 200 incidents where a piece of the Feng Yun passes within 3 miles of one of America's 400 satellites.

Indeed, NASA was forced to move its scientific satellite Terra on June 22 to avoid a chunk from the Feng Yun after engineers calculated that the risk of a collision was 7 in 100.

Similarly, Iridium, the commercial satellite voice and data communications firm, says the number of close calls between space debris and its 66 satellites rose 15 percent after the test, even though the overall risk of a collision is remote. Says John Campbell, executive vice president at Iridium, "We're concerned about any activity that makes space a less hospitable place to work in."