Orbital litterbugs
Posted: Friday, February 02, 2007 7:40 PM by Alan Boyle
As experts track more and more of the debris created by last month's Chinese anti-satellite test, they have determined that the incident will likely rank as the world's biggest case of space littering. Every day they're spotting additional pieces of the broken-apart weather satellite, which Beijing shot down Jan. 11 with one of its own ground-based missiles.
NASA and the North American Aerospace Defense Command, or NORAD, have been updating their list of orbiting space junk on a daily basis. Last week I wrote about an online video from the Center for Space Standards and Innovation that showed 33 pieces of debris circling the globe. Today the center's technical program manager, T.S. Kelso, gave me an e-mail update:
"As of this morning, NORAD is reporting 597 pieces of debris associated with this event. At this point, we only have data for 552 pieces, but I would expect to see the rest of this data within the next day or so. I will update graphics on CelesTrak to reflect the new data as soon as I get back from going to talk to the folks at Air Force Space Command on this topic.
"In the larger scheme of things, this event is now the second-largest debris-generating event on record. The largest is still the STEP 2 rocket body event on 1996 June 3, which generated 709 pieces of debris. The next largest event was the event resulting from the explosion of an Ariane 1 final stage on 1986 November 13, which generated 489 pieces of debris. This event, at present, represents the largest cloud of debris on orbit, with the next largest cloud only containing about 250 pieces of debris. All of this information comes from the NASA Orbital Debris Program Office in the report 'History of On-Orbit Satellite Fragmentations.'
"Finally, to put the overall risk in some perspective, of the 3,150 payloads in Earth orbit or beyond, we have orbital data for 2,782 of those. Of the missing 368 payloads, some are in deep-space orbits around the sun or other planets, and some are not released by the US government for whatever reason. Of the 2,782 payloads we do have data for, 1,860 payloads pass through the regime now affected by the debris from the Chinese ASAT test."
Be sure to check out the center's Web page on the anti-satellite test for the latest data and the grooviest video visualization of the orbiting debris cloud.
Meanwhile, Space.com's Leonard David quotes NASA officials as saying the debris count was likely to surpass the 900 mark, due to the addition of about 300 objects that are being tracked but have not yet been cataloged. "These will be cataloged in due course," said Nicholas Johnson, chief scientist for orbital debris at NASA's Johnson Space Center.
What's more, NASA estimates that the Chinese test created another 35,000 bits too small to be tracked, in the range of a half-inch to 4 inches (1 to 10 centimeters) in diameter. The threat to the international space station peaked shortly after the Jan. 11 shootdown and is now declining toward background levels, but the long-lived debris cloud could conceivably threaten other satellites.
With the benefit of weeks of observation, Johnson ranked the incident as "the most prolific and serious fragmentation in the course of 50 years of space operations." And that's just one shootdown of a measly weather satellite. Imagine what might happen if someone decided to go after an entire fleet of spy satellites.
