Tech & Biz

ISS dodges debris

by mchawk | August 29, 2008 at 03:32 pm

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The International Space Station has had to perform an evasive manoeuvre to avoid colliding with debris from a Russian satellite that broke-up earlier in the year. NASA reports:

Using ATV thrusters, the ISS performed a 1 m/s braking burn yesterday at 12:11pm EDT to remove the risk of collision with an orbital object - #33246 (part of the Kosmos-2421 satellite). The retrograde firing of 5 min 2 sec duration resulted in a mean altitude loss of ~1.77 km.

A few things about this maneuver are interesting. First, this is the first time in five years that the ISS has had to perform a debris avoidance maneuver. Second, the maneuver was unusual in that was a retrograde maneuver, which slows the ISS and brings it to a lower orbit instead of higher. The last time a retrograde maneuver was performed was eight years ago. Third... the Russians deny that the satellite has broken up. Fourth, however, the Mission Control Center in Moscow carried out the maneuver.

Even thought the NASA report clearly names the origin of the debris, Russian news is reporting the manoeuvre was to avoid "pieces of space debris" and the European Space Agency merely referred to it as coming "from an old satellite."

Launched in June 2006, the Cosmos-2421 was a naval surveillance satellite, designed for electronic eavesdropping to keep track of Western military vessels. According to U.S. tracking data, the satellite disintegrated on March 14 into hundreds of pieces — with further fragmentation on April 28 and June 9. More than 500 objects resulted, creating one of the largest debris clouds in space history.

This type of Russian satellite has been observed to do this before, satellite watcher Jonathan McDowell told NPR in July. Because the initial breakup usually occurs within range of Russian space tracking stations, experts suspect that the Russians issue some sort of self-destruct command after the satellite's orbital mission ends.

Russian space officials have repeatedly denied that any explosion occurred.

Once the debris avoidance maneuver was completed, the ISS was turned back to its original orbital attitude, but it is still very much in the firing-line, with more debris heading its way.

A second possible conjunction with another piece (#33248) of Kosmos-2421 has been identified for tomorrow (8/29) at 9:09pm EDT... This would require another DAM (Debris Avoidance Maneuver), but more tracking is required for a burn decision. Estimated prime TIG (Time of Ignition): tomorrow 7:00pm.