02.13.09

The mystery deepens over the Iridium collision

Posted in Iridium at 11:13 am by timfarrar

Our initial reaction to the collision of Iridium SV33 with a non-functioning Russian Cosmos 2251 satellite was that NORAD (or rather the US Strategic Command or Stratcom to give it the current title) would have questions to answer about why it did not warn of the danger of a possible collision. Its now been pointed out to us that both Iridium and Stratcom would have been running their own collision prediction software, not least because Iridium has to be careful that its own satellites do not collide with one another, though the input data is supplied in a USSC database (and is publicly available at Heavens Above).

However, it appears that the data did not show any predicted collision between the two satellites and they were expected to miss one another by 80km or so. Either something happened to the Russian satellite to dramatically increase its drag (“a bit falling off”?) or the Iridium satellite was moved (which appears implausible since it was in service at the time and has to stay within a box of a few km to keep its crosslinks in contact with the rest of the constellation).

Hopefully a better explanation will emerge soon, but this highlights why Iridium didn’t identify the Russian satellite correctly at first and was taken by surprise by the collision. In the meantime, we’re sure this will give ammunition to conspiracy theorists, speculating about Russia deliberately trying to take out an American satellite. However, that would undoubtedly be going too far – as the US Missile Defense Agency knows only too well, its pretty hard to hit such a small target, and no-one has actually suggested that the Russian satellite was secretly under control.

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