Feb 2009

Iridium + Cosmos =

On February 10th, an active Iridium satellite and a defunct Cosmos satellite ran into each other in orbit while over polar Russia. The impact of the collision of these two large satellites dispersed their remaining fragments into two clouds of orbiting objects. Each cloud of dispersing remnants spread out and, as they spread apart, NORAD was able to track them and to begin to release orbital elements for the largest of them (as time passes more and more will be cataloged -- at the altitude in question NORAD catalogs all objects larger than a grapefruit).

By February 20th, NORAD had released orbital elements for 85 Cosmos fragments and 48 Iridium fragments. Telling our nifty satellite tracker to show all 133 of these objects as they were this morning reveals them spread out in two trains circling the earth:

Just to be cute, I sent time in reverse and ran all these objects back to that moment on February 10th to see what the clusters looked like. Ideally, they would appear as two solid clumps when they passed through each other, but (a) the algorithms used drift a little after ten days and (b) the data from Feb 20 describes objects which have already started to decay in their own right so they wouldn’t be expected to pass through the original point of impact when tracking them back to that time. Here’s the result:


The left screenshot shows the slightly extended clumps over Siberia (enlarged on the right). The left shot also shows a couple of other objects to the north of the impact location -- these might be objects related to the Iridium satellite but not the result of the collision.

PS: By mid-day Feb 21, there were 144 Cosmos and 68 Iridium fragments in NORAD’s database.

Change of pace ...

Well, I was beaten to the post by folks in Vancouver with GoSatWatch.

They have a nice iPhone application which does all that I was planning to do, and that’s taken some of the wind out of my sails. However, their approach is a little different than mine and I’m going to press on with a version of my application for the App Store.