Feb 18, 2013
The meteorite that exploded over Chelyabinsk on February 15, 2013, was a pretty big thing – NASA estimated  that it was about 15-17 meters in size and weighed 7-10 thousand tonnes. Surely it should have been detected by someone. Quite a few commentators in Russia indeed asked why the country needs all these early-warning radars if they could not detect something that large and threatening – it’s worth keeping in mind that the explosion that accompanied disintegration of the meteorite was equivalent to about 500 kt.
As far as I can tell, the early-warning radars never had a chance, but it wasn’t their fault – the problem was that they were never supposed to detect objects that are coming from outer space. The picture above shows the estimated trajectory of the meteorite and fans of the Daryal radar in Pechora and Dnepr in Mishelevka. The fan of the Don-2N radar of the Moscow missile defense system can be seen as well (for other radars, see this post ). It’s better to see this in Goolge Earth – here is the kmz file .
I assumed for simplicity that the meteorite flew along a straight line – that’s not quite correct, but should work for the purposes of this analysis. The AGI simulation  of the trajectory based on the Meteosat-9 data shows that the meteorite came from the azimuth of about 60 degrees (they got the meteorite path wrong, in fact – it passed to the south of Chelyabinsk, not to the north).A different estimate  suggests that the azimuth could be about 100 degrees, but that doesn’t matter much in the end. The re-entry angle is taken to be about 15 degrees – this is what various photos show.