Yep, that's a very interesting Wikipedia article. One thing that surprised me is that most of the needles reentered within 3 years. They have a pretty large su

Yep, that's a very interesting Wikipedia article. One thing that surprised me is that most of the needles reentered within 3 years. They have a pretty large surface area per unit mass, so the effects of the very thin atmosphere up there is maximized. Normally a satellite at 3,500 km would take centuries to decay. There are some clumps of needles still up there. One not-well-understood thing is how many small clumps remain -- the clumps which are too small to be seen on radar.