[ricksunny]

Brilliant. As a result I'm reading up on graveyard orbits and end-of-life perturbations from various celestial sources. Also, this gem, whose longitude values roughly correspond to what I'm seeing:

last line of: https://en.wikipedia.org/wiki/Geosynchronous_orbit#Geostatio... :

"Geostationary satellites will also tend to drift around one of two stable longitudes of 75° and 255° without station keeping.[21]"

It cites SMAD, which on its face is more than good enough for me, but since I don't have a copy handy, it would still be interesting to know why those meridians would represent particularly attractive ones to drift into.

[cfraenkel]

*Dead* satellites are supposed to be boosted into a graveyard orbit so they don't clutter up the neighbourhood for everyone else. Of course if it just fails, and can't be commanded there's not much anyone can do, but that's relatively rare. Most will be drifting at a pretty good clip, +100 km or more above geosynch.