" The main concern with satellites is space junk. More and more often, orbits have to be altered to avoid collisions with discarded rocket boosters, dead satellites, tools, etc. With nobody on the ground keeping track of orbital debris and altering trajectories, low earth orbit will rapidly become a dangerous place.

A screw moving at 17,500 miles per hour has roughly the same kinetic energy as a car doing highway speed, and one satellite can shatter into a lot of pieces, each with the same destructive potential. Without a lot of manpower on the ground, a cascade reaction is inevitable."

"are satellites strong enough to survive re-entry?"