There are different security measures that have been put in place by different countries to ensure the safety of satellites from terrorists. These measures remain a secret to the great masses. However, with daily advancement in technology, there is always a constant threat to the satellite security.
Yes, height. The terrorists' RPGs can't reach the satellites orbiting the earth at 200 miles up. I think they should try it though, and prove their belief in allah, fire their RPG straight up into the air and see if allah will guide them to their targets ... insha'allah!