then they need only a really large artificial satellite, and a man with a deep voice and a black cloak....

George wouldn't be bright enough

Have ion drives for maintaining position over target and standard chem drives for moving into position - will still have a limited shelf life but won't be as bad as current incarnations.

Bundle with it a measure for in-flight refuelling and you've got a long running spy bird.

No prob, whack a few positive electrons up close to light speed and they wont need any propelant. Or clone their bloody president and have all the propelant they could ever need in the form of high velocity bull$hit.

*Positive* electrons?

Sure.. you dont want any of the negative little buggers. Every man and his dog has them. ;)