dumb-arsed question but can we quickly get it out the way; assuming I’m thinking right, not possible to redirect an exisisting satellite using it’s, erm, ‘booster’ engines? Or something …
You can redirect a satellite to some extent with engines. You can’t usually radically change its orbit, but you should be able to do enough to turn a hit into a miss, if you have enough warning and know exactly where the impactor is going to be. I don’t think that the ISS actually has any engines on board, though: It needs to dock with some other vehicle to boost its orbit.
The Zvezda module on the ISS provides some small amount of divert and attitude control capability sufficient to dodge orbital “junk”, which it in fact just did yesterday. It doesn’t provide enough delivered impulse for major orbit-raising maneuvers or to dodge widely dispersed clouds of debris, however. Satellites in MEO or GEO/GSO are generally required to have a propulsion system sufficient to move the spacecraft into a retirement orbit at the end of operational life so that it doesn’t pose a hazard to other spacecraft; surveillance satellites often have propulsion systems with considerable total impulse in to permit periodic changes in orbit throughout life to change times and areas of surveillance coverage. Most satellites in LEO have minimal or no propulsion other than a small. ACS system (if that) with the assumption that the orbit will naturally decay after end of operational life.
Stranger
Stranger, in another thread (this one) I ask if it is possible to steal a satellite by filching the encryption keys.