A Security Satellite was an artificial satellite that could be found in various space sectors. They had a holo-net relay and would guard Nefarious's ships to attack any intruders (i.e. Aphelion). They could be destroyed easily, but had to be destroyed as soon as possible to avoid attention. Whenever Ratchet neared it, it released a signal to nearby ships, actived a shield (Requires x number of ships destroyed to disable the shield so that he could destroy the satellite), and emitted an alert message.
Behind the scenes
In concept art images of Ratchet & Clank Future: A Crack in Time, the security satellite is known as Nefarious Spy Satellite. 
- Ratchet & Clank Future: A Crack in Time (first appearance)