[Comar]

Weapon platforms are planet based and used for planetary protection. Satellites can be placed anywhere, but ususally seen around planets or jump points. Bases are used to protect planets or as orbital shipyards.

The best protection for a planet is a powerful and active fleet ( hear that, NASA???? ). You can also heavily mine jump points which will add a lot of protection.
Last is the close in defenses ( weapon platforms, orbital bases and satellites ).