Satellites: 80/100/120kt.
Weapons Platforms: 200/400/600kt.
You don't understand the difference between something smaller than an escort and something as large as a battle cruiser? All satellites are smaller than the smallest ship. It's hard to cram a decent set of components into them. Weapons platforms start at Frigate size and go on up. A medium or large weapons platform can fend off battleships.
You might be thinking that you can just dumps LOTS of satellites to create the same level of benefit, but it ain't so. Each sat needs a computer core, each sat needs combat sensors and/or ecm, each sat needs shields and/or armor. But each sat is much smaller than a weapons platform. The amount of firepower you can put in space with satellites is MUCH less per ton than weapons platforms. Then there are differences in how they perform in combat.
Satellite Groups are placed randomly around a planet when combat begins. If the enemy comes from a direction other than the direction in which the satellites are placed, they can just shoot the planet without having to fight your satellites. Not only can't they "bypass" weapons platforms, but weapons platforms have to be destroyed BEFORE the planet they protect can be damaged. They function as "armor" for your planet as well as weapons systems.
Also, they are NOT visible from a distance. An enemy can SEE how many satellites, bases, or ships your planet has just by being in the same system. This let's them plan their attack better. Unless they've used intelligence means (Covert Recon) they cannot know how many weapons platforms are on your planet, though they can make a rough guess at how many their COULD be based on its size. This makes planning for the attack more difficult. They will have to commit more resources to be sure of winning.
Beginning to see some of the reasons why weapons platforms are useful?
[This message has been edited by Baron Munchausen (edited 26 August 2000).]