A planetary shield is a large scale shield emanated by a Shield Base, designed to protect an entire planet from bombardment, falling debris, cosmic radiation, or other hazards. The term planetary shield may also be used for a large scale shield protecting a moon.
The first shield systems were developed to protect individual starships against various space hazards including micrometeorites and attacks from other ships. The technology was later adapted for use aboard space stations.
Planetary shields can be scaled to cover bases, cities, or even entire planets. One of the two main types of planetary shields, encasing shields, prohibit friendly fire from beneath the shield except through small gaps. Encasing shields can be curved to protect orbiting objects and seriously damage the systems of any craft that pass through them. The second type of planetary shield, a shutter shield, is more versatile in that segments can be moved to overlap others for increased defense, but shutter shields do less damage to craft passing through them and cannot be oriented in a curve. Both types of planetary shields can foul sensor scans.