A planetary shield (or defense grid) was a large scale deflector shield designed to protect an entire planet from bombardment, falling debris, or other hazards. The term planetary shield may also have been used for a large scale shield protecting a moon such as Nar Shaddaa.
The first deflector shields were developed to protect individual starships against various space hazards including attacks from other ships. The technology was later adapted for use aboard space stations, but the shields remained best suited to repelling starfighters.
Planetary shields could be scaled to cover bases, cities, or even entire planets. One of the two main types of planetary shields, encasing shields (like the second Death Star's), prohibited friendly fire from beneath the shield except through small gaps. Encasing shields could be curved to protect orbiting objects and seriously damaged the systems of craft that passed through them. The second type of planetary shield, a shutter shield, was more versatile in that segments could be moved to overlap others for increased defense, but shutter shields did less damage to craft passing through them and could not be oriented in a curve. The Rebel base on Hoth employed shutter shields. Both types of planetary shields fouled sensor scans. Pacifistic planets like Alderaan and Naboo, often relied on passive defenses like planetary shields instead of using more aggressive measures to ensure the populace's safety.
Battlestations such as Torpedo Spheres or Death Stars were designed to penetrate planetary shields. When such weapons were unavailable, planetary shields were often sabotaged as a prelude to either conquest (as in the conquest of Mon Calamari), or an orbital bombardment (as in the destruction of Caamas or the Second Battle of Bothawui).
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