Sol Station and Earth's planetary shields under fire in 2401
Earth's shield raised in 3189
A planetary shield was a deflector shield that enveloped an entire planet, preventing unauthorized access and orbital bombardment.
Aldea was equipped with an electromagnetic shield and cloaking device, which also caused damage to the planet's ozone layer. In 2364, Lieutenant Commander Data found random fluctuations within the shield that weakened isolated regions of its structure, allowing an USS Enterprise away team to transport through and disable its power source. (TNG: "When The Bough Breaks")
The Kraylor homeworld was protected by a shield grid, which kept the Kraylor's enemies, the Annari, from attacking it directly. (VOY: "Nightingale")
Vashti's security net in 2385
A standard Romulan planetary defense system, such as the one installed on Vashti, consisted of a network of orbital killer drones that generated an impenetrable security net around the planet. (PIC: "Absolute Candor")
During the attack on Mars in 2385, compromised synths dropped the planetary defense shields around Mars before destroying the Utopia Planitia Fleet Yards. (PIC: "Remembrance")
By the 25th century, Earth was equipped with a planetary shield, which was linked to Sol Station. In 2401, the planetary shields fell when the station was overwhelmed by an assault from a Borg-controlled Federation fleet. (PIC: "The Last Generation")
In the 32nd century, Earth was protected by shields generated by a network of orbital force field generators. In 3190, the shields were partially dismantled by debris propelled toward the planet by the Dark Matter Anomaly. (PIC: "People of Earth", "Coming Home")