Planetary defense shield
This defense shield is able to protect Earth from extra-terrestrial threats, including those posed by the Draconian Empire. The field can be adjusted, but is typically projected more than 100 miles above Earth's surface, but can be retracted to 100 miles in order for approaching ships to be investigated (BR25: Film, "Awakening").
A narrow channel within the shield is created for military use, allowing Thunderfighters and other crafts ingress and egress from Earth. Kane secretly plants a microtransmitter aboard William "Buck" Rogers's Ranger 3 on the belief that the Defense Directorate would escort him through this channel, which inevitably happens (BR25: Film, "Awakening").