Here's how they "downloaded" back then... According to documents released by the NRO, each HEXAGON satellite mission lasted about 124 days, with the satellite

Here's how they "downloaded" back then... According to documents released by the NRO, each HEXAGON satellite mission lasted about 124 days, with the satellite launching four film return capsules that could send its photos back to Earth. An aircraft would catch the return capsule in mid-air by snagging its parachute following the canister's re-entry.