The first dozen or more Corona satellites and their launches were cloaked with disinformation as being part of a space technology development program called the Discoverer program. The first test launches for the Corona/Discoverer were carried out early in 1959. The capsule of Discoverer 2 might have been recovered by the Soviets, after landing on Spitsbergen Island. The first Corona launch containing a camera was carried out in June 1959 with the cover name Discoverer 4. This was a 750 kilogram satellite launched by a Thor-Agena rocket.
The return capsule of the Discoverer 13 mission, which launched August 10, 1960, was successfully recovered the next day. This was the first time that any object had been recovered successfully from orbit. After the mission of Discoverer 14, launch on August 18, 1960, its film bucket was successfully retrieved two days later by a C-119 Flying Boxcar transport plane. This was the first successful return of photographic film from orbit. In comparison, Sputnik 5 was launched into orbit on August 19, 1960, one day after the launch of Discoverer 14. Sputnik 5 was a biosatellite that took into orbit the two Soviet space dogs, Belka and Strelka, and then safely returned them to the Earth .
At least two launches of Discoverers were used to test satellites for the Missile Defense Alarm System (MIDAS), an early missile-launch-detection program that used infrared cameras to detect the heat signature of rockets launching to orbit.
The Corona film bucket was later adapted for the KH-7 GAMBIT satellite, which took higher resolution photos.
The last launch under the Discoverer cover name was Discoverer 38 on 26 February 1962. Its bucket was successfully recovered in midair during the 65th orbit (the 13th recovery of a bucket; the ninth one in midair). Following this last use of the Discoverer name, the remaining launches of Corona satellites were entirely top secret. The last Corona launch was on 1972-05-25. The project was abandoned after a Soviet Navy submarine was detected waiting beneath a Corona mid-air retrieval zone in the Pacific Ocean. The best sequence of Corona missions was from 1966 to 1971, when there were 32 consecutive successful missions, including film recoveries.
An alternative program to the Corona program was named SAMOS. This program included several types of satellite which used a different photographic method. This involved capturing an image on photographic film, developing the film on board the satellite and then scanning the image electronically. The image was then transmitted via telemetry to ground stations. The Samos E-1 and E-2 satellite programs used this system, but they were not able to take very many pictures and then relay them to the ground stations each day. Two later versions of the Samos program, such as the E-5 and the E-6, used the bucket-return approach, but neither of these programs carried out any successful missions.
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