First optical-imaging spy satellite
Corona C-9
first first
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The first optical spy satellite was CORONA C-9 (aka Discoverer 14), which was jointly operated by the United States Air Force and the Central Intelligence Agency. This satellite was launched on 18 August 1960 and its film capsule was recovered on 16 September.

The CORONA satellite reconnaissance program was approved by President Dwight D. Eisenhower in February 1958, just four months after the launch of the first aritificial satellite, the Soviet Union's Sputnik 1. The US Air Force had been exploring the idea of satellite reconnaissance since 1956, but problems with the development of a US launch vehicle had put any practical tests on hold. For Corona, overall management of the project was shifted to the CIA's Directorate of Science & Technology, although the US Air Force was still responsible for the launch vehicles and practical operation of the satellites.

Building a photo reconnaissance satellite was an enormous technical challenge. Only a few weeks had passed since the United States launched its first crude satellite, Explorer 1, but now the CIA's engineers were being asked to design a satellite that could operate in a polar orbit, maintain stability over all three axes and deorbit on command.

Furthermore, this was before the invention of the CCD (the light sensor used in digital cameras), so the pictures would have to be taken with film cameras and that film would then have to be returned to Earth. The final design saw the film loaded into jettisonable capsules that would re-enter and then descend with a parachute. Before the capsule fell into the sea, it would be caught in mid-air by a US Air Force plane fitting with a special "skyhook" attachment.

By 1959, the first test flights were ready to begin. The public name for the project was Discoverer, and each launch was given a Discoverer-program designation and a civilian cover mission (usually "studying propulsion, communication, recovery techniques and cosmic radiation"). Despite these measures, it seems to have been generally understood that these flights were at least related to espionage, if not actively engaged in it.

Discoverer 1 (launch on 28 Feb 1959) was a success, with the satellite becoming the first to be placed into a polar orbit. Discoverer 2 (13 April 1959) was also promising, with a successful test of the stabilisation system and deployment of a dummy film capsule. The attempt to recover the capsule failed, however. After this the program suffered repeated setbacks, with 10 unsuccessful missions in a row (satellites were sent into the wrong orbits, stabilisation systems failed, rockets cut off early or simply exploded on the launch pad).

It was not until Discoverer 13, launched on 10 August 1960, that the whole system worked as designed, although that mission didn't carry an active camera system. The first real payload of reconnaissance imagery was recovered on 16 September 1960 by a C-119J "flying boxcar" flown by Captain Harold Mitchell.

The Corona program would go on to run for another decade. The cameras were upgraded several times, but it remained a film-based system until the program's termination in 1972. In total, 144 Corona missions were flown, of which 113 were successful.