Random conversation in Matt McGrath’s office a couple years ago after reading Nick Chrisman’s book we all knew

First CORONA satellite launch (military reconnaissance) as part of Discoverer 4

• First CORONA satellite launch (military reconnaissance) as part of Discoverer 4

• Carried ~10km of 70mm panchromatic film
• ~10m resolution (improved to 2m by 1972)
• Returned film canisters to Earth in capsules, which were recovered in mid-air by C-119
• Images used for base maps due to once a month capsule returns
• 144 Corona satellites
• USAF/CIA program - 1959-1972
• Secret until 1992

Large grid of 281 survey markers visible from space placed in Arizona desert in a 1 mile offset pattern

• Large grid of 281 survey markers visible from space placed in Arizona desert in a 1 mile offset pattern

• Used to measure resolution and calibrate the orbiting camera
• Markers are 50 feet in diameter and resemble Maltese cross
• At the center of each cross was a saucer-sized brass disk stamped Corps of Engineers/U.S. Army Map Service
• Resolution measured by examining the resolution test target on the ground in the clean low distortion air of Arizona
• Markers still visible in Bing Maps and Google Earth