Isegoria

Modern meteorology was born 60 years ago, with the launch of the Television InfraRed Observation Satellite, or TIROS-1:

During its 78 days of operation, TIROS-1 successfully monitored Earth’s cloud cover and weather patterns from space.

This was a potent moment for the field of meteorology. For the first time, scientists were able to combine space-based observations with physical models of the atmosphere that were just beginning to be run on supercomputers.

After World War II, mathematician John von Neumann led development of a computer to crunch through a set of equations put together by Jule Charney and other scientists. By the mid-1950s, Charney’s group began to produce numerical forecasts on a regular basis.

All of a sudden, meteorologists had two incredibly useful tools at their hands. Of course, it would take time for more powerful computers to produce higher-resolution forecasts, and the sensor technology launched on satellites would require decades to improve to the point where spacecraft could collect data for temperature, moisture, and other environmental variables at various levels in the atmosphere.

But by around 1980, the tools of satellite observations and numerical models that could process that data started to mature. Scientists had global satellite coverage, 24 hours a day, and forecasts began to improve dramatically. Today, the fifth day of a five-day forecast on the app on your phone is about as accurate as the next day’s forecast was in 1980.

I had always assumed that spy satellites used TV cameras, but the first spy satellites used film:

The Corona satellites used special 70 millimeter film with a 24-inch (610 mm) focal length camera.[7] Manufactured by Eastman Kodak, the film was initially 0.0003 inches (7.6 ?m) thick, with a resolution of 170 lines per 0.04 inches (1.0 mm) of film.[8][9] The contrast was 2-to-1.[8] (By comparison, the best aerial photography film produced in World War II could produce just 50 lines per mm (1250 per inch) of film.)[8] The acetate-based film was later replaced with a polyester-based film stock that was more durable in Earth orbit.[10] The amount of film carried by the satellites varied over time. Initially, each satellite carried 8,000 feet (2,400 m) of film for each camera, for a total of 16,000 feet (4,900 m) of film.[8] But a reduction in the thickness of the film stock allowed more film to be carried.[10] In the fifth generation, the amount of film carried was doubled to 16,000 feet (4,900 m) of film for each camera for a total of 32,000 feet (9,800 m) of film. This was accomplished by a reduction in film thickness and with additional film capsules.[11] Most of the film shot was black and white. Infrared film was used on mission 1104, and color film on missions 1105 and 1008. Color film proved to have lower resolution, and so was never used again.[12]

The cameras were manufactured by the Itek Corporation.[13] A 12-inch (30 cm), f/5 triplet lens was designed for the cameras.[14] Each lens was 7 inches (18 cm) in diameter.[8] They were quite similar to the Tessar lenses developed in Germany by Zeiss.[15] The cameras themselves were initially 5 feet (1.5 m) long, but later extended to 9 feet (2.7 m) in length.[16] Beginning with the KH-4 satellites, these lenses were replaced with Petzval f/3.5 lens.[12] The lenses were panoramic, and moved through a 70° arc perpendicular to the direction of the orbit.[8] A panoramic lens was chosen because it could obtain a wider image. Although the best resolution was only obtained in the center of the image, this could be overcome by having the camera sweep automatically (“reciprocate”) back and forth across 70° of arc.[17] The lens on the camera was constantly rotating, to counteract the blurring effect of the satellite moving over the planet.[12]

The first Corona satellites had a single camera, but a two-camera system was quickly implemented.[18] The front camera was tilted 15° aft, and the rear camera tilted 15° forward, so that a stereoscopic image could be obtained.[8] Later in the program, the satellite employed three cameras.[18] The third camera was employed to take “index” photographs of the objects being stereographically filmed.[19] The J-3 camera system, first deployed in 1967, placed the camera in a drum. This “rotator camera” (or drum) moved back and forth, eliminating the need to move the camera itself on a reciprocating mechanism.[20] The drum permitted the use of up to two filters and as many as four different exposure slits, greatly improving the variability of images that Corona could take.[21] The first cameras could resolve images on the ground down to 40 feet (12 m) in diameter. Improvements in the imaging system were rapid, and the KH-3 missions could see objects 10 feet (3.0 m) in diameter. Later missions would be able to resolve objects just 5 feet (1.5 m) in diameter.[22] A single mission was completed with a 1 foot (0.30 m) resolution but the limited field of view was determined to be detrimental to the mission.[citation needed] 3 feet (0.91 m) resolution was found to be the optimum resolution for quality of image and field of view.

[...]

Film was retrieved from orbit via a reentry capsule (nicknamed “film bucket”), designed by General Electric, which separated from the satellite and fell to Earth.[30] After the fierce heat of reentry was over, the heat shield surrounding the vehicle was jettisoned at 60,000 feet (18 km) and parachutes deployed.[31] The capsule was intended to be caught in mid-air by a passing airplane[32] towing an airborne claw which would then winch it aboard, or it could land at sea.[33] A salt plug in the base would dissolve after two days, allowing the capsule to sink if it was not picked up by the United States Navy.[34] After Reuters reported on a reentry vehicle’s accidental landing and discovery by Venezuelan farmers in mid-1964, capsules were no longer labeled “SECRET” but offered a reward in eight languages for their return to the United States.[35] Beginning with flight number 69, a two-capsule system was employed.[24] This also allowed the satellite to go into passive (or “zombie”) mode, shutting down for as many as 21 days before taking images again.[11] Beginning in 1963, another improvement was “Lifeboat”, a battery-powered system that allowed for ejection and recovery of the capsule in case power failed.[36][37] The film was processed at Eastman Kodak’s Hawkeye facility in Rochester, New York.[38]

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