back high-res images of almost anywhere on earth to secret government

intelligence agencies but now that same technology is also available for all of

us with things like Google Earth however when the very first surveillance

satellites were launched things were really quite a lot more primitive and

you could forget about electronically beaming images back to earth so how did

they get the images back and how did this affect missions like Apollo.

In the Cold War era one of the biggest problems for the US and the West in

general was just not knowing what was going on in the Soviet Union and to a

similar extent Communist China not for nothing did Churchill say that and Iron

Curtain has descended across Europe. In World War two

the Allies relied upon airborne reconnaissance to see what the Germans

were up to and many of the secret weapons like the v2 rocket and a v1

flying bomb were uncovered by aerial photos but Western Europe is small in

comparison to the Soviet Union you could drop it in the middle of a Soviet Union

and not know it was there at all. Although the U.S. started aerial

reconnaissance along the Soviet borders in 1946, it was the start of a Korean War

in 1950 which brought home the need for more information on the Soviet Air

Force and its capabilities and if it could mount a surprise bomber attack

with nuclear weapons on the US. High-altitude overflights were gradually

built up first with a Boeing B-47 a predecessor to the B-52 and later with

the lockheed U-2 spy plane there had also been other aerial surveillance

methods like project gen tricks which used helium balloons to carry cameras at

heights of up to a 100,000 feet and blown by the westerly winds across

the Soviet Union China but only around 6% of these were recovered with usable

images, the rest were either shot down or blown off-course. Clearly a better safer

method was needed and quickly. In 1960 Gary Powers U-2 spy plane was shot down

over the Soviet Union causing a major diplomatic incident and forcing the U.S.

to suspend over flights but the problem had also been anticipated. The CIA who

also ran the U-2 spy planes headed up a project called Corona and have been

working on put in a camera into a satellite in a low Earth orbit 160

kilometers above the earth there it would be safe from any Soviet defences

and of a speed at which it traveled some 27,000 km/h they could image huge

tracts of land in a very short space of time. The problem with putting a camera

in space was up until then no one had actually launched something into orbit

and then safely recovered it back to earth. Now you may well ask why didn't

they just use video cameras and beam the images back but that kind of technology

just wasn't ready and it wouldn't be until the late 1970s almost 20 years

later before high-resolution digital imagery would be good enough for

intelligence gathering. So the idea they came up with was to

drop the exposed film from orbit in a heat shield his bucket back to earth

over the Pacific Ocean and then catch its parachute over planes at about

15,000 feet. Now it might sound like a crazy idea but catching it with a plane

was actually the easy part and they've done it before with the Genetrix

surveillance balloons, the difficult part was getting the film bucket to be in the

same area as the waiting planes. To keep the program secret and stop people from

asking too many questions about the number of test flights from a Vandenberg

Air Force Base it was initially called Discoverer, the cover story being that

the satellites were carrying small animals into orbit for research and then

being dropped back to earth to see how they were affected by the launch and

being in space but the only things we were really carrying were cameras. The

idea of taking pictures from space and then getting them back was one thing but

in the late 1950s just getting the newly developed Thor-Agena rocket safely

off the launch pad was another. It took 12 attempts before on August the 10th

1960 Discoverer 13 became the first man-made object to be safely recovered

from space nine days before the Soviets did the same with the Korabl Sputnik 2.

After the testing period which lasted up until Discoverer 39, the program's name

reverting back to Corona and it was classified as top secret and remained

that way until 1992. Unlike the satellites of today which stay in

orbit for years, the corona ones were only intended to be

there for maybe a few weeks most once the film have been exposed and returned

the rest of a satellite was no longer needed and they couldn't refill it so it

became the world's most expensive disposable camera system. Each corona

satellite used to panoramic cameras each with 610 millimeter focal length lenses

and they used 70 millimeter film that had a resolution of a 170

lines per millimeter, twice that of the best film used for world war ii

reconnaissance. Two cameras enabled stereographic imaging to be done

allowing the image technicians to better gauge the depth and size of objects seen

on the ground. Instead of taking just simple snapshots with the cameras

looking straight down from orbit, the lenses exposed the filmstrip as it moved

through a 70 degree arc. This moving lens was to avoid the movement blur caused by

the speed of a satellite and to get an almost continuous image strip of the

ground below making the maximum use of a film available. To stop the torque reaction

of the lens as it returned to the starting position from up setting the

satellites orientation, though lower heavier part of the lens on later models

continuously rotated to act as a counterbalance. The lenses themselves

were made from the finest materials and at a time were the most perfectly ground

lenses ever made. The satellites operated in a nearly polar orbit meaning they

traveled almost north to south where the orbit offset just enough so that it

would move a few degrees further around the globe with each orbit. In order to

accurately judge the size of objects a set of concrete calibration targets were

created on the ground around Casa Grande in Arizona that could be easily seen

from space. Each one was a shape of a maltese cross and about 18 meters in

diameter. 256 of them were placed exactly one mile apart or 1.65

kilometers in a 16 by 16 mile grid. Although they were abandoned in 1972 when the

program came to an end some 143 of them were still in position as of 2018. At the

beginning of the corona program the best resolution that could be seen was around

7 meters but with continual updates and improvements in both the film and the

cameras by the program's end it was down to one and a half meters. The amount of

film also increased as new thinner polyester based films were developed

that were also much more tolerant of a harsh conditions in space, something

which had plagued the earlier acetate films with breakages. By the end of the

program each satellite had two separate film buckets each containing up to

4900 metres of film allowing one to be dropped off whilst

the other was still in use. Once the film had been exposed and the mission

objectives had been covered it will be ejected from a satellite protected by a

detachable heat shield at around 60,000 feet a drogue parachute was deployed

before then the main chutes carried it down to around 15,000 feet here it will

be captured by planes trailing an airborne claw which when winched the

bucket onboard the plane. This method of airborne recovery became

so successful that it continued to be used on subsequent reconnaissance

systems well into the late 1980s and the Chinese were still using a similar

system for their spy satellites up until the 2000s. If a plane missed the film

bucket or for some reason it was off course and landed in the sea, it was

fitted with a salt plug which would dissolve after two days and sink the

bucket rather let it float around in the sea and possibly be captured by a foreign

power. But Corona was more than just a spy

satellite, it became a testbed for some of the key technologies that will be

used in programs like Gemini, Mercury and Apollo, from the re-entry of the Earth's

atmosphere at a specific point to splashdown and recovery from the sea at

a predefined area in the ocean. By 1972 Corona had done a 167

successful recoveries and photograph over 920 million square

kilometers of land. The photos the program took affected every major US

overseas military policy of a 1960s and beyond and stopped much of the

overreaction but had caused much of a mistrust between the U.S. and the

Soviets in the 1950s. Satellite reconnaissance became the cornerstone of

nuclear disarmament treaties for both sides with chopped-up bombers left in

the open for the other side to see from space. After it was Declassified in 1992

its archives revealed much more about the natural world and our ancient

history than had been seen from the air before and even now they are still used

to see the effect that we have had on the world over the decades since these

photos were taken. So what do you think of the early despising the sky and their

ingenious methods they used to get the images back to earth don't forget to

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