After Gary Powers’s U-2 was downed on May 1, 1960, it became impossible for the United States to continue photographing the Soviet Union. But the need for Soviet intelligence didn’t change — it remained paramount to American national security to know what was happening beyond the Iron Curtain. Luckily for the United States, there was a new technology ready to take over the job of aerial reconnaissance within months of the Powers’ Incident: the Corona spy satellites.
This is part of my Cold War aerial espionage series. Part 1 about the U-2 plane’s genesis is here. Part 2 about the political challenge of deciding to fly it is here. Part 3 focussing on the Gary Powers Incident is here.
Eyes in the Sky
The Second World War saw rocketry mature as a technology, namely with the V-2 program in Germany. In the immediate post-war years, both the United States and the Soviet Union imported V-2 scientists to harness the new knowledge. The United States managed to import some of the German program’s foremost minds, including Wernher von Braun, who brought literal train cars full of V-2 parts and plans stateside with him. American engineers were thus able to rebuild the V-2 while learning about the technology, and in 1946, a team at the White Sands Proving Ground launched one carrying a camera. That V-2 captured the first image of the Earth from space. Photography from above the atmosphere was somewhat literally on the horizon. That same year, the RAND corporation undertook a feasibility study of orbiting satellites for data collection.
Rocketry became a primary technological focus in the United States in the late 40s and into the 1950s, and most of the funding came in developing this technology for national defence. The emphasis was on developing Intermediate-Range and Intercontinental ballistic missiles capable of carrying nuclear warheads to points around the globe, essentially building up an arsenal against potential aggression from the Soviet Union. This work led to three notable programs: the Redstone IRBM being developed by Wernher von Braun’s team now at the Army Ballistic Missile Agency, the US Air Force’s Atlas ICBM, and the Navy’s Vanguard sounding rocket.
While the military branches pursued various missile programs, RAND continued to study and develop the idea of reconnaissance satellites. In 1953, the program was transferred to the US Air Force’s Air Research and Development Command, bringing the idea firmly under the military umbrella. It was good timing. Almost coincident with the Air Force taking over the satellite program, the Air Force’s Scientific Advisory Board gave the Atlas missile a high priority status. The Atlas’ development had implications for satellites: if the missile could carry a warhead across the ocean, it would also be powerful enough to carry something smaller into orbit. In essence, the thrust to send a warhead across the Earth could be harnessed for an orbital trajectory with a less massive payload. The same could be said of the Redstone and Vanguard rockets, too — both could theoretically carry payloads into space.
The link between missiles and spaceflight found various outlets, but the one we’re interested in for this story comes in 1955 when General Operational Requirement №80 gave the objective of providing continuous surveillance of preselected areas of enemy territory. The idea of a satellite surveillance program fell under the Air Force’s Ballistic Missile Division.
Two years earlier in the fall of 1953, the CIA had begun pursuing a high-altitude reconnaissance plane. The Air Force officially taking on a satellite program now marked a shift in overhead reconnaissance in the United States.
The State of the Art
Traditional forms of espionage using human operatives became impossible after the Iron Curtain came down, shutting off communication with Eastern Europe. What WWII-era photography the Americans had was badly outdated. Better intelligence was necessary to manage the mounting Cold War, and the only way to look past the Iron Curtain was to go overtop of it. If a plane could fly high enough to avoid radar detection, which would also put it well out of range of intercepting missiles, it could fly into Soviet airspace to photograph missile and bomber sites without being seen.
That plane was the U-2. It was designed by Kelly Johnson and the Lockheed team to be invisible and invincible, but came with a time limit. Even before the plane started flying, CIA program managers knew it was only a matter of time before this cutting-edge technology became obsolete. Including Special Assistant for Planning and Coordination, Richard M. Bissell, the CIA’s leading advocate of technical over human intelligence gathering. He gave the U-2 two years of overflights before the Soviets would know enough about it to build defences against it.
The U-2 didn’t get two years of invisibility. It didn’t even get two flights. Hervey Stockman left the base in Wiesbaden on July 4, 1956, and flew over Poznan, Poland, Belorussia, then headed north towards Leningrad before flying over the Soviet Baltic states. Carmine Vito followed a similar path the next day but flew further east, going more than 200 km past Moscow. Soviet radar picked up both flights almost immediately, and though it seemed the Soviet fighters couldn’t track the U-2s well enough to intercept them, the plane was no longer a secret.
That same month — July 1956 — the Air Force approved a satellite development program called Weapons System (WS) 117L. Four months later, the prime contract was awarded to the Lockheed Missile and Space Company.
WS-117L to Corona
WS-117L was originally conceived as a program to explore and implement reconnaissance satellites for national security. The idea was to house various electronic intelligence (ELINT) and imagery intelligence (IMINT) setups within a single system housed in the Lockheed upper stage that eventually became known as the Agena. And unlike the U-2 program that returned film to be developed then analyzed, WS-117L aimed for near-realtime data with the E-1 and E-2 systems. The best available technology at the time was television cameras, but they were too slow to image anything from orbit properly. To bypass the lag of TV cameras, the E-1 and E-2 systems used a regular film camera to photograph sites of interest from orbit. That film would be stored and developed on board the Agena, and once processed, scanning cameras would image the film and relay the images back to Earth.
Like the U-2 program, WS-117L gave Eisenhower pause. Though he was keen on a technology that would return intelligence without violating Soviet airspace, he was also keen to keep the military out of space.
Eisenhower’s resolve on this point was strengthened after the Soviets launched Sputnik on October 4, 1957. The small satellite beeped from orbit, but it raised fears among the American people that the Soviets were spying from space. Experts knew the satellite itself was harmless and that the real worry was the R-7 launch vehicle’s power. The R-7 that launched 184 pounds into orbit could launch something heavier across the Earth, like a nuclear warhead from Russian to the United States. Sputnik pushed America’s nascent space efforts forward and also bred fears over the Soviet’s missile powers. The question had been over the bomber gap when the U-2 started flying. Now it was over the missile gap.
U-2 overflights were ongoing when the President’s Board of Consultants on Foreign Intelligence Activities sent its semiannual report on October 24, 1957. It listed two technologies then under development to gather data on Soviet technologies: a new manned high-altitude plane with a smaller radar cross-section than the U-2 and an unmanned reconnaissance satellite system.
Eisenhower gravitated to satellites over continued overflights. On October 28, he asked Secretary of defence Charles Wilson and Director of Central Intelligence Allen Dulles for a status report on this nascent technology. The report ended up being a verbal one to avoid any written records falling into the wrong hands, and in the months that followed, more in-person meetings shaped the program. Major players agreed that the WS-117L photographic subsystem represented the best chance of success and should thus be separated into a standalone program called Corona. While early talks were still underway, a new agency joined the discussion. The Advanced Research Projects Agency or ARPA — which is the precursor to modern-day DARPA — was established on February 7, 1958, and was immediately granted authority over military space projects.
An ARPA directive on February 28 and the CIA’s assuming responsibility for security arrangements around WS-117L in March finalized Corona’s separation. It was now a program to develop a mid-sized satellite that would launch on a Thor-Agena stack; Thor would be first stage and Agena the second stage that would also house the imaging system. Like the U-2, it was officially a joint CIA/ARPA/Air Force program, though it developed into more of an ARPA/CIA program with Air Force support. Special Assistant to DCI Allen Dulles for planning and development, Richard Bissell, and Brigadier General Osmond Ritland were the prominent management voices representing the CIA and US Air Force respectively. From the start, the program was marked by civility. None of the organizations involved wanted credit; they all just wanted to get the job done. WS-117L, meanwhile, lived on under the Air Force umbrella.
Corona took shape as it developed into a dedicated, standalone program. One of the first things to go was the goal of near-realtime imaging. While scanning the photographs was viable, relaying them to Earth was not. The bandwidth for this transfer was beyond the limits of technology at the time. So planners started considering an alternate method. The near-realtime goal became a separate project called SAMOS. Corona took shape as a stop-gap while technology caught up, and the interim solution was physical film recovery.
With this decision made, planners focussed on the actual spacecraft. In March of 1958, Lockheed presented a spin-stabilized football-shaped payload design to its counterparts — the CIA, the Air Force, the Ballistic Missile Division, General Electric, and Fairchild, the company building the camera. But the arrangement soon changed. The Itek company was building a new camera that Bissell was more excited about than the Fairchild design, even though it eschewed the spin-stabilization system for a 3-axis stabilization system. Bissell eventually changed Corona’s camera system, abandoning Fairchild as a contractor. To lessen the financial blow, Fairchild was brought on as the subcontractor to Itek.
The camera hardware was designed to be part of the Agena, meaning the stage had to alter its attitude to point the camera at its target. As the film was exposed, it would spool into an onboard bucket, properly called the reentry vehicle. Once the full load of film was exposed and spooled, it was time for reentry. The Agena would pitch down through 60 degrees to put the satellite in retrofire orientation. The retrorockets would fire, then the satellite recovery vehicle would separate from the Agena. Spin-stabilization rockets would maintain the recovery vehicle’s attitude as it fell through the atmosphere, through the retro-rocket thrust cone separation and heat shield and parachute cover deployment.
Once the recovery vehicle reached thick enough atmosphere, the drogue parachute would deploy, followed by the main chute that would slow its fall in a designated recovery area over the Pacific Ocean near Hawaii. And here’s where the decision to recover the film gets really tricky. To avoid the film falling into the wrong hands, the primary recovery method called for a pilot to fly a C-119 or a C-130 aircraft over the top to descending capsule and snag the parachute or its shrouds with a trapeze-like hook suspended below the fuselage. If the pilot missed, the recovery vehicle was designed to float long enough for backup crews to fish it out of the water, but not so long that a foreign ship could find it. The capsules would eventually sink, burying the intelligence with them.
In theory, this recovery method was simple, but it proved difficult in practice. When the 6593rd Test squadron practiced catching descending payloads mid-air, pilots only recovered 49 of the first 74 drops. A different type of parachute saw four out of 15 drops recovered. Eleven drops with yet another kind of chute saw only five recoveries. Regardless of the parachute type, the recovery rate was low, but that wasn’t all. On average, it took one-and-a-half passes to snag the chute, which meant even the successful recoveries weren’t smooth. Issues were chalked up to crew inexperience, but the canisters’ fast fall rate made it a hard method to learn. Still another kind of chute was eventually developed with a slow enough sink rate for a reasonable chance of air recovery, bringing some reliability to the method.
The in-flight and recovery sorted, the final program consideration was getting Corona into orbit. For the Corona satellites to cover Soviet territory, they needed to launch into a near-polar orbit, which meant the missions couldn’t start at the Air Force’s Cape Canaveral launch site that was perfect for equatorial launches. The best launch location for Corona turned out to be near Arguelo, California, a site that not only facilitated polar launches, rockets launching southward went safely over the Pacific Ocean. It was great for range safety. The location was perfect, but the site didn’t exist. A new facility would have to be built at Cooke Air Force Base, which was renamed Vandenberg AFB in October of 1958. There was only one lingering challenge with the launch location: the Southern Pacific railroad passed close to the base. The workaround was setting launch windows around the train schedule, even if it meant a break in rail traffic was just a few minutes.
These major decisions made, Corona’s final configuration was sent to White House Chief of Staff Andrew Goodpaster on April 16, 1958. He passed it to Eisenhower, who approved the program; the official record was a handwritten note on the back of an envelope taken by General Charles Pearre Cabell, the Deputy Director of Central Intelligence.
Hiding in Plain Sight
The last challenge was figuring out the cover story for Corona since there was no way people wouldn’t notice rockets flying over the California coast.
The WS-117L program wasn’t a public secret; it wasn’t openly talked about, but it wasn’t highly classified, either. Managers knew linking Corona to WS-117L at all would both draw unwanted attention to the government reconnaissance programs and reveal the satellite’s true nature. The solution lay in the nation’s very public space program. On December 3, 1958, a press release announced the Discoverer and Sentry programs, which were Corona and SAMOS, respectively. The public was told that both programs would be exploring space, environmental conditions, and launching biomedical specimens, and that ARPA would participate by developing radiometric payloads. Corona was thus disassociated from Sentry/Samos and protected by Discoverer.
With all the pieces falling into place, the first Corona design review came on May 14, 1958, and the design was frozen on July 26. Already the first launch tentatively on the books for mid-1959. As part of the lead-up, the Vandenberg launch site was finished. This Air Force operational missile training site became home to the 672nd strategic missile squadron working specifically with the Thor missiles. Manufacturing and other program personnel were all moved to the area as they prepared to launch from California and recover the film near Hawaii.
Getting off the Ground
The Thor-Agena program supporting Corona got off to a rocky start, which was par for the course for rocketry in the late 1950s. But even for the 1950s, Corona had a lot of growing pains.
On January 21, 1959, the first Thor-Agena mission, and the first launch from Vandenberg, was aborted t-minus 60 minutes. Power was applied to test the Agena’s hydraulic system, triggering the explosive bolts connecting it to Thor boosted. The ullage motors fired, and the Agena settled into its fairing, sustaining significant damage. This failure was never given a formal designation — much like how the Soviets hid their launch failures with non-consecutive mission designations.
That was the first of many problematic attempted launches. By the end of 1959, the program had experienced one misfire, three orbit insertion failures, two high eccentric orbit, one premature ejection, three partial or complete camera failures, one retrorocket malfunction, one temperature failure in the payload bay, and failures of both the camera and the capsule return method. These specific failures were all symptomatic of larger, more serious issues that would continue to affect the program if left unaddressed. A Corona panel finally met to discuss the extensive list.
The launch profile explained the orbit insertions problems. The Thor-Agena stack demanded the Thor burn all its fuel rather than having the engine cut off at a predetermined pointed velocity. This inaccurate profile introduced the potential for trajectory variations that could compound when the Agena fired. A more powerful Agena with lighter instruments would help remedy the problem, but in the meantime, engineers had to literally shave off weight with a file and tin snippers to keep the stack’s mass low enough for the correct launch profile meant.
One issue behind the camera failures was the film. It was designed to operate in an unpressurized cabin, a decision made to save weight, but the vacuum caused the acetate base film to tear, which in turn caused the camera to jam. A new, more durable polyester film solved that problem. Cabin temperature was another cause of camera failure. Again to keep mass down, the camera’s cabin was heated purely through passive thermal control — the Sun provided natural heating. But it wasn’t stable; early missions saw a huge variety of inboard temperatures. An interim solution with a minimal weight penalty was adding thermal paint.
The spin stabilization rockets explained problems with the capsule’s return: they tended to explode rather than fire. Changing to a cold gas system promised to solve the problem. A more challenging problem to solve with recovery was getting the recovery vehicle to come down in the recovery zone. A one-second delay in firing the retrorockets translated to a five-mile difference in landing site, and that was a huge error when a pilot had to snag the falling payload’s parachute.
Adding to the Corona team’s mounting stresses in solving these issues was the Navy’s success with its own satellite program. On June 22, 1960, the Navy launched a successful Galactic Radiation Background Experiment — GRAB — satellite that carried an electronic intelligence or ELINT system that gathered information on Soviet air defence radars. Corona, meanwhile, needed “qualification, requalification, and multiple testing of component parts” before more missions could resume, but there was no question of cancelling the program. Problems aside, the satellites were getting into orbit, and while GRAB could detect radar, it couldn’t photograph airfields or missile locations.
To give the Corona research and development team time to solve the bevy of issues, a stand-down was in effect from November 20, 1959, to February 4, 1960 when the ninth Discoverer mission launched. This one also failed to achieve orbit.
Discoverer 10 launched on February 19, 1960, and though it was the first time film was recovered from a mission, it was in a way that made no one happy. The Thor booster fishtailed and was destroyed by range safety after 52 seconds. The payload was picked up nearby by a crew in a jeep. By April 1960, there had been eleven launches in and not a single success, forcing another stand down to make time for more troubleshooting. The next mission, a diagnostic flight for Discoverer 12, saw the Agena fail to reach orbit.
The need for viable intelligence increased as the failures piled up. As the Soviets launched increasingly sophisticated and heavy payloads, fear over the nation’s missile arsenal increased. The perceived missile gap took centre stage in 1960, becoming one of the key points in the Presidential race between John Kennedy and Richard Nixon. Meanwhile, President Eisenhower decided to take a decisive step and authorized an audacious and extremely risky U-2 Soviet overflight.
That flight took off early in the morning on May 1 ended with Gary Powers’s U-2 being downed deep over the Soviet Union. Soviet overflights were officially finished, and there was still no information about the nation’s true military capability. GRAB satellites couldn’t image missile installations. The Sentry system was still under development but far in the future. Corona had to work.
Discoverer 13 launched on August 10, 1960, a repeat of the diagnostic flight, and it all finally worked. Almost. The capsule came down outside the primary recovery area and was out of the ocean, but it was nevertheless a tremendous win for the program. The mission was widely celebrated under the Discoverer cover story. News photos showed the Ocean recovery, and Eisenhower displayed the capsule and flag it had carried to the press. Finally, Discoverer 13 was definitive proof that the Corona system worked. Even though this mission had no film on board, it proved orbital espionage was a viable option. The New York Times also saw that potential writing in the August 12 issue that flight’s technological advances could surely be used for spying from space.
Coming to Fruition
On August 17, the show trial over Gary Powers’ flight ended. He was found guilty of espionage, and his sentence was ten years deprivation of liberty. On August 18, Discoverer 14 launched on the first complete Corona mission.
The mission wasn’t without its problems. The Agena had to use a lot of fuel to correct its orientation once in orbit. But once this was done, the full 18 feet of film was exposed. The bucket was ejected, and Captain Harold E. Mitchell piloting a C-119 snagged it on his third pass over the falling payload.
The film was delivered to Photographic Interpretation Centre for development and analysis. The resolution was much lower than photographs returned from U-2 flights, and some images had strange artifacts like plus/minus density bars related to onboard fluid leaks and some marks caused by the actual Corona electrostatic discharge from the Sun. But issues aside, the intelligence was outstanding. This one mission had covered more territory than all the U-2 missions combined, some 1.5 million square miles of Soviet land, airfields and 26 new Surface-to-Air missile sites. It even covered areas unreachable by the U-2 with its 24-inch focal length camera that resolved objects as small as 40 feet across, allowing analysts to count individual bombers at airfields. It also photographed missile locations. In one mission, Corona had disproved the existence of a missile gap.
And this was just the beginning.
The Discoverer 14 camera was retroactively given the security designation of Keyhole 1 or KH-1, and there were other, more sophisticated cameras were coming out of the WS-117L program for later missions. This raised the issue of managing all the incoming intelligence not just from Corona but the other programs as well — GRAB and SAMOS. To pull together the growing amount of data, the CIA and Department of Defense jointly established the National Reconnaissance Program on September 6, 1961, as the umbrella organization to manage all military and government espionage programs, which also included the still-nascent A-12/Oxcart/SR-71 spy plane. The office was co-directed by Undersecretary of the Air Force Dr. Joseph Charyk and Richard Bissell working out of the Pentagon.
The next missions in the Corona series were a mix of partial successes and failures but saw one major step forward with Discoverer 18. Launched on December 10, 1960, this mission debuted the larger Agena B stage that was able to support longer missions with more film, in this case, 39 pounds feeding into the updated KH-2 camera. The images from this flight resolved objects as small as 35 feet across, confirming results of earlier missions.
Updating the State of the Art
As the program continued, the camera technology went through upgrades that meant later missions yielded better results.
On the heels of the KH-2 camera was the KH-3, a new model with minor enhancements. This version debuted on August 30, 1961, as the payload of Discoverer 29. But analysts needed better imagery, and stereoscopic imagery to really understand the Soviet missile sites they were photographing. Using the available technology, engineers achieved this goal by combining two KH-3 cameras into a single Agena payload: one pointing forward and the other aft, photographing a swath 15 degrees from vertical in both directions. The resulting images aligned created a stereo look at that swath of ground. This became the MURAL variant and the camera system known as KH-4. This system added a new index camera to take small scale photographs to simplify terrain identification.
But before KH-4 could launch, its numeric successor, KH-5, flew; it flew even before KH-3. KH-5 was called ARGON. Its first launch on February 17, 1961, was the first of several failures. There were twelve ARGON missions, only five of which worked.
MURAL ultimately became Corona’s workhorse, with later iterations increasing its yield. The KH-4a and KH-4b variants doubled the film supply to 160 pounds with a maximum resolution of objects five to six feet across. The uprated KH-4 system also used two buckets, which meant one film reel could be jettisoned and returned while the other remained in orbit working. Doubling the return from one flight was a serious boon to the program. Fifty-two KH-4a systems launched, returning 94 buckets between 1963–1969. The KH-4b system returned 32 buckets over 17 launches between 1967–1972.
Even as these better cameras found success, analysts wanted more resolution. In June of 1963, a new system called LANYARD launched, also known as KH-6, a camera system designed to resolve objects just one foot across. KH-6 was a version of the SAMOS system, one of the original designs under the WS-117L research program. KH-6 attempted to aim its optics independently rather than maneuvering the whole spacecraft with a dedicated roll joint covering 192 nautical miles across the length of the spacecraft’s flight path. But the cameras could only adjust 200 times per mission, and it was slow; it took three seconds to move each 15-degree increment and 30 seconds to move from one extreme to the other. LANYARD only launched three times and never yielded the results engineers and analysts had hoped to see.
While ARGON, Lanyard, and MURAL were under development, so was a proper successor to Corona. But CIA experts ultimately decided it would be cheaper and more efficient to continue developing Corona’s capabilities than undertaking an entirely new program.
Corona After Discoverer
The Agena upper stage failed on the Discoverer 37 mission in January of 1962, marking an unceremonious end of the Discoverer program; the cover story had simply run out. The next Corona mission launched on April 18, 1962, and was openly part of a secret CIA program. Other versions continued flying, too, including MURAL, which saw twenty-six missions before its final flight on December 21, 1963; twenty of them were recovered, all but one by air snatch. Of the six that failed, two were launch failures, one didn’t reenter correctly, and three sank.
The later iterations kept launching with various improvements. In 1963, a cluster of smaller rockets was strapped to the Thor booster, increasing its power at launch. The SAMOS system with a longer focal length made for better pics. Some missions flew low over target areas for the sake of resolving details, necessitating new orbital adjustment systems to compensate for the rapid decay that came with these lower orbits.
There were also some new elements to the continued reconnaissance missions. Infrared film limited dependence on daylight, but there remained no way to get around cloud cover. The CIA and Air Force needed better ability to track clouds. On June 21, 1961, the Office of the Secretary of the Air Force initiated a Defense Meteorological Satellites Program to support Corona with better weather data. By October 1962, meteorological satellites had paid immense dividends to the program.
As the 1960s drew to a close, there was again talk of a new system to replace Corona entirely, KH-9. KH-9, sometimes referred to as Big Bird, was an updated system that also came out of WS-117L, marrying a mapping camera with high-resolution cameras. Between 1971 and 1986, nineteen HEXAGON missions covered 877 million square miles of land still using the Corona-style film return system. They arguably gathered the best-ever images of the Earth from space.
The year after KH-9 first launched, the Corona program was officially cancelled; it came to an end in 1972. In its 12 years, the program had a pretty astounding life. What was meant to be a short interim program lasted far longer than anyone had planned, gathering crucial Cold War intelligence that helped multiple Presidents shape international politics while navigating the Cold War. In total, the Corona family of satellites returned more than 100,000 images and 2.1 million feet of film over 39,000 separate reels. This system that some have called an “assemblage of objects designed to replace the U-2” made immeasurable contributions to US reconnaissance.
The only thing Corona couldn’t do was realize the dream of near-real-time satellite imaging. This was finally achieved in the late 1970s with electronic film-optical readout technology developed under the NRO’s Project B Office. It used a charge-coupled device that modern digital cameras use.
Of course, satellite imagery from space didn’t stop with KH-9. Satellites photographing the Earth have become exceptionally commonplace.
Sources, in addition to those linked in the text: Declassified WS-117L Records from NRO; Index, Declassified WS117L, SAMOS, and SENTRY Records via NRO; Corona Fact Sheet NRO; “Corona Comes in From the Cold” by Theresa Foley, Air Force Magazine 1995; Corona Reconnaissance Satellite via DARPA; USGS Declassified Satellite Data; Corona Pioneers via NRO; “Corona: America’s First Satellites Program” Kevin C. Ruffner ed. CIA History Staff; “What We Officially Know: Fifteen Years of Satellite Declassification” by Jeffrey A. Charlston in Quest v.17 n.3 2010.