[Editor’s Note: this is the first of a two-part article.]

In 1995 the Central Intelligence Agency declassified the existence of the CORONA series of reconnaissance satellites, which had operated from 1960 until 1972. President Dwight D. Eisenhower, who had approved the satellite’s development in early 1958, was hailed by agency and military officials as a visionary who had approved a revolutionary intelligence collection system. But in 1960, after Gary Powers’ U-2 was shot down over the Soviet Union and high-resolution photography of Soviet targets ceased, Eisenhower approved a second reconnaissance satellite named GAMBIT that was equally revolutionary to the CORONA. GAMBIT produced very-high-resolution photographs of Soviet military installations until the last launch, in 1985. (Spy satellite names were almost always printed in all-caps in official documents.)

GAMBIT’s existence was supposed to be declassified in 1998. The bureaucratic paperwork was all signed and the last steps were being taken to release the information. However, something happened to prevent that. What is not exactly clear, although the Indian nuclear tests in May 1998, and evidence that the Indians may have deliberately hidden their actions from American reconnaissance, may have shifted the balance of the declassification argument in favor of those who opposed any discussion of American reconnaissance capabilities. In 2002, the US government released imagery taken by the first GAMBIT satellites, although it did not divulge any information about the spacecraft, refusing to even admit that the National Reconnaissance Office had launched them and in fact never even mentioning the name “GAMBIT.”

Eight years of a secretive Bush administration did not change the situation. However, now that a new President is about to take office, there is a possibility that secrecy rules may be loosened and the GAMBIT fully declassified. This was a Cold War system using technology that the National Reconnaissance Office officially declared obsolete over a decade ago. Hopefully, its contribution to American national security and international stability may now be told.

Despite the secrecy, significant details of GAMBIT’s history have already been revealed, both in documents and interviews conducted over the past several years. This two-part article is an abridged version of a series on American satellite reconnaissance that will probably appear in the British Interplanetary Society’s magazine Spaceflight later this year.

Secret satellite

The United States flew approximately two dozen U-2 aerial reconnaissance missions over the Soviet Union between 1956 and 1960 when Francis Gary Powers was knocked out of the air by an SA-2 missile. The U-2 produced beautiful photographs of its targets, regularly achieving ground resolution of two feet (0.6 meters) or better. But when it was no longer able to fly over “denied territory”, the American intelligence community needed a replacement. President Dwight D. Eisenhower approved one in August 1960. It was named GAMBIT.

Now that a new President is about to take office, there is a possibility that secrecy rules may be loosened and the GAMBIT fully declassified. Hopefully, its contribution to American national security and international stability may now be told.

When the new satellite project was first under discussion in the senior levels of the US government in early 1960, presidential science advisory George Kistiakowsky expressed his concern over the military’s ability to operate a covert program. The CIA had developed the highly successful U-2 spyplane and was then developing the CORONA reconnaissance satellite. But according to one source, the CIA “had no interest” in expanding its role to include developing this new reconnaissance system.

Air Force Under Secretary Joseph Charyk strongly argued that the new program should be developed by the Air Force. He stated that he could prove that the Air Force could develop a covert satellite. In the summer of 1960 Charyk and Colonel John L. Martin, Jr. invented a new security strategy called “Raincoat” that would be used to shield the covert development program. Raincoat worked by classifying all military space programs. The plan was that with everything classified, it would be harder for outsiders to detect the presence of a new reconnaissance satellite project.

According to one source, at first this project was known only as “Program I”. Sometime soon after the project gained formal approval, it was given the secret code-name designation GAMBIT. The origins of the name are still classified, but the satellite was a gamble, for it involved new and revolutionary technology. Perhaps equally risky, the White House gave management authority for the project to the Air Force, which by summer 1960 was under considerable criticism for its management of the Samos reconnaissance program.

In contrast to the publicity surrounding its counterpart, the Samos E-6 search satellite that was started at the same time, the covert effort to build GAMBIT did not leak to the press during the next several years. Dozens of people had sat in on a National Security Council meeting that gave a stamp of approval to the E-6. Probably no more than a handful of people were present when Eisenhower approved GAMBIT. The results were readily apparent on the pages of national magazines like Aviation Week—often referred to as “Aviation Leak,” where GAMBIT never appeared.

A new type of intelligence

When CORONA was started in early 1958 its purpose had been to develop the best reconnaissance camera in the shortest possible period of time. Initially CORONA was described as an “interim” system until something better came along. But its photographs could only show large objects such as buildings and airfields. GAMBIT’s resolution would be much higher and its purpose was “technical intelligence”, which meant the gathering of technical data about its targets. For instance, it was one thing to spot a missile site on the ground in the Soviet Union. However, if a satellite could provide a high-resolution photograph of an ICBM silo under construction it would be possible to measure the thickness of its concrete walls and determine how close an American nuclear warhead would have to strike to breach those walls.

The value of high-resolution reconnaissance photos was not simply the detail that they showed, but how they contributed to an overall understanding of what was happening on the ground. High-resolution photos enhanced the value of low-resolution photos. For instance, high-resolution U-2 photographs could be used to identify objects that were only blobs in CORONA photos. Similarly, after the United States flew low-level reconnaissance missions over missile sites in Cuba during the 1962 missile crisis, photo-interpreters were able to look at CORONA photographs of similar missile sites in the Soviet Union and identify blurry objects, which the aircraft photos revealed to be things like trucks, trailers, or tool sheds.

GAMBIT was intended to replace the U-2’s technical intelligence capabilities. Technical intelligence required high resolution. In order for GAMBIT to achieve it, the satellite had to carry a large camera that achieved its power both through brute force and ingenuity.

The U-2 spy plane. The KH-7 GAMBIT was intended to replace the U-2 in the dangerous job of producing high-resolution photographs of the Soviet Union. (credit: NASA)

A powerful telescope in orbit

GAMBIT was started after Eastman Kodak Company of Rochester, New York suggested adapting a high-power camera system that the company had apparently originally proposed for another purpose, probably an aerial reconnaissance camera for use in an RB-57 spyplane. Kodak’s design for the GAMBIT camera was bold, almost radical. The company’s engineers combined a reflecting telescope design and a film exposure technique known as a strip camera to achieve very high resolution.

Reflecting telescopes had been around for hundreds of years, particularly in ground-based astronomy. Extremely large and heavy mirrors had been used for decades. For instance, a 100-inch (254-centimeter) mirror telescope entered operation on top of Mount Wilson in 1917. The famed Palomar Telescope in California, built in 1948, had a mirror diameter of 200 inches (508 centimeters).

Kodak’s design for the GAMBIT camera was bold, almost radical. The company’s engineers combined a reflecting telescope design and a film exposure technique known as a strip camera to achieve very high resolution.

The design that Kodak proposed for GAMBIT in early 1960 was a compound mirror, meaning that more than one mirror was used to focus the image on the film. A large curved “primary” mirror with a hole in its center—like a donut—was located at the base of the telescope and a smaller “secondary” mirror was fitted in front of it. Light would enter the aperture, bounce off the primary mirror, which would focus it on the secondary mirror, which would then bounce it back through the hole in the primary mirror through a long thin exposure slit, where it would strike a platform at the camera’s focal point known as a platen. The platen held the film in place during exposure.

Because the light was folded inside the telescope, it could be shorter than a similarly powerful telescope using conventional lenses to focus the light down a long tube. It would be wider than such a telescope, but another advantage was that only a few mirrors were required and they could be made lighter than the many thick and heavy glass lenses used in a conventional telescope system.

Compound mirror designs were popular for ground-based telescopes but rare in most other applications. The military has used them for some purposes, such as weapons sighting systems and sniper rifles. They briefly became popular among photographers during the 1950s as lightweight telephoto lenses that did not extend far out in front of the camera and therefore made the cameras easier to carry and store.

But engineering is always about compromises, and there was an obstacle to applying this design to satellites that Kodak’s designers had to overcome. Because the mirror arrangement was large and relatively thick, they could not point it straight out of the side of the spacecraft. Normally a solution would be to point it straight out of the nose of the spacecraft and point that down toward the Earth; this was the approach used by the unsuccessful Samos E-1 and E-2 film-readout satellites. However, the new camera used conventional film that had to be returned to Earth in a reentry vehicle mounted on the nose of the spacecraft. So what the camera designers did was to mount a third mirror, known as the image-reflecting mirror, in front of the other mirrors. This image-reflecting mirror looked out through a camera port in the side of the spacecraft down at the Earth. It reflected the vertical light from the Earth horizontally and onto the primary mirror, the same way a submarine periscope reflects horizontal light down a vertical tube.

This image-reflecting mirror had to tilt forward and back. This enabled it to reflect images at different angles, probably a total of 30 degrees difference, providing a stereo capability that allowed the photographic analysts to measure the size of ground objects.

Even though reflecting telescopes had existed for decades, adapting them for spaceflight presented many challenges. The primary technical challenge facing the designers was making the mirrors relatively lightweight. Ground-based telescope mirrors were made of polished glass and weighed tons. In fact, they were deliberately heavy in order to counteract the gravity that distorted their shape and to reduce vibration. Mirrors for satellites had to be much lighter and made of special materials. The details of how Kodak’s engineers made the GAMBIT mirrors lightweight remain classified. One person who was involved with the GAMBIT program remembered that Kodak used quartz for its mirrors, which was not the lightest material then in development for satellite use. Beryllium was ideal, but it was hazardous to work with.

The primary mirror on the GAMBIT camera had a 44-inch (112-centimeter) diameter that filled up much of the 60-inch (152-centimeter) diameter of the payload cylinder that housed it. Overall, the camera had a 77-inch (196-centimeter) focal length, the distance from the point where light enters the camera—the surface of the primary mirror—to the point where it was focused, the film platen. As with all long focal length precision optics, temperature had to be precisely controlled. A small temperature increase would cause the camera materials to expand or contract, moving the mirrors out of focus. Camera designers for other cameras controlled temperature in a number of ways, including careful selection of materials with known temperature response, passive thermal control of the spacecraft environment through the use of shades and reflective paints, and the addition of small heaters at key parts of the camera.

The GAMBIT camera was the first time that a spacecraft employed a reflecting mirror telescope to focus the light, which was undoubtedly challenging. But the design was also revolutionary for another reason, the clever way that the camera actually exposed the film.

Elegance in motion

Powerful reconnaissance cameras have never really operated in the way that conventional commercial cameras do. A 35-millimeter single lens reflex (SLR) camera like those used by professional photographers works by opening a shutter to simultaneously expose the entire area of a rectangular piece of film. In contrast, many of the early reconnaissance satellite cameras developed by the United States did not expose a rectangular frame, but rather a long thin slit, taking advantage of the fact that the image at the center of a lens is sharper than the image near the edges, and covering much more territory.

Kodak’s design for the GAMBIT camera was bold, almost radical. The company’s engineers combined a reflecting telescope design and a film exposure technique known as a strip camera to achieve very high resolution.

In the case of the CORONA, the camera itself rotated, and the aperture, a narrow slit, was swept over a stationary piece of film, producing a long thin image during a period of several seconds. The CORONA camera design, first conceived in the mid-1950s, was advanced for its day, but also awkward. The tube, or “cell,” carrying the camera lenses had to be rotated. The lenses were heavy and rotating the cell produced vibrations. One Lockheed technician remembered that testing the CORONA camera system on the ground prior to flight produced a tremendous amount of noise, a clackety-clack sound that led them to force all people without the required security clearance to leave the building so they would not suspect what the payload was.

For GAMBIT, Eastman Kodak’s engineers proposed an entirely different way to expose the film known as the strip exposure technique. Strip cameras had first been invented in the 1930s by camera and reconnaissance designer George Goddard. Goddard was in many ways the father of American aerial reconnaissance and significantly advanced reconnaissance technology during World War II.

Goddard had the idea of pulling the film through the camera at the same speed that the camera was moving and exposing it along a thin vertical slit. The result was that the camera exposed a long strip of film. He initially used it to photograph racehorses at the finish line, where the racehorses appeared sharp and crisp.

Goddard realized that his strip camera could be valuable for aerial reconnaissance, where the platform was constantly moving. Normally the moving platform produces a slightly blurred image because the image moves inside the camera while the film is being exposed. But Goddard determined that if he could move the film at the same speed as the image moved inside the camera, the movements would cancel each other out and there would be no blurring. He employed this for reconnaissance planes during World War II, where the biggest problem was getting the pilots to fly an exact speed when they turned on their cameras.

Compared to an airplane, a satellite was an ideal platform, because the satellite would travel at a constant rate of speed in its orbit. The primary problem would be precisely determining that rate of speed. The designers would not know exactly what orbit the rocket would place the satellite in, but once it was safely in orbit they could track it from the ground and adjust the camera so that it pulled the film past the exposure slit at a precise rate of speed.

The result was a camera that had fewer moving parts and less vibration than the CORONA. Pulling film through a powerful camera was a much more elegant solution than rotating a heavy lens cell past a long strip of film.

The GAMBIT camera used nine-inch-wide (23-centimeter-wide) film, over three times the width of the 70-millimeter film employed in the CORONA camera. Nine-inch film was a typical size for large-format aerial reconnaissance cameras. The film did not have sprockets on its edge and was pulled through the camera by tension from the takeup wheel. The camera only exposed about 8.5 inches of the film width, leaving thin strips on either side for recording camera data, such as the reconnaissance mission number, the date and time, and the frame. This data was projected onto the film by small diodes mounted inside the camera.

There is a basic rule of optics that the more powerful the magnification, the smaller the field of view. This inevitable tradeoff also applies to reconnaissance satellites. GAMBIT had a powerful camera that could only focus upon a small bit of territory on the ground. From a normal orbit of 90 nautical miles (167 kilometers), the camera would see a strip approximately 12 nautical miles (22 kilometers) wide. However, the strip camera had one partial advantage, which was that it could expose new film as long as the shutter was open. So although the film imaged the ground 12 miles wide, there was virtually no limit to how long an image it could take. In practice, the KH-7 GAMBIT camera could take strips that were as short as 5 nautical miles and as long as 400 nautical miles (741 kilometers), although most strips were about twice as long as they were wide. The vast majority of ground targets could fit in such a strip.

There was one other limitation on how much the camera could photograph. Because the satellite used the same camera to take photos from different angles, if programmers wanted stereo photographs of a target they would have to turn on the camera, take a photo for a short strip, and then close the exposure slit, move the image reflecting mirror to its new position, and then open the slit again to expose a new piece of film. Other targets could be missed while the camera was doing all of this. In addition, starting and stopping the film meant that occasionally the image smeared a bit at the leading edge as the film accelerated from zero speed to the speed of the image through the camera. Operators could compensate for this by starting the camera before reaching the target, which wasted a small amount of film but ensured that the target would be sharp.

KH-7 reconnaissance satellite image. (courtesy J. Richelson)

Hawkeye’s spies in the sky

Eastman Kodak manufactured the GAMBIT camera at its secretive Hawkeye facility in Rochester, New York. Kodak manufactured and processed the high-quality film used in aerial and satellite reconnaissance cameras. The company also designed and built various reconnaissance cameras such as the Samos E-1, E-2, E-6, and GAMBIT. Kodak is not publicly known as a major defense contractor, and the company’s leadership prefers it that way. Even today Kodak’s former executives and employees remain tight-lipped about their role in developing some of the most powerful reconnaissance cameras ever built.

One young Air Force officer who traveled to view the GAMBIT camera manufacturing facility at the Hawkeye plant in the late 1960s remembered walking through a large cleanroom where dozens of women were assembling small commercial cameras. Because of the requirement for dust-free operations the women wore nothing under their white jumpsuits. The officer fondly remembered that the women occasionally flashed their bare chests at the Air Force visitors, which made the visit to cold Rochester worthwhile.

Hilliard Page, an executive at General Electric, the company responsible for the manufacture of the GAMBIT spacecraft and its reentry vehicle, remembered that dealing with the Kodak engineers was a lot different than dealing with the engineers at Itek, which manufactured the CORONA camera. Itek was a small, entrepreneurial firm that needed all the business it could get. Kodak was a massive, profitable corporation that did not really need the reconnaissance business. Its engineers were self-assured to the point of arrogance, and told Paige that everyone would do things their way or not do them at all.

Ellis Lapin, an engineer at The Aerospace Corporation who worked on GAMBIT from 1962 until 1966, remembered that his boss found Kodak difficult to deal with, but Lapin himself never experienced this. “In my own dealings with high level management and with the engineers at Kodak,” Lapin wrote, “I found the former deferential to a degree that surprised me and the latter cooperative and intent on doing a good job.”