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An illustration of satellites flying over Earth.

Cold War watchmen

By Virginia Grant |July 13, 2020

In the 1960s, Los Alamos scientists changed the landscape of national security with Project Vela—satellite instruments that could detect nuclear explosions in space.

In December 1961, physicist Ian Strong moved to New Mexico to work at Los Alamos Scientific Laboratory (LASL). To work on what project? He had no idea. “I didn’t know what I was going to be working on when I came here,” he says. “They didn’t tell people what they would be doing when they got hired.” Upon arrival in Los Alamos, he had to wait for his security clearance so he could go into a secure area. There he was told he was being added to a team of scientists already at work on Project Vela, a program to develop satellite instruments that could detect nuclear detonations in the upper atmosphere and outer space.

The eye in the sky

On October 4, 1957, the Soviet Union launched the first satellite into outer space. For many Americans, Sputnik, whose name translates to “fellow traveler [with the earth],” was simultaneously a source of awe and fear, excitement and anxiety. Although the idea of a human-made creation circling Earth was thrilling, Sputnik was also a frightening reminder that the U.S.S.R. had achieved something the United States had not. Even more troubling was the fact that the Soviets could use the same technology that shot Sputnik into space to launch an intercontinental ballistic missile that could carry a nuclear weapon to American soil. Sputnik therefore played a major role in America’s decision to advance in the space race and to maintain superiority in weapons development.

A time-lapse shows x-rays in outer space, as recorded by Vela satellites.

As technology continued to advance during the Cold War, the United States also began to launch satellites, and America and the U.S.S.R. continued their weapons-development programs. Both countries tested nuclear weapons throughout most of the 1950s and early 1960s by way of underground, surface, and atmospheric tests (including some that were high-altitude), though each nation would at times announce periodic halts in testing. But when one country began testing again, the other would also resume. (This period included the American Argus tests, the first nuclear tests in outer space.) Each country felt compelled to answer the other’s tests, and each round of tests pushed the technology further, forcing the countries to keep up with each other. Although a treaty would have relieved some of this tension, this was the Cold War, and the United States could not take the risk that the Soviets would continue testing even after a treaty was signed.

A graph comparing the mushroom cloud heights of Little Boy, Fat Man, Castle Bravo, and Tsar Bomba, with the shortest cloud being from Little Boy and the tallest being from Tsar Bomba.

In early 1959, during a period when neither the Americans nor the Soviets were testing, a group called the Buzzer Committee was formed by LASL and Sandia National Laboratories to determine whether satellites might be used to detect nuclear explosions at high altitude or in outer space. Also interested in test-monitoring technology, the Department of Defense funded the Advanced Research Projects Agency (ARPA) to back detection research; ARPA funds set Los Alamos physicists in the P-4 group to work creating instruments that would change the battleground of the Cold War. This was the beginning of Project Vela.

The P-4 physicists designed sensors that would detect the radiation produced by a nuclear blast: x-rays, gamma rays, and neutrons. P-4 then flew prototypes aboard Sandia-built Deacon-Arrow rockets in 1959, and in 1960, the Air Force started allowing LASL to test detection instruments on Air Force Atlas missiles. Sandia was responsible for developing the systems for recording and transmitting information.

A nuclear test in space or in the upper atmosphere can be difficult to detect. The blast creates such a high temperature that the energy is emitted almost entirely in the form of x-rays, which are invisible to the human eye.The emitted x-rays, gamma rays, and neutrons quickly disperse, so distant blasts can be dim. Furthermore, these emissions can’t penetrate Earth’s atmosphere—ruling out ground-based detection. Conducting a test behind the moon is another way to conceal an explosion.

As the LASL News explained in 1963, “LASL, knowing more about nuclear weapons than any other laboratory, was the logical research center to set the pace” for the development of sensors. With a history of diagnostic equipment dating all the way back to the Trinity test, Los Alamos was prepared to take on this next important role for national security.

Tensions build before satellite launch

As Los Alamos physicists worked at a breakneck pace to develop instruments that would safeguard a test ban treaty, the Cold War intensified. On May 1, 1960, CIA U-2 pilot Francis Gary Powers was shot down by a Soviet surface-to-air missile near the city of Sverdlovsk Oblast in the U.S.S.R. Powers was able to safely parachute from the plane, but he was captured by the KGB. As events unfolded, the United States was unable to provide a feasible alternative to the truth—that Powers was flying a spy plane. This resulted in heightened tensions between Soviet Premier Nikita Khrushchev and President Dwight Eisenhower. (Powers returned home after being traded for a Soviet spy in 1962.)

A timeline of Cold War events.
Cold War events intensify, leading to the need to detect nuclear explosions in space and the Limited Test Ban Treaty. Los Alamos National Laboratory

On April 12, 1961, the Soviets pulled into the lead in the space race when Yuri Gagarin became the first human to travel into space. Just two months later, ARPA approved funding for five Vela launches (in the end, there were six). That same year, the Soviets began a series of huge atmospheric nuclear tests, including the October 30 test of Tsar Bomba, the most powerful nuclear weapon ever detonated, with a yield of 50 megatons—the equivalent of about 2,380 Fat Mans or more than 3,300 Little Boys. At the time, the United States was conducting underground nuclear tests, but in 1962, America resumed atmospheric nuclear testing with Operation Dominic. This included Project Fishbowl, a series of space tests meant to apply more scientific rigor than the Argus tests. The biggest test of the series, Starfish Prime, yielded 1.4 megatons and an electromagnetic pulse (EMP) so intense that it knocked out streetlights and telephones in Hawaii, about 900 miles from the site of the launch. It is also estimated that at least six satellites were damaged in that blast (one of which was worked on by Ian Strong before he joined P-4).

Then, in October 1962, the Cuban Missile Crisis brought the two superpowers as close as they ever came to nuclear war.

This series of escalating Cold War events further emphasized the tenuous nature of a signature-only test ban treaty, but it also stressed the need for one. If the United States could verify a treaty, it could enhance global security and help prevent nuclear war.

Although the United States didn’t know it at the time, its last atmospheric test was Clean Slate III, a safety test conducted jointly with the United Kingdom in Nevada on June 9, 1963. The Soviets’ last atmospheric test took place a few months earlier, in December of 1962, the same month that John Kennedy became the first president to visit Los Alamos. He also went to Sandia, where he viewed a skeletal mockup of a Vela satellite. (Sandia and Los Alamos partnered on the detection sensors and electronics, while the satellites were developed and produced by TRW Inc. for the U.S. Air Force.) “Kennedy wanted a test ban treaty,” says Doyle Evans, a retired Los Alamos physicist who worked the entire span of the Vela project. “And he had a lot of trouble getting agreement on that until he had assurances that it could be monitored. So it was very important to get the Vela satellites in place and operating.”

President Kennedy, surrounded by several men, looks at a mockup of a Vela satellite.
President John Kennedy views a skeletal mockup of a Vela satellite during a 1962 visit to Sandia National Laboratories. Kennedy visited both Sandia and Los Alamos before the first Project Vela launch. Los Alamos National Laboratory

Assurances in place, the Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space, and Under Water—more commonly called the Limited Test Ban Treaty (LTBT)—was signed in Moscow on August 5, 1963, by U.S. Secretary of State Dean Rusk, Soviet foreign minister Andrei Gromyko, and British Foreign Secretary Alec Douglas-Home. The LTBT banned the testing of nuclear weapons anywhere except underground. It was a watershed treaty that changed the course of nuclear testing, but it wouldn’t have happened without Project Vela. After the Senate was convinced not only of the merit of the treaty but also of the scientific ability to enforce it, the treaty was approved, and it was signed by President Kennedy on October 7, 1963. It went into effect three days later, and one week after that, the first pair of Vela satellites was launched.

First watch

On the morning of October 17, 1963, an Atlas-Agena-D rocket was launched from Cape Canaveral Air Force Station in Florida carrying the twin satellites Vela 1A and Vela 1B.

“We knocked ourselves out there for a while getting ready and getting our instruments constructed,” remembers Jerry Conner, a retired Los Alamos physicist who worked on Project Vela from the beginning. “We spent a few days in Florida, running checkouts of the instruments mounted on the satellites, which were on the rocket in the big NASA assembly building.”

Doyle Evans remembers being nervous. “We knew the instruments had to be working perfectly when they left the ground,” he says, “and hopefully they would still be working when they got into orbit.”

“The biggest thrill,” Evans says, “was to go up on the tower where the rocket was sitting and do the last-minute adjustments to the satellites.”

Ray Klebasadel, another member of P-4 from the beginning of the project, also remembers the last-minute preparations. “Although I wasn’t directly involved, I recall that during one prelaunch preparation, part of the logic system was dissembled to correct a problem just before the satellite was mounted on the rocket. So the team had electronic boxes and modules scattered on the workbench, working on them actively, when we were in final testing. That was a stressful situation, but it all worked well.”

After the launch, the scientists climbed into an Air Force plane and flew straight to an Air Force data processing center in Sunnyvale, California. Once there, in a windowless building called the Blue Cube, they studied large reels of Vela data on magnetic tape. Initially, they made sure everything was operating correctly and determined whether the project would yield a workable series of detection systems. The first Velas were not intended to function as detection satellites, but rather to establish if such a system was feasible. Velas 1A and 1B were such a success, in fact, that for years after, scientists studied those initial tapes looking for evidence of nuclear detonation. “The launch was very successful,” Conner remembers. “The instruments worked correctly. There was a lot of excitement in seeing the instruments we made functioning up in space, doing their jobs.”

A news release from LASL lauded this monumental contribution to national, and global, security. “The unblinking eye in the nuclear blast detection satellites now in orbit some 60,000 miles in space are products of the Los Alamos Scientific Laboratory, where the nuclear weapons age was born during World War II.”

Part of what made Project Vela so remarkable was the speed at which Los Alamos scientists were able to figure out how to make such important instruments work in outer space. “The Vela satellite program was revolutionary at the time,” says Marc Kippen, Nuclear Detonation and Test Detection program manager. “In retrospect, it continues to be astonishing how much was accomplished in such a short time with extremely limited prior knowledge of the space environment.”

Dave Smith, a project leader in the Intelligence and Space Research (ISR) Division, agrees. “Today we still find it very challenging to build high-performance sensors that can survive a rocket launch and then withstand the space environment for a long-duration, on-orbit mission,” he says. “That our predecessors were able to do the same thing in the 1960s without modern-day tools and without our current understanding of the space environment is impressive.”

Two men look at a photo of the interior of a Vela satellite.
Los Alamos physicists Richard Taschek (left) and Jerry Conner look at a photo of a first-generation Vela satellite’s interior instruments. Los Alamos National Laboratory

How to spot a space bomb

From Spanish, “vela” loosely translates to “watchman.” Referred to in the press as “sentries,” the Vela satellites were launched in pairs so they could view the whole Earth at once—one satellite per half the globe. The Vela satellites orbited about 60,000 miles from Earth, each with a sensing range of 200 million miles. Each satellite had 20 sides (an icosahedron), with x-ray detectors mounted on each of its 12 points. More instruments were stowed inside the satellite for detecting x-rays, gamma rays, and neutrons.

“If there was a bomb,” Strong explains, “then they could see that the radioactive products that came out of the bomb decayed in a specific way.” Some of the instruments were developed specifically to recognize detonation emissions, but some were developed to gather information about the background of outer space so nuclear detonations would stand out.

The satellites were capable of real-time data transmission, and they could transmit their collected data when signaled to do so by radio transmission from Earth. The data was collected at an Air Force processing center in Sunnyvale. There, LASL scientists studied the data on giant printouts, looking for information about what was happening thousands of miles above Earth.

At the time, so little was known about the space environment that preparing the Vela instruments was in many ways a series of trial-and-error experiments, and LASL scientists made some of the instruments adjustable from Earth after the satellites were in orbit. The technology used on the Vela satellites wasn’t new, but getting this technology to work in space was, and many factors required experimentation and creativity.

“Scientific principles involved in the instruments were old in terms of radiation measuring,” a 1963 LASL press release explained, “but the degree of sensitivity desired and the durability required to withstand launch acceleration and continual operation in orbit were problems for which there was no experience to draw upon.” The innovation of these instruments continued throughout the project, and nuclear detection technology used today is built on these designs. The Vela instruments, Strong says, “improved each time, right through the end.”

An artistic rendition of a Vela satellite orbiting the earth.
A Vela satellite in orbit, as depicted by an artist. Los Alamos National Laboratory

Academic cold warfare

The instruments built for Project Vela had significant impact not only on national security but also on scientific discovery. “Vela was the prototypical project that made Los Alamos the premier scientific national security laboratory in the world,” says Ed Fenimore, an Emeritus Fellow at Los Alamos, who has used Vela data in a great deal of his work. Los Alamos’ scientific prowess is a major reason the LTBT was so successful. In the mid-century Cold War, displays of military and technological superiority were often demonstrated through nuclear weapons testing. But in 1965, the scientists working on Project Vela exhibited the United States’ scientific superiority without firing a single detonator. By publishing the details of what the Vela satellites were detecting at every moment and how they were accomplishing it, they proved that we had the technology to detect nuclear explosions at high altitude or in space.

The publication was a special “Nuclear Test Detection Issue” of Proceedings of the IEEE (Institute of Electrical and Electronics Engineers) in December 1965. By this time, three pairs of Velas had been launched, and the publication included unclassified data from all six satellites, providing evidence that the technology was operational.

In the introduction, the journal notes that “the dearth of published material on some aspects of nuclear test detonation has, in part, been the result of the security blanket under which much of the work has understandably been conducted.” To this day, a paper with this level of detail about a national security project is an anomaly.

Ian Strong remembers that his colleagues thought that publishing the Vela papers was a good plan. “The Russians had good scientists; we knew that,” he says. “They would be able to tell that those instruments would be able to detect a bomb.” And the plan worked. “The Russians never did cheat,” he says. “Never tested above ground after they said they wouldn’t.”

According to Eric Dors, program director for Intelligence and Emerging Threats, “There is an additional benefit that Vela and its science-based approach have delivered to the mission, which is science-based deterrence.” The concept of scientific superiority as deterrence is a major component of the Los Alamos mission.

“Part of the Laboratory is seen outside the fence (by the public),” says William Priedhorsky, program director of Laboratory Directed Research and Development, “and we want to be very clear about the excellence that is communicated that way, so that potential adversaries say, ‘Whatever they’re doing behind the fence (in secure areas) must be just as good, so let’s not mess with them.’”

These ties between research and national security continue to be integral to the culture of Los Alamos. “Over my 41 years at the Lab,” Priedhorsky says, “I have come to understand the great scientific breadth and strength of the Lab and how it contributes to the nation in so many ways. It has been the greatest honor of my lifetime to contribute a small piece to that.”

Descendants of Vela

The legacy of Vela continues at Los Alamos today. Data from Project Vela is still used for national security work at the Laboratory, and sensors continue to be an important part of nuclear detonation detection. “We’ve got basically a whole division of people working every day on designing, building, testing, and analyzing data from newer sensing payloads that go on satellites,” Kippen says.

Tess Light, who works on EMP sensor development and is chief scientist for space-based nuclear detonation detection, calls Vela “the mother, or perhaps grandmother” of her work. “We still list the Vela sensors in any timeline describing the evolution of our capabilities,” she says.

The history that began with Vela has been built upon over the years, resulting in “expertise in nuclear weapons, detector technologies, and the natural radiation background of space,” says Ben Norman, a project leader in the Space Science and Applications group. Such expertise makes Los Alamos “the perfect place to continue space-based treaty monitoring.”

A man, laying on the floor, stretches to reach a Vela satellite to perform a final check.
Laboratory researcher Richard Belian performs a final check of the Vela V-B satellite prior to its launch in April 1970. Vela V-B was the last of the Vela twin satellites launched as part of a program to improve the United States' capability to detect, locate, and identify nuclear explosions conducted in a variety of environments. Los Alamos National Laboratory

Los Alamos continues to be the premier lab for the development of these types of instruments. “The threat of what we’re searching for and monitoring is changing,” Kippen explains, “and it takes a nuclear weapons development lab to understand that, which is another example of why Los Alamos is the place to do this.”

Currently, Los Alamos has seven satellite instruments for varying purposes in various stages of production, and usually one or two Laboratory instruments are launched each year. For example, nuclear detonation detection sensors go on every single GPS satellite and a number of geostationary satellites.

Nuclear detonation detection, Kippen says, “is still our biggest footprint in the space business. We do other things now in space, but 60 percent of the space activities at the Lab are still on this program that began with Vela.” Just as the science of weapons evolves, so does the science of detection. Who is testing and where is still vitally important to U.S. national security. That work still requires advanced research, and the need to be accurate and reliable is of paramount importance. “We need to be able to say, yes, absolutely, it was a nuclear explosion” so the United States can “act accordingly,” says Brian Dougherty, a project leader in ISR Division.

Los Alamos and Sandia are currently preparing a set of experiments for the next generation of nuclear detonation detection sensors. “In many ways, these experiments hearken back to Vela,” Kippen says. “It’s putting things in space that have never been done before. It’s our most ambitious experimental program in many years.” SENSER (Space and Endoatmospheric NuDet [Nuclear Detonation] Surveillance Experimentation and Risk Reduction) is an experimental testbed for many new sensing technologies and modalities that are being considered for future use. Set for launch in 2021, the experiment will put sensing modalities for x-rays, gamma rays, neutrons, and radio frequency and optical signals all on the same satellite for the first time since the launch of the last six Vela satellites.

A group of six people kneeling behind electronic equipment.
The Laboratory is home to the team for the Space and Atmospheric Burst Reporting System (SABRS), part of the United States' system for space nuclear detection. Los Alamos National Laboratory

Between 1963 and 1970, Project Vela yielded six launches, each with twin satellites. In addition to the data they provided for nuclear detonation detection, the satellites enabled a host of other scientific research projects, including Ray Klebasadel’s historic discovery of gamma-ray bursts, a phenomenon that sparked decades of astrophysics debates among scientists, including Edward Teller and Stephen Hawking. “Vela’s impact,” says Light, “caused Los Alamos to become a major player in space research and engineering.”

Project Vela continues to inspire not only technical accomplishments, but also a continuation of the spirit of discovery, ingenuity, and national pride that sparked its development. “The treaty monitoring mission imparts a real sense of importance,” says Caleb Roecker, an early-career scientist in ISR. “I truly believe what we do in ISR affects the nation and keeps us safe.”

Katherine Mesick, also an early-career ISR scientist, agrees. “Vela demonstrates the Laboratory’s abilities to rapidly provide technical solutions to challenging problems,” she says. “This is an extremely important mission, and I am excited to be a part of continuing the Vela legacy.”

In September of 1984, though it was still functioning, the last Vela satellite was turned off. And though they no longer gather data, all 12 Vela satellites are still in orbit as, below them, Los Alamos carries on the work they began.