This is an article excerpted from the LASL Daily Newsbulletin of Friday, July 11, 1997.

To the Daily News Bulletin at Los Alamos

Friday, July 11, 1997

Blast from the past: Lab scientists receive vindication

Significant events in 1979: the Shah left Iran, the Three Mile Island reactor suffered a partial core meltdown, and a clandestine nuclear test off the tip of South Africa was detected by an aging satellite, Vela 6911.

Two of those world events made headlines, one remained both a partial mystery and an ongoing controversy until this year.

In an April 20 article that appeared in the Israeli Ha'aretz Daily Newspaper, South African Deputy Foreign Minister Aziz Pahad confirmed for the first time that a flare over the Indian Ocean detected by an American satellite in September 1979 was from a nuclear test. This statement was confirmed by the American Embassy in Pretoria, South Africa, as an accurate account of what Pahad officially acknowledged. The article said that Israel helped South Africa develop its bomb designs in return for 550 tons of raw uranium and other assistance.

Eighteen years have passed since the flash was picked up by the Vela satellite. With Pahad's revelation, Laboratory scientists say, this controversy can at last reach closure. Original analyses conducted by Lab scientists and others in the U.S. intelligence community said the flash could only be from a nuclear test. Now, their studies have been vindicated.

In 1979, the same analyses had been vigorously challenged by the Carter administration. The challenge was driven by a general mistrust in aging satellites and an unwillingness to accept the efficacy of other evidence. Instead, the Carter administration assembled a panel of scientists from academia to review the data. After their review, the panel concluded that, lacking independent collaborative data to support a nuclear origin of the signals, the original interpretation of the satellite data could not be justified.

The panel said the flash could have been caused by a combination of natural events, specifically a micrometeorite impact on the detector sunshade, followed by small particles ejected as a result of the impact. But Los Alamos scientists were not dissuaded.

"The whole federal laboratory community came to the conclusion that the data indicated a bomb," said Dave Simons of Nonproliferation and Arms Control Research and Development (NIS-RD). "But in the administration's view, because the evidence was weak, they took exception to the information and our analysis."

"It was unsettling because we were quite thoroughly convinced of our interpretation," Simons said.

The Vela satellites were deployed in support of the Limited Test Ban Treaty of 1963 and carried sensors designed at the Lab and Sandia National Laboratories to detect nuclear explosions in the atmosphere and in space. The satellites were launched in pairs beginning in 1963. The last and sixth pair was launched in 1970. Each satellite carried two optical sensors, called bhangmeters, to view Earth and detect atmospheric nuclear explosions associated with unique, telltale signatures of brief, intense light pulses. The satellites also carried an electromagnetic pulse sensor.

One of the problems with the Vela's optical data was that one sensor detected more light than did another, more sensitive one. The discrepancy suggested to the White House-assembled panel that the bhangmeters saw an event close at hand, perhaps sunlight glinting off a bit of meteor debris that had bounced against the satellite. The panel maintained their conclusions even though similar discrepancies had been observed in Vela signals from previous confirmed atmospheric nuclear tests.

In addition to the very bright optical signals, an atomic explosion also unleashes a pulse of radiation at radio wave frequencies which can be detected by EMP sensors. This electromagnetic pulse covers much of the radio wave spectrum.

Other radiation emitted by the blast includes gamma and beta rays and neutrons, which, in the case of a sea level or low-altitude explosion, are absorbed by the atmosphere giving rise to electromagnetic radiation at frequencies extending over the entire range from radio waves to the ultraviolet. Detectors on satellites are capable of sensing at least some of these instantaneous signals, but if the radiation is missed in the first instant, then they are gone forever, traveling away from Earth at the speed of light.

Although its optical sensors were still functioning, the Vela satellite that detected the 1979 blast was operating beyond its seven-year life span. Because of the satellite's age, the EMP sensor was not operating.

After the detection of the September 1979 event, the United States government quickly launched a major effort to collect corroborating evidence that focused on finding radioactive bomb fission products in the environment. But the sampling attempts never entered the low pressure air mass that had been over the location of the time of the explosion. While low levels of iodine-131, a short-lived radioactive fission product, were detected in sheep thyroids in western Australia, these results were also questioned.

In addition to detection satellites, the United States maintains a global network for detecting other atomic explosion phenomena, including sound waves, seismic shock waves traveling through Earth, and hydroacoustic pulses traversing Earth's oceans. Of these, the best data were from the hydroacoustic signals collected on devices called hydrophones. The hydrophone data indicated signals both from a direct path and from a reflection of the Antarctic's Scotia Ridge. Analyses of these signals conducted by the Naval Research Laboratory confirmed that they had been generated at a time and location consistent with the Vela 6911 detection and that their intensity was consistent with a small nuclear explosion on, or slightly under, the ocean's surface.

More evidence came from a Lab researcher using a radio telescope for an unrelated project in Arecibo, Puerto Rico, detected a traveling ionospheric disturbance - a ripple in Earth's upper atmosphere - moving south to north during the early morning hours of Sept. 22, 1979, something researchers had never before witnessed.

But such evidence was discounted by the White House panel.

In 1979, the South African government adamantly denied the test. Former Foreign Minister Roelof Botha said he knew nothing of the blast and suggested the American government question the Chinese or Russians. But Botha stopped short of saying that South Africa had not detonated a bomb or that the country had no intention of acquiring nuclear weapons.

The flurry over the issue exemplified American nervousness in world affairs, Botha added.

However, Lab scientists remained convinced that the flash was a nuclear detonation and invested substantial effort in analyzing the signal. Subsequently, Lab researchers published an unclassified paper describing the characteristics of optical signals caused by nuclear explosions.

In February 1980, CBS News was the first to suggest that Israel helped South Africa conduct a nuclear test. CBS received information from "informed sources," but until now, no South African government official was willing to lend the report any credibility.

Today, Lab scientists are worried that current satellites may have similar credibility problems in detecting atmospheric tests because of their ages. And for the next generation of satellites, the Pentagon has not decided whether budget cuts may affect decisions to place EMP sensors on detection satellites to be launched after the year 2000.

The Laboratory and the Department of Energy have spent nearly $50 million to develop the next generation of sensors and officials are hopeful they will be included in the payload of future satellites.

Researchers say that because the detection ability for underground and undersea tests is so good, today's rogue nations may choose to conduct clandestine atmospheric nuclear tests which is a good reason to include the EMP sensors on future satellites.

For the 1979 South African test, Los Alamos scientists are convinced that a functioning EMP detection system on the Vela satellite would have provided an unambiguous corroboration of their conclusion: the mystery optical flash of Sept. 22, 1979, was a nuclear explosion.

Ironically, researchers say, one of the most compelling recommendations of the 1979 White House panel is, today, in jeopardy of being overlooked. The panel said that because of the ramifications and possible consequences of nuclear explosions, it is imperative that systems be developed and deployed to provide prompt, reliable corroboration of the evidence.

--Kathy DeLucas