On 22 September 1979 around 00:53 GMT, the Vela 6911 satellite detected the characteristic double flash of an atmospheric nuclear explosion apparently over the Indian Ocean or South Atlantic. The test location was later localized at 47 deg. S, 40 deg. E in the Indian Ocean, in the vicinity of South Africa's Prince Edward Island, by hydroacoustic data. Due to the position ambiguity of the initial detection (the Vela optical sensors were not imaging sensors and could did not detect location), the location is variously described as being in the Indian Ocean or South Atlantic. The characteristics of the light curve indicated that it was a low kiloton explosion (approximately 3 kt). The hydroacoustic signal indicated a low altitude explosion. A major and lingering controversy erupted over the interpretation of this apparent detection.
The Vela satellite program was an nuclear detonation (NUDET) detection system setup after the 1963 limited test ban and was designed to detect nuclear explosions in space and (later) air. There were two groups of Vela satellites developed. The original Vela were equipped only with sensors for space detection and were launched in three pairs between 1963 and 1965. They operated for at least five years, far beyond their nominal design life of six months. A second generation called Advanced Vela were launched in 1967, 1969 and 1970. These satellites added "bahngmeters" - optical sensors for detecting atmospheric tests - and had a nominal design life of 18 months, but were later rated with a seven year lifespan, although they were all operated for more than ten years, with the last one being turned off in 1984 -- after 14 years of successful operation [JPL 2001]; [Astronautix 2001].
Vela 6911 is presumably one of the Advanced Vela pair launch launched on 23 May 1969 (perigee 77,081 km, apogee 145,637 km, inclination 61.6 deg), and had thus been operating over ten years at the time of the 1979 detection.
The Vela satellite system had previously made 41 similar detections of atmospheric tests, each of which had been subsequently confirmed through other means. The detection came at a bad time for the Carter administration which would be under pressure to take definite action if the detection were accepted as accurate. Inescapably it seemed that either Israel, South Africa, or both, would be implicated. Consequently a panel of scientists from academia known as the Ruina Panel, after its head Dr. Jack Ruina, was created to review the reliability of the Vela data. Since this satellite was operating past its expected lifespan, and its electromagnetic pulse (EMP) sensor was inoperative, questions about the reliability of the detection were raised. The panel ultimately concluded in a report released in the summer of 1980 that the signal
"was probably not from a nuclear explosion. Although we cannot rule out that this signal was of nuclear origin".This conclusion has cast a pall over public confidence in the ability of the U.S. to unambiguously detect clandestine nuclear explosions for over twenty years.
The instruments used by the Vela satellites for detecting atmospheric nuclear explosions are called "bhangmeters". These are optical sensors that record light fluctuations on a sub-millisecond time scale. All atmospheric nuclear explosions produce a unique and easy to detect signature: an extremely short and intense flash, followed by a second much more prolonged and less intense emission of light. The initial flash is typically 1 millisecond long, and although it emits only about 1% of the total thermal energy of the fireball, it is actually the point of maximum brightness for the fireball. The second peak may take from hundreds of milliseconds to several seconds to develop, depending on the size of the explosion, and lasts a comparable period of time.
This phenomenon occurs because the surface of the early fireball is quickly overtaken by the expanding hydrodynamic shock wave. This shock wave acts as an optical shutter, hiding the small but extremely hot and bright early fireball behind an opaque ionized shock front which is comparatively quite dim.
No natural phenomenon is known that can imitate this signature. In fact it is reported that no false alarms have ever been detected with a Vela bhangmeter. Every other double-flash detection has later been confirmed to be an actual nuclear test.
According to Seymour Hersh, the idea of referring this detection to an advisory panel was floated before any potential problems with the detection had been noted. An urgent meeting to discuss the handling of this event was held in the White House situation room soon after the intelligence report on the incident reached the Oval Office.
Among those attending were National Security Advisor Zbigniew Brzezinski, his aide for global issues Gerald Oplinger, deputy director of the Arms Control and Disarmament Agency Spurgeon Keeny, and Presidential Science Advisor Frank Press. At this meeting the probability of a nuclear test was placed at 90 percent or better. Either Keeny or Press (accounts of the participants vary) suggested convening a panel - at least as much as a delaying tactic as an effort to ensure that the data was carefully evaluated [Hersh 1991].
There is no question that a confirmed detection of a nuclear test would have put the Carter administration in a very difficult position. President Carter had placed great emphasis on nuclear non-proliferation. The administration had been a troubled one, with the recent collapse of a major ally in the Middle East (Iran) as one of many problems. The upcoming re-election campaign was certain to be an uphill battle. If Israel were to be linked to a nuclear test (as seemed likely, it it was real) the political damage from imposing sanctions, or not imposing sanctions, would likely be severe....
Prime Minister F.W. de Klerk announced in March 1993 that South Africa had built nuclear weapons, and since that time additional information has periodically come forth. It was revealed that SA had indeed developed and manufactured nuclear weapons (gun-type devices using highly enriched uranium) but no tests (beyond a single zero-yield lab test) were disclosed. The information that was made available tended to disconfirm the hypothesis that South Africa conducted the test. The IAEA has apparently been able to confirm that whatever discrepancies exist between South Africa's HEU inventory and its production records (and some are inevitable) the amount is too small to hide the HEU required for a test. Further, South Africa's accounts of its weapon development activities indicate that its first device was not complete until months after the incident. From documents made available to it, the IAEA believes that the first nuclear device was not manufactured until November. This first device was an experimental one named "Melba" which was said to be kept for research and demonstration purposes throughout the program (which ended in 1989).
Speculation on who "might" have conducted the test was
* it was a South African test,
* it was an Israeli test,
* it was a joint South African-Israeli test.
http://nuclearweaponarchive.org/Safrica/Vela.htmlThe Vela Incident (sometimes known as the South Atlantic Flash) was the possible detection of a nuclear weapon test by an American Vela satellite on September 22, 1979. Much of the information about the event is still classified.
The flash was detected by one of the American Vela satellites developed to detect nuclear explosions. On 22 September 1979 at 00:53 GMT, the Vela 6911 satellite detected the characteristic double flash of an atmospheric nuclear explosion of some two to three kilotons apparently over the Indian Ocean or South Atlantic between Bouvet (a dependency of Norway) and the Prince Edward Islands (47S, 40E), a dependency of South Africa.
Vela 6911 was one of the pair launched on 23 May 1969, over ten years before the possible explosion. It was operating two years past its designed lifespan and its electromagnetic pulse (EMP) sensor had failed. It had also developed a fault in July 1972 where around half a second of its recording memory had failed. This had cleared itself in March 1978.
It is still uncertain whether the satellite's observations were accurate. After the blast was detected the Carter administration summoned a panel of experts who in early 1980 found that the report was likely erroneous, caused by a malfunction in the satellite. Most outside observers doubt this assertion.
The panel set up to review the evidence, the Ruina Panel, released its report in summer of 1980 and concluded that the signal "was probably not from a nuclear explosion. Although we cannot rule out that this signal was of nuclear origin". It proposed that the satellite was in error and had perhaps been hit by a small meteorite. That the explosion was only picked up by one of the satellites seems to support their assertion. US Air Force flights in the area soon after also failed to detect any sign of radiation.
Many doubt the panel's findings, arguing they were politically motivated. A considerable amount of evidence corroborating the nuclear hypothesis has been gathered. The Vela satellites previously detected 41 atmospheric tests, each of which had been subsequently confirmed through other means. There was some other data that seemed to confirm the explosion.
Hydrophones operated by the US Navy detected a signal which was consistent with a small nuclear explosion on or slightly under the surface of the water near Prince Edward Island. The radio telescope at Arecibo, Puerto Rico also detected an anomalous traveling ionospheric disturbance at the same time. A test in Western Australia conducted a few months later found increased radiation levels. The Los Alamos scientists who worked on the Vela program remain convinced that their satellite worked properly.It has also been proposed that there was an explosion, but one caused by a comet or other natural cause.
The two potential sources of an unexplained nuclear blast were Israel and South Africa, both of which had covert nuclear weapons programs at the time. A test by either Israel or South Africa would have been very awkward for the Carter administration. Israel was a close American ally, while the South African relationship was a close but unpopular one. Carter had worked hard on nonproliferation issues, and a vigorous response would have been required if it had been proven that either nation had conducted the test. This would have disrupted the negotiations underway over the Camp David Accords.
If a nuclear explosion did occur it is also uncertain who triggered it.
There are difficulties with both the South African and Israeli hypothesis. South Africa did have a nuclear weapons program at the time, and the geographic location of the tests points to their involvement. However, since the fall of apartheid South Africa has disclosed most of the information on its nuclear weapons program which point to South Africa not having the ability to mount such a test in 1979. However, in 1977, Soviet satellites reported a possible test site in the Kalahari desert which was then dismantled. For South Africa to have carried out the tests a good number of the documents released would have to be forgeries.Israel almost certainly had nuclear weapons in 1979, but it is questioned whether they had the capability to mount a covert test thousands of kilometers away. If it was an Israeli test it is almost certain that there was South African cooperation. Potentially the test was of an Israeli weapon but organized by South Africa.
It is unlikely any of the declared nuclear powers would have conducted such a test. They had little reason to conduct tests covertly (as all had standing traditions of overt nuclear testing except for India), and the small size of the blast might reflect a less advanced weapon (though there are many "advanced" reasons for small tests as well, including tactical nuclear weapons and testing the primary devices for thermonuclear weapons). The only other potential partner for South Africa sometimes mentioned is
Taiwan.
http://en.wikipedia.org/wiki/Vela_IncidentSome type of non-nuclear test, perhaps a zero yield or implosion test, occurred on 2 November 1966 [possibly at Al-Naqab in the Negev].
There is no evidence that Israel has ever carried out a nuclear test, although many observers speculated that a suspected nuclear explosion in the southern Indian Ocean in 1979 was a joint South African-Israeli test.
At precisely 0100 GMT [other sources claim 00:53 GMT] on 22 September 1979, sensors aboard the VELA 6911 satellite detected two closely spaced flashes of light. The event apparently occured over the Indian Ocean at 47 deg. S, 40 deg. E in the Indian Ocean, near South Africa's Prince Edward Island. The most obvious explanation was that someone had detonated an atomic bomb. The list of suspects quickly narrowed to South Africa and Israel.
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.
http://www.globalsecurity.org/wmd/world/israel/nuke-test.htm