Nearly 30 years later there still is no certainty that a flash detected by the sensors of an American satellite indeed signaled a nuclear test that, according to foreign publications, involved Israel.

In September 1979, a United States intelligence nuclear detonation detection source, a Vela type satellite, which covered the Indian Ocean, detected a flash several hundred kilometers off South Africa's coast.

In 1963, the United States, the Soviet Union and Britain had signed an agreement that partially banned nuclear tests - at sea, in the atmosphere and in space (though not above ground and underground). Since 1996, there has been a comprehensive treaty that bans nuclear tests at sea, in the air, in space and on the ground, to which Israel is a signatory.

The Vela type satellites were equipped with sensors to detect flashes of light and radioactive radiation characteristic of nuclear explosions. The flash of a nuclear explosion is very short and is picked up on two spectrums, those of regular light and gamma ray radiation, with a time span between one and the other. The assessment that the satellite had indeed detected a nuclear test was further backed by the fact that several days after that flash, a seismic monitoring station in the Philippines recorded maritime shocks.

Most of the experts in the American intelligence community (and others outside) thought at that time the signals detected by the satellite had pointed to a nuclear test. However, there was also a possibility of a "false alarm" due to a fault in the satellite's detection system.

To ascertain the facts, a secret committee was set up under then U.S. president Jimmy Carter. The committee, headed by Prof. Jack Ruina of the Massachusetts Institute of Technology, failed to reach a decisive conclusion.

Most of the committee's members assumed that South African navy vessels had sailed out of Simonstown port, near Cape Town, to a secret location in the Indian Ocean, where they conducted the nuclear test. The committee defined the nuclear facility tested as compact and, in an impressive way, especially clean, emitting little radioactive fallout. That is why it was so difficult to pinpoint the test. Another assessment concluded a cannon had fired a nuclear shell. In other words, the test focused on a tactical nuclear weapon.

The experts believed the test was carried out at sea because there was no better alternative. Some two years earlier a Soviet spy satellite, Cosmos, detected underground tunnels at the South African Vastrap nuclear test site in the Kalahari Desert. That indicated preparations for a nuclear test or a series of tests. The Soviets relayed the information to the Carter administration, which applied heavy pressure on the government of John Vorster to stop work at the site.

Most of the examination team assumed there had been a joint Israeli-South African test. Another intelligence assessment said it was solely an Israeli test. A third assessment, published at the time, said that even if it was not a joint test, scientists of the Israel Atomic Energy Commission and of the nuclear reactor in Dimona, had been aboard one of the escort ships during the test and examined the results. On February 20, 1980, the CBS TV network broadcast an item about the test, saying the two states had carried it out and reported the American administration was looking into it.

South Africa began developing its nuclear program in 1949. To do so, it used know-how, equipment, technology and reactors used for research and for power that it bought from the United States, Britain, France and Germany. However, in 1976, the Western countries halted their nuclear ties with South Africa after discovering the Apartheid regime had begun to develop a military nuclear power under the guise of a peace program. According to foreign reports, that is when the nuclear cooperation between the Apartheid regime and Israel intensified. According to those reports, there were exchanges of information and reciprocal visits by the two states' atomic energy commissions.

It was reported, inter alia, that Prof. Ernst David Bergman, who headed the Israel Atomic Energy Commission, visited South Africa along with another senior official, Shalheveth Freier, and the two had been the guests of the atomic energy commission there. Other reports said that as early as the 1960s Israel bought natural uranium from South Africa and later provided it with tritium, a radioactive isotope of hydrogen that is essential to amplify the power of a nuclear bomb and to produce a hydrogen bomb.

Israel and South Africa vigorously rejected the reports of nuclear cooperation between them and in particular denied a joint nuclear test. Similar denials were made some 13 years later, in March 1993. Then, for the first time, Frederik Willem de Klerk, who was the state's president who dismantled the Apartheid regime, acknowledged that South Africa had developed a nuclear weapon.

Some time before, de Klerk's government reported the history of its nuclear development to the International Atomic Energy Agency in Vienna and opened its nuclear program and facilities to the agency's inspectors. In September 1993, the agency published a document summarizing the main points in the stages of South Africa's nuclear development. While the document is not complete, it is considered the best such information available. It states that between 1981 and 1989, South Africa's nuclear scientists made six nuclear weapons. The seventh was in the final stages of production. In 1990, after it was decided to transfer the regime to the black majority, the government closed its enriched uranium plant, destroyed the seven nuclear weapons and placed all the excess material and nuclear waste under the IAEA's supervision.

Unlike Israel, South Africa became a signatory to the Non-Proliferation Treaty in 1991 and accepted the International Atomic Energy Agency's supervision.

The nuclear weapons that South Africa developed were of the "gun type." It is very outdated technology, said the South Africans in a statement. The more advanced bombs that the nuclear powers have are of the "implosion type."

According to the press abroad, Israel had warheads commensurate with the most advanced technology in the world. The implosion-type bomb can be launched from a missile or a cannon. A gun-type nuclear weapon is launched from an aircraft only.

The South African gun-type bomb weighed about a ton. It was 1.8 meters long, and its diameter was some 650 millimeters. The power of such a bomb was equivalent to the one dropped on Hiroshima.

The South African announcement and similar statements that de Klerk had made noted that South Africa developed nuclear devices without the help of any foreign state. It also said South Africa "never carried out a nuclear test, not in the atmosphere nor underground. Nor was South Africa involved in any other country's nuclear test."

However, in 1997, Aziz Pahad, the deputy minister of foreign affairs in Nelson Mandela's government, confirmed to me that the 1979 flash was "definitely a nuclear test." He confirmed, moreover, that "the nuclear issue was secret, and that many documents were destroyed although not all of them. There are many reports of relations between the two states' scientists and cooperation regarding very specific equipment."

Gen. Constand Viljoen, an Afrikaner pillar of the Apartheid regime who commanded South Africa's ground forces from 1976 to 1980 and then was chief of general staff for five years, said: "We wanted to get nuclear know-how from anywhere we could and from Israel, too." Viljoen said: "That is what was decided, and that is how we acted."

Viljoen, who visited Israel and conferred with senior officers, said he had opposed his country's nuclear program as a waste of money and resources. "Instead of the billions we spent on nuclear weapons," he said, "we could have bought tanks and needed military equipment. Ambitious politicians and the heads of the Armscor arms corporation [where the nuclear weapons were developed - Y.M.] pushed for the program. As a good soldier I was compelled to obey them." Viljoen evaded a question about the 1979 test.

Israel never acknowledged it has nuclear weapons. That is why it cannot admit it carried out a test, that it took part in another country's test or that it helped carry it out. However, various publications and American documents indicate that in 1969, then prime minister Golda Meir reached a secret understanding with the then U.S. president Richard Nixon: The United States agreed to cease its weak supervision over the nuclear rector in Dimona, which has been going on since 1961, and in exchange Israel undertook not to carry out a nuclear test.

Since 1945, members of the nuclear club have carried out more than 2,000 nuclear tests. Of those, 150 have been defined as tests "for peaceful purposes." The United States leads the list with 1,032 tests; followed by the Soviet Union with 715 tests; France, 210; and Britain and China with 45 tests each. India carried out three tests (one of them, in 1974, for "peaceful purposes"). In the last three years North Korea conducted two tests.

Can a state produce an operational nuclear weapon without testing it? Yes, say the experts, adding that today, with powerful computers that can accurately simulate nuclear tests, it is definitely possible to avoid an actual test.

Another possibility is that a state that has developed nuclear weapons compensates for the absence of a nuclear test by receiving or otherwise obtaining the results of a test another country has conducted. If Israeli representatives had been in South Africa in 1979 just as observers, examined the results of the tests or got them, then Israel could argue it has abided by its agreement with the United States and still benefit from extensive information about a nuclear test, avoiding the need to conduct one of its own.