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| 1 |
ID:
157473
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| Summary/Abstract |
On 22 September 1979 two optical sensors on U.S. satellite Vela 6911 detected a double-flash of light that appeared characteristic of an atmospheric nuclear explosion conducted over the southern Atlantic or Indian Ocean. It became known as the Vela Incident, Event 747, or Alert 747. An anomaly between the amplitude of the two signals during the second pulse led a U.S. government expert panel established to assess the event to conclude in mid-1980 that a more likely explanation was the impact of a small meteoroid on the satellite, the debris from which reflected sunlight into the sensors' field of view. No model was presented to support the contention, and a similar anomaly--known as background modulation--was a given for the second pulse of all confirmed explosions detected by Vela, though beginning later. Nonetheless, this event has remained the subject of intense debate. This article reviews the evidence and presents an updated analysis of the original Vela signal based on recently declassified literature and on modern knowledge of interplanetary dust and hyper velocity impact. Given the geometry of the satellite, and that the bulk of the surface comprised solar panels, much of the debris from any collision would be carried away from the sensors' field of view. Thus, a meteoroid collision appears much less likely than previously assumed. The double flash is instead consistent with a nuclear explosion, albeit detected by an aged satellite for which background modulation was abnormal and/or commenced earlier, also seen in post-event system tests. A companion paper to be published in 2018 presents radionuclide and hydroacoustic evidence supporting the conclusion that the Vela Incident was a nuclear weapon test explosion.
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| 2 |
ID:
124850
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| Publication |
2013.
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| Summary/Abstract |
This article investigates the possibility presented by De Geer (2012) that radionuclides detected at stations in South Korea, Japan, and Russia in May 2010 were evidence that North Korea conducted at least one unannounced low yield nuclear test on 11 May. It provides HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model) atmospheric transport modeling of the observed radionuclides assuming candidate origins in North Korea, ROK, Japan, Russia, mainland China, and Taiwan. Xenon activity calculations for reactor- and explosion-produced isotopes are used to ascertain possible release ratios and source terms. The HYSPLIT modeling finds that the most likely origin of the radionuclides is close to the site of North Korea's declared nuclear tests in 2006 and 2009. The activity calculations show that the source term is consistent with a nuclear test up to a few hundred tons yield. These results are discussed in the context of a decoupled but uncontained nuclear test by North Korea on 11 May 2010. If the scenario suggested by De Geer and supported here is correct, it seems that there is a significant possibility of detecting even a small, decoupled nuclear test in North East Asia using components of the International Monitoring System of the Comprehensive Test Ban Treaty.
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