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.

中文翻译：

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1979 年 9 月 22 日 Vela 事件：检测到的双闪

摘要 1979 年 9 月 22 日，美国卫星 Vela 6911 上的两个光学传感器检测到双闪光，这似乎是在南大西洋或印度洋上空进行的大气核爆炸的特征。它被称为船帆座事件、747 号事件或 747 号警报。第二个脉冲期间两个信号幅度之间的异常导致美国政府为评估该事件而成立的专家小组在 1980 年中期得出结论，认为一个更可能的解释是是一颗小流星体对卫星的撞击，这些碎片将阳光反射到传感器的视野中。没有提供模型来支持这一论点，并且在 Vela 检测到的所有已确认爆炸的第二个脉冲中给出了一个类似的异常（称为背景调制），尽管是后来开始的。尽管如此，这一事件一直是激烈辩论的主题。本文回顾了证据，并根据最近解密的文献以及行星际尘埃和超高速撞击的现代知识，对原始 Vela 信号进行了更新分析。鉴于卫星的几何形状，以及大部分表面由太阳能电池板组成，任何碰撞产生的大部分碎片都会被带离传感器的视野。因此，流星体碰撞的可能性比之前假设的要小得多。相反，双闪与核爆炸一致，尽管被老化的卫星检测到，背景调制异常和/或更早开始，也见于事后系统测试。