First of all, let's clarify one thing. It was not a nuclear weapon that was lost. It was a nuclear-powered device that contained a specific isotope of plutonium. Not the isotope that is used in nuclear weapons but its plutonium-238 that were contained in this device. North of Nanda Devi you have Chinese occupied Tibet and further north you have Chinese occupied Xinjiang. Now in Xinjiang, present day China, there is a place called Lop Nur, which is where the Chinese in the 20th century tested their nuclear weapons. It is about 1500 Km far away from Nanda Devi. In 1964, China tested its first nuclear device in Lop Nur in the Chinese occupied Xinjiang and that was a matter of concern for the United States. The Americans then convinced India to set up a signals intelligence station in northern India on the Nanda Devi peak or near the peak of the mountain from which we can look far into China. We can see that the Nanda Devi mountain is about 8 km sea level and from that vantage p...