In 1964 intelligence reports kept indicating that China was preparing to test a nuclear bomb at its Lop Nor nuclear installation in Xinjiang. On October 16, 1964 China tested a nuclear weapon in Xinjiang. It was expected but not enough details were known. Later in November 1964, the CIA launched a U2 flight out of Aviation Research Centre (ARC)’s Charbatia Air Base in Orissa, but its return turned out to be a bit of a mishap. The U2 overshot the runaway and got stuck in slushy ground caused by heavy rain in the monsoons.
Getting it unstuck and out of India without being noticed by the Indian press, then even much more subject to leftist influences and hence antagonistic to the USA, was another clandestine operation. This gave all concerned quite a scare and it was decided to rely on other technical means. So CIA decided to launch an ELINT operation along with R&AW and ARC to track China’s nuclear tests and monitor its missile launches.
The operation, in the garb of a mountaineering expedition to Nanda Devi involved celebrated Indian climber M S Kohli who along with operatives of Special Frontier Force and CIA (most notably Jim Rhyne, a veteran STOL pilot), was to place a permanent ELINT device, a transceiver powered by a plutonium battery, that could detect and report data on future nuclear tests carried out by China. The plan to install a snooping device was hatched far away in Washington D.C., in the offices of the National Geographic Society. Barry Bishop, a photographer with the magazine, interested Gen. Curtis LeMay of the US Air Force in the idea.
The actual efforts called for to place a permanent electronic intelligence (ELINT) device powered by a nuclear SNAP 19C power pack fuel cell. The first attempt to place this device on the Nanda Devi, by a Kohli-led SFF team under the cover of a mountaineering expedition failed as the team had to retreat in the face of adverse conditions and left the device in a small unmarked mountain cave after having hauled the device to just short of the 25,645 feet peak. When another Kohli-led expedition returned the following year to recover the device, it was found to be missing. 
In the meantime the Chinese not only kept testing nuclear weapons at regular intervals but also ballistic missiles. The urgency to gather information was never greater. Another mission was launched in 1967 to place a similar device on the Nanda Kot. This mission was successful but a couple of years later another problem cropped up; snow would pile up over the antenna and render it blind. So Kohli and a SFF team were sent once again to bring it down, this time they retrieved it successfully.
In October 1967 the Chinese began testing an ICBM capable of reaching targets 6000 miles away. There was renewed urgency to find out more. So SFF mountaineers went off on one more mission in December 1969 to successfully place a gas powered device on an undisclosed mountain supposedly in Chinese controlled areas. But by the following year, the US had the first generation of the TRW spy satellites in place and did not have to rely on the old ELINT devices.