When I say I discovered, it was really Robert Hastings, writing in his new book UFOS and Nukes: Extraordinary Encounters at Nuclear Weapons Sites. I have just applied an interesting paragraph from that book to what we know about Mogul and the secrecy around it.
Remember, the Mogul experiments began in New Mexico in early June and ended in September 1947. Stories about the balloon flights appeared in many newspapers beginning on July 10, just days after the officers at Roswell announced they had "captured" a flying saucer.
Hastings wrote, "In September 1947, Army Chief of Staff General Dwight D. Eisenhower directed the Army Air Corps to undertake the Constant Phoenix program, an on-going series of long-distance flights designed to detect atomic explosions ‘anywhere in the world.’ This high-priority activity was continued by the newly-created U.S. Air Force and, on September 3, 1949, radiation sensors abroad a USAF B-29 flying between Alaska and Japan confirmed the detonation of the first Soviet atomic bomb - some five years earlier than expected."
In other words, Mogul, to monitor Soviet atomic development was scrapped because a better method was found. Aircraft could maintain a constant level and could remain on station for hours at a time. A drifting balloon array moved with the vagaries of the winds and the sun (sun light could heat the balloon envelopes causing them to rise during the day). An aircraft could stay in virtually one place and when it needed to return for fuel or crew rest could be replaced in the same place by another aircraft.
At this point, Mogul was of no use. The secrecy requirement was gone. The original purpose, to spy on the Soviets wouldn’t be mentioned but the project no longer had the importance it once had. And, of course, with the deployment of spy planes and later satellites, the spying took on a much more sophisticated aspect than hanging some microphones on a balloon to drift over the Soviet Union.
With the collapse of the Soviet Union, and with everyone knowing that there are dozens of spy satellites up there photographing everything down here, there was no need to keep the Mogul secret, so the Air Force trotted it out to explain the Roswell crash debris. Mogul was a high priority project, they say. It was top secret, they say. But in the end, it was just a bunch of balloons tied together, sometimes with microphones attached and sometimes not. Nothing unusual to fool ranchers, Army officers, sheriffs or anyone else who might have found the remains of Mogul.
For those interested in more of what Robert Hastings has reported, you can only order UFOs and Nukes: Extraordinary Encounters at Nuclear Weapons Sites at ufohastings.com.