At one point in the 1970s there were more than 1,000 people in the Danbury area working on The Secret. And though they worked long hours under intense deadlines, sometimes missing family holidays and anniversaries, they could tell no one - not even their wives and children - what they did. They were engineers, scientists, draftsmen and inventors. It was dubbed Big Bird'' and it was considered the most successful space spy satellite program of the Cold War era. From 1971 to 1986 a total of 20 satellites were launched, each containing 60 miles of film and sophisticated cameras that orbited the earth snapping vast, panoramic photographs of the Soviet Union, China and other potential foes. The film was shot back through the earth's atmosphere in buckets that parachuted over the Pacific Ocean, where C-130 Air Force planes snagged them with grappling hooks. The scale, ambition and sheer ingenuity of Hexagon KH-9 was breathtaking. So too is the human tale of the 45-year-old secret that many took to their graves. Hexagon was declassified in September. "The question became, how do you hide an elephant?'' a National Reconnaissance Office report stated at the time. It decided on a simple response: "What elephant?'' Employees were told to ignore any questions from the media, and never confirm the slightest detail about what they worked on.