At the height of the Cold War*, President Eisenhower authorized "Project Genetrix." Project Genetrix involved the release of weather balloons over the Soviet Union, Eastern Europe, and China which were equipped with cameras which would automatically take photos during the daylight hours. The 200-foot tall balloons normally flew at 50,000 feet (15,000 meters) to 100,000 feet (30,000 meters) high and were generally out of the range of fighter aircraft. They and their photographic treasure trove would be recaptured by specially-equipped US aircraft after the balloons had soared over the enemy country.
The balloons and gondola were very flimsy and invisible to radar. Or so the Americans thought. Unfortunately, one of the steel support rods was 91 centimeters long, which happened to be the same wavelength as a frequency used by Soviet early warning radar. As a result, the balloons popped up on Russian radar screens as conspicuously as Barack Obama at an NRA convention.
The Soviets were very irritated and implemented the usual diplomatic blustering. They also quickly realized that the balloons at sunrise, after a cold night's flight, could be found at a lower altitude within the range of their MiG fighters. As a result, after less than a month, Eisenhower cancelled the project when only 54 out of 516 balloons were able to be retrieved by the Americans. Out of those 54 balloons, only 31 provided usable photos.
The project was not a total bust, however--at least from the viewpoint of the Soviets. Upon recovering the cameras from the balloons that they shot down, they discovered how the Americans had made temperature-resistant film which was also immune to external radiation. This enlightenment resolved a problem the Russians were encountering in designing their space program.
High-altitude reconnaissance by the USA resumed with its U-2 program, which ultimately resulted in its own set of political difficulties.
*From what I can tell, the "height of the Cold War" has been used to refer to virtually any date from the defeat of the Nazis in 1945 to the collapse of the Berlin Wall in 1989. Project Generix ran from January 10, 1956 to February 6, 1956.