 Between 10 January and 6 February 1956, a total of 516 high-altitude vehicles were launched from the five different launch sites Gardermoen, Norway; Evanton, Scotland; Oberpfaffenhofen and Giebelstadt, West Germany; and Incirlik, Turkey;  54 were recovered and only 31 provided usable photographs.Numerous balloons were shot down or blown off course, and the flights led to many diplomatic protests from the target countries.MiG fighter pilots learned that at sunrise the balloons had dipped into shooting range because the balloons floated to a lower altitude as in the colder night air, the lifting gas cooled and became denser, reducing lift, so the balloons descended to lower altitudes where the air was denser.