John Glenn [Mercury Atlas 6]

“Over the Atlantic on the third orbit, Glenn photographed an overcast region to the northwest and patterns of scattered clouds in the foreground” (Pilot’s Flight Report, p.127).

“As I looked back at the Earth from space, colors and light intensities were much the same as I had observed when flying at high altitude in an airplane. The colors observed when looking down at the ground appeared similar to those seen from 50,000 feet. When looking toward the horizon, however, the view is completely different, for then the blackness of space contrasts vividly with the brightness of the Earth’s. The horizon itself is a brilliant, brilliant blue and white. It was surprising how much of the earth’s surface was covered by clouds. The clouds can be seen very clearly on the daylight side. The different types of clouds, vertical developments, stratus clouds, and cumulus clouds, are readily distinguished. There is little problem identifying them or in seeing the weather patterns. You can estimate the relative heights of the cloud layers from your knowledge of the types or from the shadows the high clouds cast on those lower down. These observations are representative of information which the scientists of the U.S. Weather Bureau Meteorological Satellite Laboratory had asked Project Mercury to determine. They are interested in improving the optical equipment in their Tiros and Nimbus satellites and would like to know if they could determine the altitude of cloud layers with better optical resolution. From my flight I would say it is quite possible to determine cloud heights from this orbital altitude. Only a few land areas were visible during the flight because of the cloud cover. Clouds were over much of the Atlantic,” related John Glenn (Flight’s Pilot Report).