A camera for photography of atomospheric particles from aircraft

A special camera has been installed on a research sailplane to take in situ photographs of atmospheric particles. Ice particle shapes, sizes, and concentrations; raindrop sizes and concentrations; and estimates of cloud droplet concentrations and maximum sizes are obtained from the photographs. The camera is capable of photographing particles as small as about 4 μ radius; the size of the largest particle completely imaged is limited by the 24×36 mm projected area photographed. Liquid particles can be distinguished from ice particles for radii greater than 50 μ. Techniques are described for calibrating the camera so that both in-focus and out-of-focus images are used for obtaining concentration and size data. Examples of photographs of ice particles, raindrops, and cloud droplets are shown. Camera improvements for getting more data for a given length of flight are suggested.