Calibration of the NCAR particle cameras

Particle cameras are flown on the NCAR/NOAA sailplane Explorer and the South Dakota School of Mines and Technology T-28 for taking in-situ photographs of cloud particles. The images are examined to determine particle phase (ice or water), structure, size distribution, and concentration. The two cameras have been described by Cannon (1974) and Stengel (1977), respectively. In order to obtain definitive information from these cameras, it is necessary to calibrate them by photographic particles of known composition and size at known distances from the lens. These calibrations are performed to determine the response of the camera to out-of-focus particles of various types as well as to identify distinguishing image characteristics of water drops, frozen drops, and frozen and melting ice particles. The employed techniques are described and the first results of the calibrations are presented.