MASC

The multi-angle snowflake camera (MASC) consists of three commercial cameras separated by angles of 36 degrees. Each camera’s field of view is aligned to have a common single focus point about 10 centimeters distant from the cameras. Two near-infrared emitter pairs are aligned with the camera’s field of view within a 10-angular ring to detect hydrometeor passage, with the lower emitters configured to trigger the MASC cameras. The sensitive IR motion sensors are designed to filter out slow variations in ambient light. Fallspeed is derived from successive triggers along the fall path.

The camera exposure times are extremely short, in the range of 1/25,000th of a second, enabling the MASC to capture snowflake sizes ranging from 30 micrometers to 3 centimeters. Any number of images, from zero to thousands, may be collected in a single day. These images are recorded in threes, one for each camera. They show monochrome (black and white) views of hydrometeors separated by 36 degrees.

Particle images acquired by the MASC can support the analysis of solid hydrometeors’ microphysical characteristics with an emphasis on precipitating snow crystals.

• Hydrometeor fall velocity
• Hydrometeor image