CAPS — Cloud, Aerosol, and Precipitations Spectrometer (CAPS, Manufacturer: DMT)

Second generation Cloud, Aerosol, and Precipitation Spectrometer (CAPS)

Aerosol particle and cloud hydrometeor size distributions (0.5 μm < Dp < 930 μm), particle optical properties, particle shapes, liquid water content, aircraft velocity

The CAPS is a combination of an optical particle spectrometer (named CAS) and a shadow imager (named CIP). It is equipped with additional sensors for liquid water content (LWC), airspeed, relative humidity and temperature.

The CAS operates with a laser at 658 nm and collects light scattered by individual particles to an angular range from 4.2° to 13.2° (forward detector) and to the angular range from 168° to 176° (polarization-sensitive backward detectors). The CAS is sensitive to particles in the diameter range from nominally 0.5 µm to 50 µm. The polarization of the backscattered light gives an indication for the particle shape.

The CIP uses light from a 658 nm collimated laser beam and detects particle shadows with a linear array of 64 optical diodes.  The diode resolution is 15 µm and the covered particle size ranges nominally from 15 to 930 µm. The diode array of the CIP instrument records shadows in three intensity levels and provides greyscale images of the measured aerosol and cloud particles.