Cloud Imaging Probe (CIP)

Shadow images of particles passing through a collimated laser beam is projected onto a linear array of 64 photodetectors. The presence of a particle is registered by a change in the light level on each diode. The registered changes in the photodetectors are stored at a rate consistent with probe velocity and the instrument’s size resolution. Particle images are reconstructed from individual “slices,” where a slice is the state of the 64-element linear array at a given moment in time. A slice must be stored at each time interval that the particle advances through the beam a distance equal to the resolution of the probe. Optional greyscale imaging gives three levels of shadow recording on each photodetector, allowing more detailed information on the particles. The CIP also contains a Hotwire LWC sensor. This sensor estimates liquid water content using a heated sensing coil. The system maintains the coil at a constant temperature, usually 125 °C, and measures the power necessary to maintain this temperature. More power is needed to maintain the temperature as droplets evaporate on the coil surface and cool the surface and surrounding air. Hence, this power reading can be used to estimate LWC. Both the LWC design and the optional PADS software contain features to ensure the LWC reading is not affected by conductive heat loss.