Use of Rotating Pinholes and Reticles for Calibration of Cloud Droplet Instrumentation

Abstract

Calibration devices for the Forward Scattering Spectrometer Probe (FSSP) and the Optical Array Probe (OAP) were developed. The device used with the FSSP is a rotating pinhole calibrator. It utilizes light diffracted by a pinhole of a diameter to simulate scattered light from a water droplet. This device can be used to calibrate the FSSP, measure the FSSP's optical collection angles and for instrument alignment and troubleshooting. The device used with the OAP is a rotating reticle calibrator. Chrome disks of a known diameter on the reticle are used for calibration of the OAP and for determining the OAP's response to our-of-focus particles in the probe volume.