Wide angle infrared cloud imaging for measuring cloud statistics in support of earth space optical communication

Abstract

ABSTRACT Previous research at Montana State University led to the de velopment of the Infrared Cloud Imager (ICI) for measuring downwelling cloud and sky thermal emission for producing cloud coverage statistics using radiometrically calibrated images of the sky. This technique, that was developed primarily for detection of clouds for studies of arctic climate, provides benefits over commonly used systems by producing localized high resolution data in comparison to satellites images, and, in contrast to visible systems, provides continuous day and night operation. As a continuation of the first effort, in collaboration with the Optical Communications Group at the NASA’s Jet Propulsion Laboratory (JPL), here we present a new generation of the ICI that can be used to monitor the cloud coverage of a site that can house a ground telescope dedicated to Earth-space optical communication paths. This new instrument, based around the FLIR Photon camera, expands the field of view (FOV) from 20° to 50° (up to 100° in the latest version), reduces instrument size, reduces instrument cost, and extends the time between calibrations to hours instead of minutes. This has been accomplished by characterizing the changes in the output data for changes in the camera’s internal temperature while viewing a constant source. Deployment of this instrument has taken place at JPL’s Table Mountain facility, CA, and Bozeman, MT. Keywords: Optical Communication, Thermal Imaging, Cloud Cover Statistics, Infrared Cloud Imaging