Satellite Cloud Data Analytics in Support of the Lunar Laser Communications Demonstration

Clouds are atmospheric phenomena that are organized on scales from a single kilometer to thousands of kilometers. Because they are composed of water droplets and/or ice crystals they pose a serious attenuation problem for space to earth communications at optical frequencies (1550 nm). Atmospheric fades exceeding several decibels (dB) are frequent even for cirrus clouds. Therefore, the mitigation of clouds is a key driver in the performance of free space to ground optical communication (FSOC) systems. One mitigation technique is to identify geographically diverse ground sites that are uncorrelated from a climatological perspective. This increases the probability that at a given time a Cloud Free Line of Sight exists. Multispectral imagery from the Meteosat Second Generation (MSG) and GOES is used to develop a high resolution, multi-year cloud climatology. The cloud algorithm generates a clear sky background for each pixel in the scene at both visible and infrared wave bands and uses threshold techniques to determine the probability of cloud. The algorithm is run on imagery at 15 minute and 4km resolution for the period 1995 – 2012. The Lasercom Network Optimization Tool is used to identify the optimal sites that together produce high system availability. To facilitate the handling of which site is most optimal in an operational setting, a satellite based cloud forecasting algorithm is applied to sequences of cloud scenes to produce short term predictions of their positions. Applications of this technology were recently used to support NASA's Lunar Laser Communications Demonstration. Results from this demonstration will be shown at the conference.