Lightning Observations from Space (Invited Presentation)

The Optical Transient Detector (OTD) and the Lightning Imaging Sensor (LIS) were the first space-based lightning sensors to use two-dimensional focal planes to both detect and locate lightning activity.  Previously, space-based optical lightning instruments used single photo-diodes, which provided not only poor location information but very low detection efficiency (DE) because the reflected light from many clouds in the field of view would overwhelm all but the strongest lightning flashes.  OTD and LIS improved the lightning DE by over an order of magnitude and provided the first detailed maps of total lightning climatology on a global basis.  They provided twenty years of continuous lightning observations, showing essentially no change in flash rates over the observation period.  To this day, no large area coverage ground network has matched the total lightning detection capability of LIS.

Following just over a year’s hiatus from observations, both a new Lightning Imaging Sensor (LIS) and the Geostationary Lightning Mapper (GLM), are scheduled for launch in November.  They promise to provide unprecedented lightning data.

The GLM will provide the first opportunity for the continuous optical observations of lightning over the entire lifetime of storms and storm systems, thus providing entirely new capabilities for both the research and operational communities.  The GLM uses the same detection techniques first implemented in LIS except on a much larger scale.  It uses a fully digital real time event processor (RTEP) instead of a hybrid analog-digital RTEP as implemented in LIS.  In addition it utilizes 56 parallel RTEPs instead of the single processor in LIS.  The RTEPs provide on orbit lightning event detection converting the sensor from an imager to an event detector.   Further more sophisticated event processing is performed on the ground.  The signal processing and unique design features of the GLM will be described in detail.  Overall, the GLM will have slightly better radiometric throughput than the LIS and should have similar overall performance.    

This paper will describe the instrument design, expected overall performance and a few of the anticipated applications.