Current and Future Processing Techniques for Orbital Optical Lightning Sensors

Abstract:

A comparative overview of the processing techniques used to detect lightning from space is presented. The Optical Transient Detector (OTD) was launched in 1995 and collected optical lightning data until the year 2000. The Lightning Imaging Sensor (LIS) was launched in 1997 as part of the Tropical Rainfall Measuring Mission (TRMM) and the LIS flight spare in 2017 to the International Space Station (ISS). The data from the two LIS instruments were processed using nearly the same code as OTD. When the first Geostationary Lightning Mapper (GLM) was launched in 2016, the data were processed using code derived from the OTD and LIS codes, but with notable modifications. The EUMETSAT Lightning Imager (LI), part of the Meteosat Third Generation (MTG) mission will also use code that is based on the OTD/LIS/GLM data processing concepts. All of these instruments use their own code bases, but their conceptual organizations are very similar. Each filters the raw input data to eliminate non-lightning pulses, each geolocates the remaining pulses, and then each clusters their data into higher level products. We will describe the common and unique filtering concepts used in the current processing of the OTD, TRMM-LIS, GLM, ISS-LIS, and LI instruments along with possible future enhancements to the filtering techniques. We will also discuss the clustering method used in the various optical lightning instruments including some possible higher level lightning products and clustering categories. Validation is critical in evaluating the data from these instruments. We will describe a technique to validate the orbital optical lightning data in areas where ground truth datasets are lacking. We will introduce the concept of an open source, common optical lightning processing code that can be used to process all of the instruments mentioned here plus any other future or past orbital-based lightning detectors.