Group Data and Detection Efficiency Analysis for the Modular Multispectral Imaging Array and the Lightning Imaging Sensor

Abstract
The Modular Multispectral Imaging Array (MMIA), part of the Atmosphere‐Space Interactions Monitor (ASIM), provides high spatial and temporal resolution measurements of the optical emission from lightning and transient luminous events in three bands. Lightning is known to radiate in two of these bands: 337 and 777 nm. To help facilitate analysis of emission characteristics, an algorithm to produce group‐level products from MMIA data using both spectral bands is developed. The groups are formed by identifying clusters of pixels in a single video frame that exceed a particular threshold, similar to what is done with other space‐based lightning instrument data. The groups are analyzed along side data from the International Space Station Lightning Imaging Sensor (ISS LIS). When MMIA detects a group with 337 nm emission, ISS LIS also detects it 80.6% of the time; 89.6% of MMIA groups with 777 nm emission are also detected by ISS LIS. Overall, the detection efficiency of ISS LIS increases for groups with larger area and groups that are brighter. Conversely, 96% of ISS LIS groups occur with MMIA groups with both 337 and 777 nm emission. The 337 nm MMIA groups span larger areas than the 777 nm groups that occur simultaneously, and the MMIA 777 nm groups tend to be smaller than the ISS LIS groups. Finally, two examples of how the grouping algorithm can be used to study the physics of lightning are presented.