Laboratory calibration of the optical transient detector and the lightningimaging sensor

The authors present in detail the laboratory apparatus and techniques that were used to complete a full radiometric calibration of two space-based lig htning detectors: the optical transient detector (OTD) and the lightning im aging sensor (LIS) that were developed at the National Aeronautics and Spac e Administration Marshall Space Flight Center These instruments are nadir-s taring imagers that are optimized to detect and locate lightning from low E arth orbit during day and night conditions. The radiometric calibration con sisted of characterizing the pixel response to steady and transient optical sources, sensor field of view, and sensor spectral response. The transient optical signals produced in the calibration laboratory were used to derive estimates of sensor lightning detection efficiency.