Coordinated observations of optical lightning from space using the FORTE photodiode detector and CCD imager

This paper presents an overview of the coordinated observation of optical l ightning from space using the photodiode detector (PDD) and CCD-based image r known as the Lightning Location System (LLS) aboard the Fast On-Orbit Rec ording of Transient Events (FORTE) satellite. PDD/LLS coincidence statistic s are presented and show that both the detected energy density and the dete cted peak irradiance of optical lightning events are proportional to the nu mber of LLS pixels (pixel multiplicity) which are activated during the even t. The inference is that LLS pixel multiplicity is more a function of the d etected intensity and horizontal extent of the optical event rather than a direct indicator of the degree of scattering. PDD/LLS event coincidence is also used to improve upon traditional recurrence/clustering algorithms that discriminate against false LLS events due to energetic particles and glint . Energy density measurements of coincident events show that about 4% of th e optical energy detected by the broadband PDD appears in the narrowband LL S. This is in general agreement with ground-based measurements and with ass umptions incorporated into the design of current and planned CCD-imaging se nsors.