CG-4DLSS MISSED LIGHTNING DETECTIONS DUE TO STRONG STROKES

摘要

The Cloud to Ground component of the Four Dimensional Lightning Surveillance System (CG-4DLSS) is a network of six sensors that detect cloud to ground lightning strokes in and around Cape Canaveral Air Force Station (CCAFS) and NASA Kennedy Space Center (KSC). One of the main purposes of the CG-4DLSS is to help the space launch programs evaluate the likelihood of lightning induced current damage to electronics in satellite payloads, space launch vehicle avionics, test equipment, and other key facilities. It has been reported that CG-4DLSS sometimes fails to detect strong lightning strokes, which caused great concern. An estimate was previously made for the missed detection rate for lightning with peak currents larger than 50 kA. However, the missed detection rate for all lightning stroke peak current values was not available. This paper provides the framework to expand the misdetection rate estimate. In an attempt to provide an analysis framework at estimating the misdetection rate of the CG-4DLSS for lightning strokes of all peak currents, we have constructed a statistic model based on the logistic probability function. In lieu of any information on how the detection rate varies with peak current, we assumed a logistic curve would be an adequate approximation across all peak currents. The previous study that showed 28% of strokes I_p ≥ 50 kA are missed by CG-4DLSS was used to tune the logistic curve. We combined that with the known frequency distribution of lightning peak current to estimate the total missed detections of CG-4DLSS. We found that the missed detection rate due to strokes I_p ≥ 50 kA (named the Specific Misdetection Rate in this paper) is slightly below 5%. This is fairly close to the subjective anecdotal estimate of 4% or more by experienced users of CG-4DLSS data.