LIS
type: Concept
change note: 2020-01-29 17:24:49.0 [sritz] update Definition (LIS is designed to investigate the global incidence of lightning, its correlation with convective rainfall, and its relationship with the global electric circuit. Conceptually, LIS is a simple device, consisting of a staring imager optimized to locate both intra cloud and cloud-to-ground lightning with storm-scale resolution over a large region of surface on Earth, to mark the time of occurrence, and to measure the radiant energy. It will monitor individual storms within the field of view (FOV) for 80 seconds, long enough to estimate the lightning flash rate. Location of lightning flashes is determined to within 5 km over a 600-km × 600-km FOV. The LIS design uses an expanded optics wide-FOV lens, combined with a narrow-band interference filter that focuses the image on a small, high-speed, charge-coupled-device focal plane. The signal is read out from the focal plane into a real-time data processor for event detection and data compression. The particular characteristics of the sensor design result from the requirement to detect weak lightning signals during the day when the background illumination, produced by sunlight reflecting from the tops of clouds, is much brighter than the illumination produced by the lightning. A combination of four methods is used to take advantage of the significant differences in the temporal, spatial, and spectral characteristics between the lightning signal and the background noise. First, spatial filtering is used to match the instantaneous FOV of each detector element in the LIS focal-plane array to the typical cloud-top area illuminated by a lightning event (about 5 km). Second, spectral filtering is applied, using a narrow-band interference filter centered about the strong hypoiodite ion (OI) emission multiplet in the lightning spectrum at 777.4 nm. Third, temporal filtering is applied. The lightning pulse duration is of the order of 400 microseconds, whereas the background illuminat…
change note: 2020-01-29 17:40:54.0 [sritz] update Definition (https://pmm.nasa.gov/TRMM/LIS);
definition: LIS is designed to investigate the global incidence of lightning, its correlation with convective rainfall, and its relationship with the global electric circuit. Conceptually, LIS is a simple device, consisting of a staring imager optimized to locate both intra cloud and cloud-to-ground lightning with storm-scale resolution over a large region of surface on Earth, to mark the time of occurrence, and to measure the radiant energy. It will monitor individual storms within the field of view (FOV) for 80 seconds, long enough to estimate the lightning flash rate. Location of lightning flashes is determined to within 5 km over a 600-km × 600-km FOV. The LIS design uses an expanded optics wide-FOV lens, combined with a narrow-band interference filter that focuses the image on a small, high-speed, charge-coupled-device focal plane. The signal is read out from the focal plane into a real-time data processor for event detection and data compression. The particular characteristics of the sensor design result from the requirement to detect weak lightning signals during the day when the background illumination, produced by sunlight reflecting from the tops of clouds, is much brighter than the illumination produced by the lightning. A combination of four methods is used to take advantage of the significant differences in the temporal, spatial, and spectral characteristics between the lightning signal and the background noise. First, spatial filtering is used to match the instantaneous FOV of each detector element in the LIS focal-plane array to the typical cloud-top area illuminated by a lightning event (about 5 km). Second, spectral filtering is applied, using a narrow-band interference filter centered about the strong hypoiodite ion (OI) emission multiplet in the lightning spectrum at 777.4 nm. Third, temporal filtering is applied. The lightning pulse duration is of the order of 400 microseconds, whereas the background illumination tends to be constant on a time scale of secon…
in scheme: instruments

Imaging Spectrometers/Radiometers
type: Concept