The New Mesoscale Eastern Range Lightning Information Network

This presentation will provide an overview of the new Mesoscale Eastern Range Lightning Information Network (MERLIN) being installed for use by Cape Canaveral Air Force Station and NASA Kennedy Space Center.  The current primary lightning detection system is the Four Dimensional Lightning Surveillance System (4DLSS) is becoming unsustainable since the sensors it uses are no longer being manufactured.  Therefore, a replacement lightning detection system is needed.  In addition, several performance upgrades will be provided by MERLIN.

MERLIN consists of ten Total Lightning Sensor Model 200 sensors made by Vaisala that detect both cloud-to-ground lightning and lightning aloft.  This compares to the current 4DLSS that has six out-of-date cloud-to-ground lightning sensors and nine out-of-date lighting aloft sensors.  MERLIN uses Vaisala’s new Total Lightning Processor, while 4DLSS uses the older CP-8000 processor. 

For cloud to ground lightning, MERLIN detects and locates individual return strokes using magnetic direction finding and time of arrival, as does 4DLSS.  However, the new processor has digital signal processing that provides several advantages.  First, the timing precision is significantly improved so that time of arrival locations are now about as accurate as direction finding solutions for nearby return strokes.  In addition, the digital signal processing allows better waveform analysis that will increase detection efficiency for cloud-to-ground lightning strikes to tall structures and for strong strokes.  Another improvement of MERLIN is the real-time integration of ten in-range NLDN sensors in Florida, South Carolina, and the Bahama Islands.  This provides longer range and more robust performance of cloud-to-ground lightning than 4DLSS and makes MERLIN a hybrid local/regional detection system for cloud-to-ground lightning. 

For lightning aloft, MERLIN uses VHF interferometry rather than the time of arrival of 4DLSS.  Due to a longer integration time of the interferometers, MERLIN detects larger subcomponents of the lightning aloft flash such as recoil streamers with typical lengths of about 1 km.  The 4DLSS tends to detect smaller parts of the lightning aloft flash such as stepped leaders with typical lengths of about 0.1 km.  One shortfall of MERLIN compared to 4DLSS is the loss of detecting height for lightning aloft.  While lightning aloft is located, the location solution provides only the x-y projection of the event on the ground.

Initial testing of MERLIN indicates excellent performance for cloud-to ground lightning.  Preliminary results indicate median location accuracy within the network of about 60 m, which is almost 4.5 times better than 4DLSS’s CG stroke location accuracy of about 260 m.  The cloud-to-ground detection flash detection efficiency of MERLIN is about 98%.  Testing the lightning aloft performance of MERLIN versus 4DLSS is difficult since they detect very different parts of the lightning aloft.  However, comparison of MERLIN and 4DLSS indicates that MERLIN’s lightning aloft detection efficiency and location accuracy is as good, if not better than 4DLSS within 30 nmi of the networks center.

Mention of any commercial product or vendor does not represent any government endorsement.