The GLM laser beacon. Credit: NASA
SLR, NOAA, GOES, GLM, beacon 

SLR Helps Geolocate Lightning

June 28, 2017

ESC is applying cutting-edge laser beam technology to test the Geostationary Lightning Mapper (GLM) instrument, which locates lightning flashes day and night over the Americas and surrounding oceans. The NEN’s Satellite Laser Ranging (SLR) ground network helps GLM verify how well it tracks lightning in the night sky.

GLM is a National Oceanic and Atmospheric Administration (NOAA) instrument aboard NOAA’s GOES-16 satellite, which is undergoing post-launch testing. GLM images the Earth 500 times a second to detect transient light pulses at cloud tops produced by lightning channels within the cloud. When compared to regions of contrast, like coastlines, the images are used to determine applicable navigation corrections to accurately locate lightning on Earth.

But coastlines and other contrast markers are not visible at night, so SLR is testing NOAA-funded laser beacons at its ground station in Greenbelt, Maryland. When switched on for testing, the laser points directly at GOES-16, creating pulses of laser light to illuminate GLM with simulated lightning-like transients, which GLM interprets as lightning emanating from Greenbelt. So the SLR beacon functions in a similar manner as visible coastlines by providing a known location to validate the image navigation.

The laser beacon’s initial study purpose is twofold: It investigates the concept that lasers could help navigate GLM images and also evaluates how the GLM instrument behaves during day and night. In this way, the beacon helps to validate analytical models of the predicted instrument navigation and could provide unique insight into whether the camera shifts throughout its daily cycle due to thermal or other forces.

Over the coming weeks, SLR plans to test the laser beacon concurrently with a second laser beacon, which will be installed at the SLR ground station in California. (Multiple points of reference should improve image navigation.)

By tracking lightning, GLM will contribute to critical weather forecasting and help inform the public about violent storms.