Using FORTE Data as a Proxy for Upcoming Simultaneous Optical and Radio Frequency Measurements of Lightning Flashes from Geosynchronous Orbit

In early-to-mid 2019, the Space and Endo-atmospheric Nuclear detonation detection

Surveillance Experimentation and Risk-reduction (SENSER) payload on the STPSat-6 will join the

two Geostationary Operational Environmental Satellite (GOES) R-series platforms in

geosynchronous orbit above the western hemisphere. The SENSER experimental payload is a

partnership between United States Department of Energy’s National Nuclear Security

Administration, Los Alamos National Laboratory, and Sandia National Laboratories, and includes

three experiments focusing on (1) optical, (2) hard radiation, and (3) radio frequency remote

sensing technologies.

The VHF sensing capabilities of the Radio Frequency Sensor (RFS) on the SENSER payload

provide a unique opportunity to examine coincident optical and RF lightning emissions from a

similar vantage point across a hemispheric domain that extends far beyond the reach of

regional Lightning Mapping Array (LMA) VHF systems. RFS will be able to measure lightning

over the open ocean, for example, where particularly energetic flashes are common. Data

fusion among the GOES16/17 Geostationary Lightning Mapper (GLM) lightning flash clusters,

GOES16/17 Advanced Baseline Imager (ABI) cloud features, and the SENSER RFS VHF sources

will make it possible to construct a multi-faceted view of lightning emissions and how they are

modified on their way to orbit by such processes as scattering in the cloud medium (optical),

and interactions with the ionosphere (RF).

We use coincident optical and VHF measurements collected by the Fast On-orbit Rapid

Recording of Transient Events (FORTE) satellite to demonstrate the value of future comparisons

between SENSER/RFS and GLM. The FORTE RF system (30-300 MHz coverage) is used as a proxy

for RFS data, and the FORTE Optical Lightning System (OLS) Lightning Locating System (LLS) is

used to emulate GLM observations. OLS/LLS was a CCD lightning imager based on the

NASA/MSFC design. It operated at 777.4 nm with a nominal frame rate of 400-500 FPS and an

approximate pixel spacing of 10 km at ground level. By comparison, GLM operates at 500 FPS

with a 9-14 km pixel resolution. We apply a coherency filter and lightning flash clustering

algorithm (LFCA) to 13 years of FORTE OLS/LLS measurements between 1997 and 2010 that are

based on the GLM algorithms. We then define FORTE RF system VHF features and integrate the

3-years of VHF waveform data (1997-2001) into the LFCA hierarchy as children of “flash”

features and step-siblings of “group” features. General statistics for all coincident features and

individual cases of unique flash types (i.e., laterally propagating flashes, optical-suggested

continuing currents, superbolts, etc.) are presented that compare the incidence and timing of

optical and RF signals in a large population of flashes.