3.2 Integration of Broadband Interferometry into Lightning Mapping Arrays

Tuesday, 24 January 2017: 8:45 AM
Conference Center: Tahoma 1 (Washington State Convention Center )
Mark A. Stanley, New Mexico Tech, Socorro, NM; and W. Rison, P. R. Krehbiel, J. N. Tilles, N. Liu, L. Boggs, R. G. Brown, J. G. Wilson, and M. Stock

A broadband interferometer (INTF) samples raw VHF data at 3 or more
antennas in order to produce highly detailed 2-D azimuth/elevation
maps of lightning progression with fine time resolution.  In contrast,
a Lightning Mapping Array (LMA) uses the time-of-arrival technique to
obtain a detailed 3-D map of lightning progression, but with at least
an order of magnitude lower time resolution.  Consequently, LMAs are
less effective at mapping the progression of faster events such as
K-changes and dart leaders.  In addition, an LMA can have difficulty
mapping leaders to ground due to effects such as near simultaneous
stepping along branches as well as VHF attenuation to more distant LMA

A technique has been developed to time align raw INTF VHF data to
within a few nanoseconds of the LMA expected arrival times even
without sampling a GPS output directly with the INTF.  This capability
has led to a new mode of hybrid INTF-LMA 3-D mapping in which the INTF
can provide precise event times like individual LMA stations, but with
the added information of azimuth and elevation to the source.  By
combining this information with the event times from two or more of
the closer LMA stations within an LMA network, we will show that a
more detailed 3-D image can be obtained than by just the LMA stations
alone.  We will also discuss how the use of extended baselines such as
the 100 meter ones in use during the 2016 campaign at the Kennedy
Space Center has extended the useful range of the interferometer.  In
addition, we will show how a large database of well over a million
VHF-LMA pairs has been used to characterize the gain pattern of the
INTF VHF antennas as well as investigate the relative sensitivity of
the INTF to the LMA as a function of range.  Finally, we will discuss
the application of interferometric imaging to locate and characterize
potentially simultaneous sources as opposed to present techniques
which only map the brightest ones within each time window.

- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner