Aerospace & Defense Technology - May 2021 - 25

Tech Briefs

resources, delay their reactions, or react incorrectly to tactical situations. This can ensure higher success rates for both air and ground
combat missions by confusing adversaries and causing them to expend resources, delay their reactions, or react incorrectly.
This work was done by Phyllis Nixon for the Air University Air and
Staff College. For more information, download the Technical Support Package (free white paper) at www.aerodefensetech.com/tsp
under the Unmanned Vehicles & Robotics category.

Calibrated Long-Wave
Infrared (LWIR) Thermal and
Polarimetric Imagery of
Small Unmanned Aerial
Vehicles (UAVs) and Birds
Producing a set of well-calibrated imagery, both
conventional LWIR thermal (watts/cm2-sr) and its
corresponding polarimetric imagery (percent
radiance polarized), helps evaluate the ability to
distinguish between small UAVs and birds of similar size and dimensions.
Army Research Laboratory, Adelphi, Maryland

C

urrently, agencies within the Department of Defense
(DOD) and the private sector are trying to develop techniques capable of detecting the presence of small unmanned
aerial vehicles (UAVs) at ranges on the order of 1-5 km. Often
complicating this effort is the presence of small birds of similar dimensions that are frequently mistaken to be small UAVs
when imaged using various methodologies, such as visible,
short-wave infrared (SWIR) and thermal imaging.
Initially, research was limited to long-wave infrared (LWIR)
thermal imaging that, in theory, should be effective for both dayand night-time operation. The goal was to record a preliminary set
of calibrated radiometric and polarimetric images in which both
small UAVs and birds were present in the scene. Targets (i.e., UAV
and/or birds) within each image were segmented and regions of
interest (ROI) were generated by tracing a circumference around
the object. Pixel values were then averaged to yield both a radiometric value (watts/cm2-sr) and a corresponding polarimetric
value (percentage linearly polarized) in order to quantify similarities and differences between " generic " bird and UAV signatures.
Although LWIR radiometric thermal signature capture and
analysis techniques are very mature and well understood,
thermal polarimetric methods and analysis are less developed.
For the polarimetric analysis presented here, the well-accepted
Stokes image methodology that effectively yields the percentage of the overall radiance emitted/reflected from the object
that is linearly polarized will be used.
The most common approach for measuring the polarization
state for emitted or reflected light is to measure the Stokes paFree Info at http://info.hotims.com/79413-760

Aerospace & Defense Technology, May 2021

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http://www.aerodefensetech.com/tsp http://info.hotims.com/79413-760 http://www.abpi.net/ntbpdfclicks/l.php?202105ADTNAV

Aerospace & Defense Technology - May 2021

Table of Contents for the Digital Edition of Aerospace & Defense Technology - May 2021

Aerospace & Defense Technology - May 2021 - Intro
Aerospace & Defense Technology - May 2021 - Sponsor
Aerospace & Defense Technology - May 2021 - Cov1
Aerospace & Defense Technology - May 2021 - Cov2
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Aerospace & Defense Technology - May 2021 - Cov3
Aerospace & Defense Technology - May 2021 - Cov4
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