Transcript Document

Optronic Measurement, Testing and the
Need for Valid Results Example of
Infrared Measurements for Defence
Countermeasures
Azwitamisi E Mudau, C.J. Willers, M.J. Hlakola,
F.P.J. le Roux, B. Theron, J.J. Calitz, M.J.U. Du Plooy
Defense, Peace, Safety and Security, Council for Scientific and
Industrial Research
[email protected]
Overview
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Peace and Humanitarian Support
Heat Seeking Missiles and Infrared Countermeasures
Infrared Measurements at the Optronic Sensor Systems
Airborne Infrared Countermeasure Characterization
Strategy for Successful Measurement
Details of Experiments
 Equipment used and Settings
 Experimental layout
 Understanding Infrared Temperature Measurements
 Results
 Reference Measurements
 Flare Measurements
 Conclusion
© CSIR 2010
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Peace and Humanitarian Support
• South African Air Force transport
aircraft are the platforms of choice to
deliver humanitarian aid
• are used in rescue and support
missions
• used to carry soldiers into countries
for UN sanctioned peace support and
stabilization efforts
• the core of the SANDF’s transport
and lift capabilities acquired by the
country at tremendous cost.
• If they are destroyed or attacked it
seriously limits the ability for South
Africa to perform the humanitarian
role
Heat Seeking Missiles
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Infrared Countermeasures
• Airborne IRCM flares are defensive mechanisms employed from
military and civilian aircraft to avoid detection and attack by enemy
infrared seeker missiles.
The Infrared Signature of the Aircraft
 The engine hot parts
 Exhaust plume
 The skin of the airframe
Infrared Measurements at the Optronic
Sensor Systems
Airborne Infrared Countermeasure
Characterization
•
To model airborne IRCM
flares effectively and correctly
as missile countermeasures
- Radiant intensity
- Emissivity
- Temperature
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Strategy for Successful Measurement
Sensors
Understand the sensor
Characteristics & Procedures
Strategy is required for
measuring the
signatures of infrared
countermeasure flares
Details of Experiment
 Measurements were performed
using Cedip Jade LWIR thermal
imager
 Fluke 574 Precision Infrared
Thermometer

A high temperature Electro Optics
Industries extended-area
blackbody
(b) MWIR Imager Responsivity
(c) SWIR Imager Responsivity
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Normalized Response
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Normalized Response
Normalized Response
(a) LWIR Imager Responsivity
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Wavelength (microns)
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Wavelength (microns)
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Wavelength [micros]
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Prior Infrared Measurements
 The Jade IR thermal imagers need to
be CALIBRATED
 The objective of the calibration is to
obtain a relationship between the
incident flux and the instrument output
(digital level).
 They are calibrated over a broad
range of temperatures.
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During Infrared measurement trials
Flare
Launcher
Reference
Measurements
Blackboy
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420
m
Capture quality IR images of
the unit under test (UUT) and
two reference source
(blackbody)
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Instrument settings and
meteorological data
Weather
Station
Infrared Mobile
Laboratory
Atmospheric Transmittance
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To account for the target
radiation losses through the
atmosphere
MODerate spectral resolution
atmospheric TRANsmission
(MODTRAN) code
Atmospheric conditions during test
Parameter
2009/11/11
2009/11/12
Atmospheric Temperature [°C]
20.7-28
25.3-29.4
Humidity [%RH]
51-77
35-58
Cloud Cover
Partially Cloudy
Cloudy
Visibility [km]
Good
Good
Understanding Infrared Temperature
Measurements
 “The same as” measurement technique was used to calculate the
Pyrolysis flame temperature (Tm).
  L T  S
c bb
c
ac
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d     m Lbb Tm  S am d    1   m Lbb Ta  S ae d   Lpath
Tc is determined from the calibration curves
by Tc = fcal(D), where D is the measured digital
level and fcal is the calibration curve
ae is the spectral atmospheric transmittance
between the measured source and ambient
environment (near unity ) and Lpath is the
c is the calibration source emissivity
atmospheric path radiance (near zero) .
 Lbb(T) is blackbody radiation of a source with
temperature T
 am is the spectral atmospheric transmittance
between the instrument and the object during
S is the instrument spectral response
 ac is the atmospheric transmittance during
calibration
Ta is the ambient environment temperature
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measurement
 m is the measured source emissivity
 Tm is the unit under test temperature
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Reference Measurements
(a) Blackbody Reference in the MWIR Spectral Band
(b) Blackbody Reference in the SWIR Spectral Band
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Blackbody Reference # 112
Blackbody Reference # 212
Blackbody Reference # 211
Blackbody Reference # 112
Blackbody Reference # 211
Blackbody Reference # 212
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Temperature [K]
Temperature [K]
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Test Point
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Time [s]
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MWIR (K)
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Fluke (K)
SWIR (K)
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Time [s]
0.8
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Percentage Difference (%)
MWIR MWIR
/ SWIR / Fluke
SWIR /
Fluke
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709.76 ± 2.13
709.34 ± 2.84
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0.20
0.25
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707.54 ± 3.14
718.98 ± 1.76
708.50
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0.14
1.47
212
704.04 ± 5.97
709.36 ± 2.64
712.15
0.75
1.15
0.39
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Temperature vs Test Point
720
Fluke
SWIR
MWIR
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Temperature [K]
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712
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704
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Test Point
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Test Point
MWIR (K)
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Fluke (K)
SWIR (K)
Percentage Difference (%)
MWIR MWIR
/ SWIR / Fluke
SWIR /
Fluke
211
709.76 ± 2.13
709.34 ± 2.84
711.15
0.06
0.20
0.25
112
707.54 ± 3.14
718.98 ± 1.76
708.50
1.60
0.14
1.47
212
704.04 ± 5.97
709.36 ± 2.64
712.15
0.75
1.15
0.39
Flare Measurements
(a) Normalized Intensity at MWIR Spectral Band as a
Function Burning Time
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Normalized Burning Time
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(b) Normalized Intensity at SWIR Spectral Band as a
Function Burning Time
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Normalized Intensity
Normalized Intensity
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(a) Flare Temperature in MWIR Spectral Band
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Normalized Burning Time
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(b) Flare Temperature in SWIR Spectral Band
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Temperature [K]
Temperature [K]
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0
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Normalized Burning Time
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1800
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Normalized Burning Time
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Conclusion
 The methodology used was developed over several field trials,
spanning several years.
 The deep understanding of the instruments is essential in exploiting
the instrument and avoiding its weaknesses.
 reference measurements are essential, during field trial to ensure
confidence in the measured data.
 The results show that atmospheric corrections were done accurately
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Thank you