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© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Course Overview

0. Intro, Administrative, and Course Overview1. Electromagnetic Spectrum & Infrared Fundamentals2. The Infrared Threat3. Missile Warning Receivers4. Aircraft Signatures5. Infrared Missile System Principles6. DIRCM Systems

– Increasing J/S Requirement– Legacy DIRCM (Broadband and Flash Lamp) Systems– Laser Jam (Closed Loop) DIRCM Systems

7. Test and Evaluation of DIRCM Systems

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

End of Module 0

QUESTIONS?QUESTIONS?

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Next Up

1. Electromagnetic Spectrum & Infrared Fundamentals

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

The Electromagnetic Spectrum & IR Fundamentals

Module 1

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Course Overview

1. Electromagnetic Spectrum & Infrared Fundamentals2. The Infrared Threat3. Missile Warning Receivers4. Aircraft Signatures5. Infrared Missile System Principles6. DIRCM Systems

– Increasing J/S Requirement– Legacy DIRCM (Broadband and Flash Lamp) Systems– Laser Jam (Closed Loop) DIRCM Systems

7. Test and Evaluation of DIRCM Systems

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Module 1 Overview

• Electromagnetic (EM) Wave Basics• Properties of EM Waves and Light• Regions of Interest in the EM Spectrum• Infrared Basics• Blackbody Radiation Physics and Terminology

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Propagation of Light as EM Waves

• ALL Electromagnetic radiation consists of an electric (E) field and a magnetic (H) field• The wave propagates at the speed of light, at right angles to the E/H field planes• If you cross the E Field vector with the H Field vector, you get the direction of travel of the EM

wave (known as the right hand rule)

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

• Light, like all electromagnetic waves, travels at the same fixed velocity (in a vacuum) 186,000 miles/second = 3 X 108 meters/second

• C = the speed light = 3 X 108 meters/second

• C = f or you can always remember the 2 Greeks >> C =C =

The Speed of Light

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

EM Wave Terminology

• The amplitude is related to the intensity of the light in Volts/Meter.

• The period (T) is the time between crests of the wave in seconds.

• The wavelength ( ) is the physical distance between wave crests

• The frequency (or f ) is the inverse of the period, and vice-versa.

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Direction of E field determines the polarization of an EM wave.

With E field in vertical direction wave is said to be vertically polarized

Direction of travel by the right hand rule crossing the E vector into the H vector

E

HHorizontal Circular

EE

Polarization

Can be right or left Can be right or left hand circularly hand circularly polarizedpolarized

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

EM Wave Polarization Video

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Diffraction

• When light passes through a narrow opening, it tends to spread out as if the opening itself were a very small point source of light

•The bending of light when it passes through a narrow opening or along the edge of a barrier is known as diffraction

Note: Diffraction limits the resolution of an optical system

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

The Electromagnetic Spectrum

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Optical Band of the Electromagnetic Spectrum

Optical frequencies, or light can be both visible and invisible to the unaided eyeNote: Boundaries, UV, & IR Band Nomenclature are somewhat arbitrary and are author/text dependent

ROYGBV

RedRed,, orangeorange,, yellowyellow, , greengreen, , blueblue, , violetviolet

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

NVG(0.65-0.95)

FLIR3-5, 8-12

X-Band Radar10 GHz, 3 cm

CCD TV0.55-0.95

Older IR MissilesNear IR

ModernIR MissileThreat3-5

UV MWS0.1-0.4

EO Wavelengths shown in microns (EO Wavelengths shown in microns (m)m)

Electromagnetic Spectrum Charts (cont.)

This is the IR Threat

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Diffraction Limited Resolution

1.22 D

~R

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Phase Angle Properties

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Interference Properties of Light

• When two or more light waves meet at the same place and time, their amplitudes will add by the principle of superposition

• If crests meet crests they add together to produce a larger amplitude and this is constructive interference

• If crests meet with troughs they add together to produce a smaller amplitude and this in know as destructive interference

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

The Interaction of Light With Matter

Medium 1 Medium 2

When light (EM energy) strikes the boundary of some type of matter, three things can happen:

3

Boundary between two different media such as air/glass or air/water

2. REFRACTION - Radiation is passed or transmitted into the second media (also called transmission). If the index of refraction is different between the two medium, the light will be bent or refracted () according to Snell’s Law

1. REFLECTION - Radiation is turned back into the first medium ()

3. ABSORPTION - Process in which the energy of the incident photons are absorbed and changed into molecular energy & heat ( )

Note: The sum of these three coefficients ( must = 1

21

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

On 11 February 1800, Sir William Herschel was On 11 February 1800, Sir William Herschel was testing filters for viewing the sun so he could observe testing filters for viewing the sun so he could observe sun spotssun spots

When using a red filter he found there was a lot of When using a red filter he found there was a lot of heat producedheat produced

Herschel discovered infrared radiation by passing Herschel discovered infrared radiation by passing sunlight through a prism and holding a thermometer sunlight through a prism and holding a thermometer just beyond the red end of the visible spectrumjust beyond the red end of the visible spectrum

This thermometer was meant to be a control to This thermometer was meant to be a control to measure the ambient air temperature in the roommeasure the ambient air temperature in the room

He was shocked when it showed a higher He was shocked when it showed a higher temperature than the visible spectrumtemperature than the visible spectrum

Further experimentation led to Herschel's conclusion Further experimentation led to Herschel's conclusion that there must be an invisible form of light beyond that there must be an invisible form of light beyond the visible spectrum.the visible spectrum.

The Discovery of Infrared

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

IRIR

~0.7~0.7--1000 microns1000 microns

When we speak of infrared, we mean that portion of the electromagnetic spectrum that lies between visible light on one side and microwaves on the other. Quantitatively, is is expressed as the region extending from a wavelength of ~ 0.7 microns to ~1000 microns

The Infrared Spectrum

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

• A source at the origin radiates optical power such that P0 is radiated into a cone as shown

• Other powers may be radiated in other directions.

• For the first cone, the power per unit area at a distance R1 away is…

P0/A1

and is called the “Irradiance”

• The Irradiance at distance R2 is

P0/A2

• Since the illuminated area increases as the square of R, i.e. A2/A1=(R2/R1)2, in a non-absorbing medium the Irradiance produced by the source varies as inverse R-squared.

Radiometry

AA22

PP00AA11

RR22

RR11

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

AA22

PP00AA11

RR22

RR11

• Irradiance is given the symbol “E”and is expressed in the units W/cm2.

• Missiles care about the quantity “Irradiance” because the power they receive Pr is determined by that value and by the missiles’s collection area Am. That is…

Pr2=E2 x Am =(P0/A2) x Am

is the power the missile receives when it is at the range R2

• Since the Irradiance increases as the inverse-square of R, the missile receives greater and greater power as it flies toward the source.

Radiometry (cont.)

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

•• The angular region contained in the The angular region contained in the cone is called the cone is called the ““solid anglesolid angle”” of the of the cone, cone, and is given by and is given by

=A/R=A/R22..

•• This definition is true for any arbitrary This definition is true for any arbitrary angular region which can differ from angular region which can differ from that of a cone.that of a cone.

•• Since the illuminated area varies as RSince the illuminated area varies as R--squared, the solid angle of the squared, the solid angle of the illuminated region does not change illuminated region does not change with range.with range.

•• A radiometric quantity called A radiometric quantity called ““Radiant IntensityRadiant Intensity”” has been defined and is has been defined and is calculated using the expression calculated using the expression P/P/.. .. Since the power Since the power PP00 uniformly fills uniformly fills the solid angle region, in a nonthe solid angle region, in a non--absorbing medium, the Radiant Intensity absorbing medium, the Radiant Intensity does not varydoes not vary with range.with range.

Radiometry (cont.)

AA22

P0AA11

RR22

RR11

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

•• Radiant intensity is given the Radiant intensity is given the symbol symbol ““II”” and is expressed in the and is expressed in the units units W/srW/sr..

•• IRCM engineers care about the IRCM engineers care about the quantity quantity ““Radiant IntensityRadiant Intensity””because that value describes the because that value describes the strength of target and jammer strength of target and jammer sources without specifying range *sources without specifying range *

•• Irradiance can be found from Irradiance can be found from Radiant Intensity by dividing by Radiant Intensity by dividing by the rangethe range--squared. That issquared. That is……

EE22=I/(R=I/(R22))22

Is the Irradiance produced at a Is the Irradiance produced at a range range RR22 by a source of Radiant by a source of Radiant Intensity Intensity ““II””..

** This is true for a nonThis is true for a non--absorbing medium.absorbing medium.

Radiometry (cont.)

AA22

P0AA11

R2

R1

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

• Aircraft targets and jamming transmitters are optical sources whose radiation strengths may be expressed in terms of Radiant Intensity or Irradiance.

• Whatever radiometric quantity is used, IRCM engineers refer to the aircraft radiation strength as “S” for signature, and to the Jammer strength as “J”. The IRCM system’s J/S is then determined as the ratio.

• Since aircraft and jamming systems can radiate different amounts in different directions, the apparent values of S, of J, and of J/S, can vary with the observer’s viewing perspective.

• As an example, a fixed-wing aircraft signature may be 1000 W/sr at a tail perspective where aircraft engines are unobscured, but may be only 100 W/sr when viewed nose-on.

• Since the atmosphere will typically remove power from any radiating cone through absorption, values of J and S may change with rangebeyond the standard R-squared multiplier.

Radiometry (cont.)

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

RADIOMETRIC UNITS

• The watt is the fundamental unit of optical power and measurement, and is defined as a rate of energy of one joule per second

• It is a function of both the number of photons and the wavelength of the photons

• Each photon carries an energy = h = hc/where h = Planck’s constant = 6.623 x 10 -34 Joule-sec

c = speed of light = 3 x 10 8 meters / sec wavelength of the photons

Watts

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Radiator Response Curves

Emissivity () = 1 (black body at 300°

0 10 20 30 (m)

= varies as wavelength(Selective Radiator)

= 0.9 (gray body)

Mon

ochr

omat

icEn

ergy

Den

sity

(Wat

t/cm

3-m

icro

n)

Need to specify the for the spectral band of interest• Usually specified as an average over a given spectral band• For example: = 0.3avg at 8-12 microns

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Important Laws of Radiation

•• Inverse Square Law Inverse Square Law

•• LambertLambert’’ s Cosine Laws Cosine Law

•• StefanStefan--BoltzmanBoltzman’’s Laws Law

•• WienWien’’s Laws Law

•• PlanckPlanck’’s Laws Law

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Defines the relationship between the irradiance (illuminance) frDefines the relationship between the irradiance (illuminance) from om a point source and the distance to ita point source and the distance to it

Inverse Square LawInverse Square Law

The intensity per unit The intensity per unit area varies in inverse area varies in inverse proportion to the square proportion to the square of the distance of the distance ---- why?why?

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Inverse Square Law & Divergence

Inverse Square Law

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

W T4

FOR A BLACKBODY = 1.0

T = Temperature (absolute)

= Emissivity

= Stefan Boltzman’s Constant5.670 x 10-8 W

cm2 k4

Note that if T is doubled, the Note that if T is doubled, the radiated emittance is radiated emittance is increased sixteen timesincreased sixteen times

Stefan-Boltzman’s Law (Thermal Radiation Law)

The amount of radiation emitted by a body is proportional to the emissivity and to the fourthpower of the absolute temperature of the body

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Wien’s Displacement Law

8 12

The wavelength at which the maximum radiance occurs is inversely proportional to the absolute temperature of the body (Kelvin):

max 2900/T microns

300300

9.69.6mm

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Planck’s Law

• In physics, Planck's law describes the spectral radiance of electromagnetic radiation at all wavelengths from a black body at temperature T. As a function of frequency ν, Planck's law is written as:

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Planck’s Law

RocketRocketExhaustExhaust

SolarSolar

Jet EngineJet EngineExhaustExhaust

EarthEarth(terrain)(terrain)

All bodies emit radiation at all wavelengths as

a function of the bodies absolute temperature

Weins Law

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

LambertLambert’’s (Cosine) Laws (Cosine) Law•• The irradiance or the The irradiance or the illuminance falling on any illuminance falling on any surface varies as the cosine surface varies as the cosine of the incident angleof the incident angle

•• Maximum at 90 degrees toMaximum at 90 degrees tothe surface (shown as 0 the surface (shown as 0 degrees here)degrees here)

The perceived measurement The perceived measurement area orthogonal to the incident area orthogonal to the incident flux is reduced at oblique flux is reduced at oblique angles causing the light to angles causing the light to spread out over a wider area spread out over a wider area than it would if perpendicular than it would if perpendicular to the measurement planeto the measurement plane

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

IRCM Terminology

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

• IR spectrum• Band pass• Radiant intensity• Watts per steradian• Watts per cm2

• IR signature

• Open loop IRCM• Closed loop IRCM• Optical break lock• Guidance suppression• J/S ratio

Common IRCM Terms

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Questions?

Module 1

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Next Up1. Electromagnetic Spectrum & Infrared Fundamentals2. The Infrared Threat3. Missile Warning Receivers4. Aircraft Signatures5. Infrared Missile System Principles6. DIRCM Systems

– Increasing J/S Requirement– Legacy DIRCM (Broadband and Flash Lamp) Systems– Laser Jam (Closed Loop) DIRCM Systems

7. Test and Evaluation of DIRCM Systems

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Module 5

Infrared Missile Systems

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Course Overview

0. Intro, Administrative, and Course Overview1. Electromagnetic Spectrum & Infrared Fundamentals2. The Infrared Threat3. Missile Warning Receivers4. Aircraft Signatures5. Infrared Missile System Principles6. DIRCM Systems– Increasing J/S Requirement– Legacy DIRCM (Broadband and Flash Lamp) Systems– Laser Jam (Closed Loop) DIRCM Systems

7. Test and Evaluation of DIRCM Systems

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Module 5 Overview

• How IR Missiles Work• Video – Basics of How IR Missiles Work• Threat Development Timeline & History• Missile Guidance Basics• Intro to IRCM Basics to Defeat IR Missiles

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

IR Missile Guidance Loop Description

Pointing Commands To Seeker Gyro

Reticle, Mirror/Gyro

Steering CommandsTo Fins

GuidanceProcessing

Precession

AMP EnvelopeCarrier

Band PassSpin

Band Pass

Detector

MODULATION • Tracks small targets (points sources)more efficiently than large sources

• Has problems with extended sharplydefined edges (horizon line)

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

IR Missile Threat Evolution

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

ScanningImagers

2000

1st Gen Staring Imagers

2005

2nd GenSpectral Imagers

2010

Threat Development Timeline vs. Band

1960s

Spin Scan

1970s

Con Scan Pseudo-Imagers

1990s

SA-7HN-5 Redeye SA-14

SA-16

1970/80s

CooledSeeker

Stgr-POSTSA-18Mistral

Stgr-BASIC

Band I(hot metal)

Band II(hot metal)

Band IV(jet engine plume)

1980s

FRCCM

reticle-based seekers

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

•• Pseudo ImagingPseudo Imaging•• Small FieldSmall Field--ofof--View Detector View Detector

Scanning a Rosette Pattern Using Scanning a Rosette Pattern Using TwoTwo--CounterCounter--Rotating Optical Rotating Optical ElementsElements

•• Small IFOVSmall IFOV–– Provides Greater SensitivityProvides Greater Sensitivity–– Resistant to JammersResistant to Jammers–– Resistant to False TargetsResistant to False Targets

RosetteRosette

Detector IFOV

PetalTargetImage

A Rosette Scanning Pattern

Normalized Signal PulseSequence for On-Axis Image

S(t)

1

0

Petal ScanTime

t

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

•• Produces an ImageProduces an Image•• Takes Advantage of StateTakes Advantage of State--ofof--thethe--Art TechnologyArt Technology

–– Processing CapabilityProcessing Capability–– Software Track AlgorithmsSoftware Track Algorithms

ImagingImaging

Linear Detector Array

Target Scene

Rectangular Detector Arrays

Target SceneImage

Rectangular Detector Arrayand Target Scene

Linear Detector Array Scanningof a Target Scene

Illustration of Imaging Detectors

© Copyright 2010 by John L. Minor, American Eagle Aerospace LLC.

Flare DecoyFlare Decoy

Objective: Present a more attractive IR target to the missile

•• ShortcomingsShortcomings--Flares operate at higher Flares operate at higher temperatures than aircraft, emitting temperatures than aircraft, emitting primarily in Bands 1 & 2 (versus primarily in Bands 1 & 2 (versus modern Band 4 threats)modern Band 4 threats)--Very effective against Band 1 & 2 Very effective against Band 1 & 2 (1(1stst and 2and 2ndnd Generation) missilesGeneration) missiles--Limited performance against newer Limited performance against newer Band 4 missiles due to output Band 4 missiles due to output energy limitations and inclusion of energy limitations and inclusion of flare CCM techniques in missile flare CCM techniques in missile designdesign