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HAPTER :HAPTER :

Thermal InfraredThermal InfraredRemote SensinRemote Sensin

REFERENCE: Remote SensingREFERENCE: Remote Sensing

of the Environmentof the Environment

John R. Jensen (2007)John R. Jensen (2007)

Second EditionSecond Edition

Pearson Prentice HallPearson Prentice Hall

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Thermal Infrared Remote SensingThermal Infrared Remote Sensing

Thermal infrared energy is emitted from all objectsthat have a temperature greater than absolute zero.

Therefore, all the features we encounter in the landscape on a

typical day (Sun, vegetation, soil, rocks, water, and even

people) emit thermal infrared electromagnetic radiation.

Humans eyes cannot detect differences in thermal infrared

from 400 to 700 nm. Our eyes are not sensitive to the

reflective infrared (700 nm - 3.0 m) or thermal infraredenergy (3.0 - 14 m).

The astronomer Sir Frederick William Herschel (1738-1822)

discovered the infrared portion of the electromagnetic spectrum in

History of Thermal InfraredRemote Sensing

1800 described in his famous paper Investigations of the Powers of

the Prismatic Colours to Heat and Illuminate Objects: with

Remarks.

In 1879, S. P. Langley began a research program to find a superior

radiation detector. One year later he invented the bolometer that was

able to obtain measurable temperature variations of 1/10,000 C.

In World War I, S. O. Hoffman could detect men at 120 m and

eventually aircraft.

In the 1930s, Germany developed the Kiel system for discriminating

between bombers and night fighters.

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The single most important development in infrared technology

was the development of the detector element by nations at war

during World War II. Early infrared detectors were lead salt

photodetectors.

Now we have very fast detectors consisting of mercury-doped

germanium (Ge:Hg), indium antimonide (InSb) and other

substances that are very responsive to infrared radiation. We also

have computers to rapidly process and display the thermal

radiometric measurements.

In 1968, the government declassified thermal infrared remote

sensing systems that did not exceed a certain spatial resolution and

temperature sensitivity.

The first declassified satellite remote sensor data were collected

b the U. S. Television IR O erational Satellite TIROS launched


in 1960. The coarse resolution thermal infrared data were ideal for

monitoring regional cloud patterns and frontal movement.

NASA launched the Heat Capacity Mapping Mission (HCMM)

on April 26, 1978 that obtained 600 x 600 m spatial resolution

thermal infrared data (10.5 - 12.6 m) both day (1:30 pm) and.

(geology) thermal infrared systems.

NASAs Nimbus 7 launched on October 23, 1978 had a Coastal

Zone Color Scanner (CZCS) that included a thermal infrared

sensor for monitoring sea-surface temperature.

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In 1980, NASA and the Jet Propulsion Laboratory developed the


t erma n rare mu t spectra scanner t at acqu res

thermal infrared energy in six bands at wavelength intervals of

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CharacteristicsCharacteristicsof a Thermalof a Thermal

InfraredInfraredAirborneAirborne

amplifier

high-density

magnetic

tape

hot

optional

film

recorder focusing

mirrors

dewar ofliquid

nitrogen

detector

recordermirror

modulated

light

source

motor

scan

mirror

AcrossAcross--tracktrackScannerScanner

H

calibration

source cold

source

radiant flux,

within the

instantaneous-field-

of-view,

total

angular

field-of-

view

D

Thermal Infrared Image of Effluent Enteringthe Savannah River Swamp System

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Kinetic Heat, Temperature,Kinetic Heat, Temperature,Radiant Energy and Radiant FluxRadiant Energy and Radiant Flux

The energy of particles of matter in random motion is called

, , .

objects having a temperature above absolute zero (0 K; -273.16 C;

and -459.69 F) exhibit this random motion. When these particles

collide they change their energy state and emit electromagnetic

radiation.

The amount of heat can be measured in calories (the amount of

eat requ re to ra se t e temperature o g o water . e can

measure the true kinetic temperature (Tkin) or concentration of this

heat using a thermometer. We perform this in situ temperaturemeasurement when we are ill. We can also measure the true kinetic

internal temperature of soil or water by physically touching them

with a thermometer.

Fortunately for us, an objects internal kinetic heat is also

converted to radiant energy (often called external or apparent


energy). The electromagnetic radiation exiting an object is called

radiant flux() and is measured in watts. The concentration ofthe amount of radiant flux exiting (emitted from) an object is its

radiant temperature (Trad).

There is usually a high positive correlation between the true

kinetic tem erature of an ob ect T and the amount of radiant n

flux radiated from the object (Trad). Therefore, we can utilize

radiometers placed some distance from the object to measure its

radiant temperature which hopefully correlates well with the

objects true kinetic temperature. This is the basis of thermal

infrared remote sensing.

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Unfortunately, the relationship is not perfect, with the

remote measurement of the radiant temperature always

being slightly less than the true kinetic temperature of the

object.

This is due to a thermal property called emissivit .

Methods of Heat TransferMethods of Heat Transfer

Pan

Conduction

in contactwith burnera.

Conduction occurs when one body(molecule or atom) transfers its

kinetic energy to another by collidingw ith it. This is how a pan is heated ona stove.

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Methods of Heat TransferMethods of Heat Transfer

Convection

Terrain

Pulseof

warmair

b.

In convection, the kinetic energy ofbodies is transferred from one place to

another by physically moving the bodies.An example is the convectional heating ofair in the atmosphere in the earlyafternoon.

Methods of Heat Transfer

Radiation

c.

EarthSun

Electromagneticwave

The transfer of energy by electromagnetic

sensing because it is the only form ofenergy transfer that can take place in avacuum such as the region between theSun and the Earth.

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Atmospheric Windows in theAtmospheric Windows in the

Electromagnetic SpectrumElectromagnetic Spectrum

Thermal Radiation LawsThermal Radiation Laws A blackbody is a theoretical construct that absorbs all the

radiant energy striking it and radiates energy at the

maximum possible rate per unit area at each wavelength for

any given temperature.

No objects in nature are true blackbodies, however, we

may think of the Sun as approximating a 6,000 K

blackbody and the Earth as a 300 K blackbody. If we

pointed a sensor at a blackbody we would be able to record

energy in specific wavelengths exiting the object and the

dominant wavelength of the object. In order to do this, we

utilize two important physical laws:

the Stefan-Boltzmann law and Weins displacement law.

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The total spectral radiant flux exitance (Mb) measured in watts m2

leaving a blackbody is proportional to the fourth power of its

temperature (T).

Stephen Boltzmann LawStephen Boltzmann Law

The Stefan-Boltzmann law is expressed as:

Mb = T4

where is the Stefan-Boltzmann constant equaling 5.6697 x 10-8 W

m-2 K-4, and Tis temperature in degrees Kelvin. The total radiant

exitance is the integration of all the area under the blackbody

.

The Sun produces more spectral radiant exitance (Mb) at 6,000 K

than the Earth at 300 K. As the temperature increases, the totalamount of radiant energy measured in watts per m2 (the area under

the curve) increases and the radiant energy peak shifts to shorter

wavelengths.

The Stefan-Boltzmann

Stephen Boltzmann LawStephen Boltzmann Law

spectral radiantexitance (Mb) leavinga blackbody isproportional to thefourth power of itstemperature (T).

Mb = T4

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WeinsWeins Displacement LawDisplacement Law

The relationship between the true temperature of a blackbody

(T) in degrees Kelvin and its peak spectral exitance or

dominant wavelength (max) is described by theWeins displacement law:

max = k = 2898 m KT T

where kis a constant equaling 2898 m K.


Wien's Law tells us that objects of different temperatureemit spectra that peak at different w avelengths.

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For example, the average temperature of the Earth is 300

K 80 F .


We compute the Earths dominant wavelength as:

max = 2898 m KT

max = 2898 m K = 9.67 m300 K

WHAT IS SUNS DOMINANT WAVELENGTH?

The dominant wavelength provides valuable information

about which part of the thermal spectrum we might want to


sense in. For example, if we are looking for 800 K forest

fires that have a dominant wavelength of approximately

3.62 m then the most appropriate remote sensing systemmight be a 3-5 m thermal infrared detector.

If we are interested in soil, water, and rock with ambienttemperatures on the earths surface of 300 K and a

dominant wavelength of 9.66 m, then a thermal infrareddetector operating in the 8 - 14 m region might be mostappropriate.

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BlackbodyBlackbodyRadiationRadiation

Curves forCurves forSeveralSeveral

ec sec sincluding theincluding theSun and EarthSun and Earth

Explain the hot spot?

This can of suds is ice coldstraight out of the fridge. When

Live image reveals truth.

The curtain is lifted and the truthrevealed. The paint on the outside

scanne w an n rare camerayou would expect the entire image

to be relatively even intemperature and to appear "cold"in relation to the background. Can

you explain the apparent "hot"spot in the center of the can.

Hint: it's not a fingerprint!

of the can has been scratched off ina small area. The bare aluminumhas a different emissivitythan the

painted aluminum. The camera canonly allow for one emissivitysetting

at one time so to the detector thebare aluminum "images" hotter than

the rest of the can.

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The world is not composed of radiating blackbodies. Rather

it is com osed of selectivel radiatin bodies such as rocks

Emissivity (Emissivity ())

soil, and water that emit only a fraction of the energy

emitted from a blackbody at the same temperature.

Emissivity, , is the ratio between the radiant flux exiting areal-world selective radiating body (Mr) and a blackbody at

the same temperature (Mb):

(Mb)etemperatursametheatblackbodyaofemittanceRadiant(Mr)objectanofemittanceRadiant=

All selectively radiating bodies have emissivities ranging

from 0 to

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Spectral emissivityof a blackbody, a

graybody, and a

hypothetical

1

0.5

ctralEmissivity,

selective radiator

blackbody

alEmissivity,

se ec ve ra a or0.1

0.1 1 10 100

106

108

Wavelength,m

Spe

Exitance

16,000 K

graybody

a.

Spectral radiant

exitance distribution

Spectr

tExitance

-1

0.1

100100101

102

104

Wavelength,m

SpectralRadiant

Wm

-2m

- ac o y

= 1.06,000 Kgraybody

= 0.1

6,000 K

selective radiator

b.

of the blackbody,graybody, and

hypothetical

selective radiatorSpectralRadia

n

Wm

-2u

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Two rocks lying next to one another on the ground could

have the same true kinetic temperature but have different

apparent temperatures when sensed by a thermalradiometer simply because their emissivities are different.

The emissivity of an object may be influenced by a number

factors, including:

color -- darker colored objects are usually better

absorbers and emitters (i.e. they have a higher emissivity)

than lighter colored objects which tend to reflect more of

the incident ener .

surface roughness -- the greater the surface roughness of

an object relative to the size of the incident wavelength, thegreater the surface area of the object and potential for

absorption and re-emission of energy.

moisture content -- the more moisture an object contains,the greater its ability to absorb energy and become a good

emitter. Wet soil particles have a high emissivity similar to

water.

compac on -- e egree o so compac on can e ec

emissivity.

field-of-view -- the emissivity of a single leaf measured with

a very high resolution thermal radiometer will have a

different emissivity than an entire tree crown viewed using a

coarse spatial resolution radiometer.

wavelength -- the emissivity of an object is generally

considered to be wavelength dependent. For example, while

the emissivity of an object is often considered to be constant

throughout the 8 - 14 mm region, its emissivity in the 3 -5 mm

region may be different.

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viewing angle - the emissivity of an object can vary with

sensor v ew ng ang e.

We must take into account an objects emissivity when we

use our remote radiant temperature measurement to

measure the objects true kinetic temperature.

This is done by applying Kirchoffs radiation law.

Remember that the terrain intercepts incident (incoming)

KirchoffsKirchoffs Radiation LawRadiation Law

ra an ux i . s nc en energy n erac s wterrain materials. The amount of radiant flux reflected

from the surface (r), the amount of radiant flux absorbedby the surface (

), and the amount of radiant flux

transmitted through the surface () can be carefully

measured as we apply the principle of conservation of

incident energy. The general equation for the interaction of

spectral() radiant flux with the terrain is:1 = i = r + +

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The Russian physicist Kirchhoff found that in the infraredportion of the spectrum the spectral emissivity of an object

generally equals its spectral absorptance, i.e. ~. This is


often phrased as:

good absorbers are good emitters and

good reflectors are poor emitters.

Also, most real-world materials are usually opaque to

thermal radiation meaning that no radiant flux exits from

the other side of the terrain element. Therefore, we may

assume transmittance, = 0. Substituting emissivity forabsorptance and removing transmittance from the

equation yields:

1 = r +

This simple relationship describes why objects appear as

they do on thermal infrared imagery. Because the terrain

does not lose any incident energy to transmittance, all of


the energy leaving the object must be accounted for by the

inverse relationship between reflectance (r) and emissivity().If reflectivity increases then emissivity must decrease. Ifemissivity increases then reflectivity must decrease. For

example, water absorbs almost all incident energy and

reflects very little. Therefore, water is a very good emitter

and has a high emissivity close to 1. Conversely, a sheetmetal roof reflects most of the incident energy, absorbs

very little, yielding an emissivity much less than 1.

Therefore, metal objects such as cars, aircraft, and metal

roofs almost always look very cold (dark) on thermal

infrared imagery.

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The goal of thermal infrared remote sensing is to be able to

point a radiometer at an object and have the apparent

radiant temperature recorded (Trad) equal the true kinetictemperature of the object (Tkin). Unfortunately, the radiant

flux from a real-world ob ect at a iven tem erature is not

the same as the radiant flux from a blackbody at the same

temperature largely due to the effects ofemissivity.

Knowing the emissivity characteristics of an object makes

it possible to modify the Stefan-Boltzmann law (originally

applicable to blackbodies) so that it pertains to the total

spectral radiant flux of real-world materials (Mr):

Mr= Tkin 4It takes into account the temperature of the object and its

emissivity to create a more accurate estimate of the radiant

flux exiting an object.

Thermal infrared remote sensing systems generally

record the apparent radiant temperature, Tradof the terrain

rather than the true kinetic tem erature, T . If we assume


that the incorporation of emissivity in the previous

equation has improved our measurement to the point that:

Mr = Tkin 4 and we assume thatMb = Trad

4 and

=r

b

,

Trad4 = Tkin 4

Therefore, the radiant temperature of an object recorded

by a remote sensor is related to its true kinetic temperature

and emissivity by the following relationship: Trad = 1/4Tkin

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Water, rocks, soil, vegetation, the atmosphere, and human

Thermal Properties of TerrainThermal Properties of Terrain

them (thermal conductivity) onto another surface and to

store heat (thermal capacity). Some materials respond to

changes in temperature more rapidly or slowly than others

(thermal inertia).

Thermal capacity (c) is the ability of a material to store

heat. It is measured as the number of calories required to

Thermal Properties of TerrainThermal Properties of Terrain

raise a gram of material (e.g. water) 1 C (cal g-1 C-1).

Water has the highest thermal capacity (1.00). It stores heat

very well relative to all the other materials.

Thermal conductivity (K) is the rate that heat will pass

through a material and is measured as the number of

calories that will pass through a 1-cm cube of material in 1

second when two opposite faces are maintained at 1 Cdifference in temperature (cal cm-1 sec-1 C). The

conductivity of a material is variable due to soil moisture

and particle size. Many rocks and soils are extremely poor

conductors of heat.

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Thermal inertia (P) is a measurement of the thermal

Thermal InertiaThermal Inertia

measured in calories per square centimeter per second

square root per degree Celsius (cal cm-2 sec -1/2 C-1).

Thermal inertia is computed using the equation:

P = (K x p x c)1/2

whereKis thermal conductivit , is densit ( cm-3), and c

is thermal capacity. Density is the most important property

in this equation because thermal inertia generally increaseslinearly with increasing material density.

It would be wonderful if we could remotely sense each of the

aforementioned variables and then simply compute thermal inertia.

Unfortunately, this is not the case because conductivity, density, and

Apparent Thermal InertiaApparent Thermal Inertia

thermal capacity must all be measured in situ. Nevertheless, it is possible

to remotely sense and compute an apparent thermal inertia measurement

per pixel in the following manner. A thermal infrared image is acquired

over the identical terrain in the nighttime and in the early afternoon. The

two images are geometrically and radiometrically registered to one

another and the change in temperature, Tfor a specific pixel is

determined by subtracting the nighttime apparent temperature from the

da time a arent tem erature. The a arent thermal inertia ATI er

pixel is:

ATI = 1 - A

T

withA being the albedo (reflectance) measured in a visible band of the

spectrum for the pixel of interest.

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Thermal InfraredThermal Infrared

Data CollectionData Collection

Thermal infrared remote sensor data may be collected by:

across-track thermal scanners, and

push-broom linear and area array charge-coupled

device CCD detectors.

Thermal InfraredThermal InfraredMultispectral ScannersMultispectral Scanners

- , - ,

Scanner

These scanners provide most of the useful high spatial and

spectral resolution thermal infrared data for monitoring the

environment. The DS-1260 records data in 10 bands

including a thermal-infrared channel (8.5 to 13.5 m). The

DS-1268 incorporates the thematic mapper middle-infraredbands (1.55 - 1.75 m and 2.08 - 2.35 m). The AMS contains

a hot-target, thermal-infrared detector (3.0 to 5.5 m) in

addition to the standard thermal-infrared detector (8.5 to

12.5 m).

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Thermal InfraredThermal Infrared

Multispectral ScannersMultispectral Scanners

The diameter of the circular ground area viewed by the

sensor,D, is a function of the instantaneous-field-of-view, , ofthe scanner measured in milliradians (mrad) and the altitude

of the scanner above ground level,H, where:

D = H xFor example, if the IFOV of the scanner is 2.5 mrad, the

ground size of the pixel in meters is a product of the IFOV

(0.0025) and the altitude above ground level (AGL) in meters.

IFOVs range from 0.5 to 5 milliradians

CharacteristicsCharacteristicsof a Thermalof a Thermal

InfraredInfraredAirborneAirborne

amplifier

high-density

magnetic

tape

hot

optional

film

recorder focusing

mirrors

dewar of

liquid

nitrogen

detector

recorder

mirror

modulated

light

source

motor

scan

mirror

AcrossAcross--tracktrackScannerScanner

H

calbrat on

source cold

source

radiant flux,

within the

instantaneous-field-

of-view,

total

angular

field-of-

view

D

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Ground Resolution Cell Size Along aGround Resolution Cell Size Along aSingle AcrossSingle Across--Track ScanTrack Scan

Thermal infrared detectors are usually composed of:

In:Sb indium antimonide with a eak sensitivit

Thermal Infrared DetectorsThermal Infrared Detectors

near 5m;

Gd:Hg (mercury-doped germanium) with a peak

sensitivity near 10 m, or

Hg:Cd:Te (mercury-cadmium-telluride) sensitive

over the range from 8 - 14 m.

The detectors are cooled to low temperatures (-196 C; -243

C; 73 K) using liquid helium or liquid nitrogen. Cooling the

detectors insures that the radiant energy (photons) recorded

by the detectors comes from the terrain and not from the

ambient temperature of objects within the scanner itself.

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Peak Sensitivity ofIndium-Antimonide1011

1012

In:Sb

(Indium

Antimonide)

-

Germanium Thermal

InfraredDetectors

109

1010

RelativeResponse

Ge:Hg

(Mercury-doped

Germanium)

1 1.5 2 3 4 5 6 7 8 10 15 20108

Wavelength,m

There is an inverse relationship between having high spatial

resolution and high radiometric resolution when collecting

Thermal Infrared Remote SensingThermal Infrared Remote Sensing

.

The larger the radiometer instantaneous-field-of-view,, the longer thedwell time that an individual detector can view the terrain within the

IFOV during a single sweep of the mirror. A larger IFOV provides good

radiometric resolution which is the ability to discriminate between very

small differences in radiant energy exiting the terrain element. In fact,

the radiant energy signal measured may well be much stronger than any

no se n ro uce rom e sensor sys em componen s. en s a esplace we say that we have a good signal to noise ratio. Of course, the

larger the IFOV, the poorer the ability to resolve fine spatial detail.

Selecting a smaller IFOV will increase the spatial resolution. But, the

sensor will dwell a shorter time on each terrain element during a sweep

of the mirror, resulting in poorer radiometric resolution and perhaps a

poorer signal to noise ratio.

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InverseInverse--Square LawSquare Law

point source quadruples the infrared energy received by that

detector. The inverse-square law states that:

the intensity of radiation emitted from a point source varies

as the inverse square of the distance between source and

receiver.

Thus, we can obtain a more intense, strong thermal infrared

signal if we can get the remote sensor detector as close to theground as practical.

D2

D1

Inverse-square Law

remotedetectors

The intensity ofthermal

radiation

emitted from a

d

2d

Blackbody Point Source, S

1 cm2 po nt source, ,

varies as the

inverse square of

the distance, d,

between the

source and

receiver,D1 or

D2

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Most thermal infrared remote sensing investigations try tomaintain good radiometric and spatial resolution by:

ConsiderationConsideration

selecting a fairly large IFOV such as 2.5 mrad, and

flying at a relatively low altitude to obtain smaller pixel

sizes.

Unfortunately, at lower altitudes, the high spatial resolution

may be outweighed by the fact that more flight lines are

requ re o cover e area compare o more e c en

coverage at higher altitudes with larger pixels. The pixel size

and the geographic size of the survey are considered,objectives are weighed, and a compromise is reached.

Multiple flight lines of aircraft MSS data are difficult to

mosaic.

Thermal infrared scanning systems (actually all scanning

Geometric Correction of AcrossGeometric Correction of Across--TrackTrackThermal Infrared Scanner DataThermal Infrared Scanner Data

systems) introduce numerous types ofgeometric errorthat

must be understood because they impact a) the quality of the

imagery for visual or digital image processing and analysis,

and b) the creation of planimetric maps from the thermal

infrared data. The most important considerations are:

spatial resolution cell size;

tangential scale distortion, and

one-dimensional relief displacement.

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Perspective Geometry of a Vertical AerialPerspective Geometry of a Vertical AerialPhotographPhotograph

and Acrossand Across--track Onetrack One--dimensional Reliefdimensional ReliefDisplacementDisplacementand Tangential Scale Distortionand Tangential Scale Distortion

DaytimeOptical

andNighttime

InfraredImageryof New

York City

ThermalInfrared

AerialPhotograph

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Radiometric Calibration ofRadiometric Calibration of

Thermal Scanner DataThermal Scanner Data

purposes such as temperature mapping, it is necessary to

calibrate the brightness values stored on the digital tape to

temperature values. This radiometric calibration may be

performed using:

internal blackbod source referencin or

external empirical referencing based on in situ datacollection.

External Empirical ReferencingExternal Empirical Referencingof Thermal Infrared Imageryof Thermal Infrared Imagery

100

80

60

40

100

80

60

40

diometricallyUncalibrated

SensingBrightnessValue,

BVij

4020

0

20

60 80 4020

0

20

60 80

BVij = -0.0148x2 + 2.1157x + 26.303

R2 = 0.9895

In situ True Kinetic Temperature Measurement, T kin

a. b.0 0

Linear Non-linear: 2nd Order Polynomial

BVij = 0.6586x + 56.173

R2 = 0.8631

R

Remo

t

In situ True Kinetic Temperature Measurement, T kin

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It is possible to make both linear and area arrays that are sensitive to mid- and

thermal infrared radiation. Linear and area arrays allow improved thermal

PushPush--broom Linear and Area Arraybroom Linear and Area ArrayChargeCharge--coupled device (CCD) Detectorscoupled device (CCD) Detectors

the solid-state microelectronic detectors are smaller in size (e.g. 20 x 20 mm) and

weight, require less power to operate, have fewer moving parts, and are more

reliable;

each detector in the array can view the ground resolution element for a longer

time (i.e. it is as longer dwell time), allowing more photons of energy from within

the IFOV to be recorded by the individual detector resulting in improved

radiometric resolution (the ability to resolve smaller temperature differences);

each detector element in the linear or area array is fixed relative to all otherelements therefore the geometry of the thermal infrared image is much improved

relative to that produced by an across-track scanning system; and

some linear and area thermal detectors do not even require the cooling

apparatus.

ForwardForward--Looking Infrared (FLIR)Looking Infrared (FLIR)SystemsSystems

For decades, the military organizations throughout the world

have funded the development of FLIR type systems that look

obliquely ahead of the aircraft and acquire high-quality thermal

infrared imagery, especially at night.

FLIR systems collect the infrared energy based on the same

pr nc p es as an across-trac scanner prev ous y scusse ,except that the mirror points forward about 45 and projects

terrain energy during a single sweep of the mirror onto a linear

array of thermal infrared detectors.

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ForwardForwardLookingLooking

InfraredInfrared(FLIR)(FLIR)xamp esxamp es

The diurnal cycle encompasses 24 hours. Beginning at sunrise, the earth

begins intercepting mainly short wavelength energy (0.4 - 0.7 m) from

Diurnal Temperature CycleDiurnal Temperature Cycleof Typical Materialsof Typical Materials

. ,

incoming short wavelength energy and reflects much of it back into the

atmosphere where we can use optical remote sensors to measure the

reflected energy. However, some of the incident short wavelength energy

is absorbed by the terrain and then re-radiated back into the atmosphere

as thermal infrared long wavelength radiation (3 - 14 m). The outgoinglongwave radiation reaches its highest value during the day when the

surface temperature is highest. This peak usually lags two to four hours

after the midday peak of incoming shortwave radiation, owing to the timetaken to heat the soil. The contribution of reflected short wavelength

energy and emitted long wavelength energy causes an energy surplus to

take place during the day. Both incoming and outgoing shortwave

radiation become zero after sunset (except for light from the moon and

stars), but outgoing longwave radiation continues all night.

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Peak Period ofPeak Period of

Daily OutgoingDaily OutgoingLongwaveLongwave

the Diurnalthe DiurnalRadiantRadiant

Temperature ofTemperature ofSoils and Rocks,Soils and Rocks,

Ve etationVe etationWater, Moist SoilWater, Moist Soil

and Metaland MetalObjectsObjects

Nighttime Thermal InfraredNighttime Thermal Infrared

Imagery of an AirportImagery of an Airport

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LL--BAND ANTENNABAND ANTENNA

NOAA 12/14

NOAA 15/16

Advanced Very High Resolution RadiometerAdvanced Very High Resolution Radiometer

((AVHRR)AVHRR)

11 0.580.58--0.680.68

22 0.720.72--1.101.10

33 3.553.55--3.933.93

44 10.510.5--11.511.5

55 11.511.5--12.512.5

Sea Surface Temperature (SST)Sea Surface Temperature (SST)

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SatelliteNumber

LaunchDate

AscendingNode

DescendingNode Service Dates

TIROS-N 10/13/1978 1500 300 10/19/78 - 01/30/80

NOAA-6 6/27/1979 1930 730 06/27/79 - 11/16/86

TEMPORAL COVERAGE OF AVHRR

NOAA-7 6/23/1981 1430 230 08/24/81 - 02/01/85

NOAA-8 3/28/1983 1930 730 05/03/83 - 10/31/85

NOAA-9 12/12/1984 1420 220 02/25/85 - 11/07/98

NOAA-10 9/17/1986 1930 730 11/17/86 - 09/16/91 (still on standby)


NOAA-12 5/14/1991 1930 730 09/16/91 - 12/14/98


NOAA-14 12/30/1994 1340 140 12/30/94 - Present

NOAA-15 5/13/1998 1930 730 05/13/98 - Present

NOAA-16 9/21/2000 1340 140 Present

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LAKE SUPERIORLAKE SUPERIOR

MCSST Algorithm

Daytime Pass:

o = * * -

Nighttime Pass:

SST (oC) = a*T4 +b*(T3-T5) + c

Where,

T3 = Brightness Temperature at Channel 3T4 = Brightness Temperature at Channel 4T5 = Brightness Temperature at Channel 5

a, , c = e g ng oe c en s

Reference: McClain, E.P., W.G. Pichel, and C.C. Walton. (1985)Comparat ive per formance of AVHRR-Based Multichanne l SeaSurface Temperature, Journal of Geophysical Research.90(11):11587-11601

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A New Set of MCSST Equations for NOAA-9/ AVHRR

SHOICHI KIZU1 and FUTOKI SAKAIDA2

1Department of Geophysics, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-77, Japan2Ocean Mechanical Engineering Chair, Kobe University of Mercantile Marine,5-1-1 Fukae-Minami-machi Hi ashi-Nada-ku Kobe 658 Ja an(Rece ived 24 July 1995; in revised form 26 October 1995;accepted 27 October 1995)

A new set of mult i-channel sea surface temperature (MCSST) equat ions for theAdvanced Very High Resolut ion Radiometer (AVHRR) on NOAA-9 is derivedfrom regression analyses between two-channel brightness temperatures andin situSST obta ined from moored buoys around Japan.Two equations are derived:onefor daytime and the other for n ight time .Theyare l inea r spl it w indow type and boththe equat ions conta in a term dependent on sate l li te zenith angle ,w hich has notbeen accounted for in the previous dayt ime spli t window equations for NOAA-9.I t i s shown tha t the new set o f equat ion can g ive SSTs in much bet te r p reci sion thanthose without the zenith-angle-dependent terms.It is a lso found that the sp li twindow equation for NOAA-9 provided by the Nationa l Oceanographic andAtmospheric Administration/National Environmental Satellite, Data and Information

rv r y u r y ;sometimes nighttime SSTs are even higherthan dayt ime SSTs.This is because thezenith angle effect to the rad iat ion defic it is neglected in the dayt ime equation byNOAA/NESDIS. By using the new MCSST equations, i t is expected that the qual i ty

of sate l li te MCSST would be much improved,at least in regiona l app l icationsaround Japan,for the period of NOAA-9s operat ion.

Journal of OceanographyVol. 52, pp. 235 to 249. 1996

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Sea Surface TemperatureSea Surface Temperature

ASTER (Advanced Spaceborne Thermal Emission and ReflectionRadiometer) is an imaging instrument that is flying on Terra, a satellite

launched in December 1999 as part of NASA's Earth Observing System(EOS). ASTER is a cooperative effort between NASA and Japan's Ministryof Economy, Trade and I ndustry (METI) and the Earth Remote SensingData Analysis Center (ERSDAC). ASTER w ill be used to obtain detailedmaps of land surface temperature, emissivity, reflectance and elevation.The EOS platforms are part of NASA's Earth Science Enterprise, whosegoal is to obtain a better understanding of the interactions between thebiosphere, hydrosphere, lithosphere and atmosphere.

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The cur rent e ruption o f Mt. Etnas tart ed on July 17, 2001and hascont inued to the present (august3 , 2001) . Thi s ASTER image wasacqui red on Sunday , July 29 andshows advanci ng lava flows onthe southern flank of Mt. Etnaabove the town of Nicolosi,which is potentially threatened ifthe eruption increases inmagnitude. Also visible arelow in summit craters above

the main l ava flows, and a sma llf issure eruption. The bright puffycl ouds were formed f rom water

vapor released during theeruption. The image covers anarea of 24 x 30 km.

On April 3, 2000 ASTERcaptured this image of theerupting Mt. Usu vo lcano inHokka ido, Japan. This falsecolor infrared image,covering an area of 18 km(13 miles) by 22 km (15miles , of Mt Usu volcano is

dominated by Lake Toya, anancient volcanic caldera.

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On April 5 ASTER capturedthis night time thermalinfrared image of M t. Usu.Hot thermal anomalies,appearing as b righ t spo ts,are seen on the w est flankof Usu, site of theeru tions. Additional hotspots appear at thesummit, and at a vent on

the east f lank.

LEFT: A J anuary 6, 2002 ASTER nighttime thermal infrared image of Chiliquesvo lcano in Ch il e shows a hot spo t in the summi t c ra te r and severa l o thers a long theupper f lanks of the edif ice, indicating new volcanic act ivity.

RIGHT: The day time image was acqui red on November 19, 2000 and was created byd isplay ing ASTER bands 1 ,2 and 3 in b lue, g reen and red . The n ight time image wasacqui red January 6 , 2002, and i s a color -coded d isplay o f a s ingle thermal inf ra redband. The hot test areas are white, and colder areas are darker shades of red.

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