Basic radiometry and SNR equations for CCD, ICCD...

Basic radiometry and SNRequations for CCD, ICCD and

EMCCD imagersUrban Brandstrom,1

1 Swedish Institute of Space Physics, Kiruna, Sweden

Presentation at:

http://alis.irf.se/˜urban/AGF351/Braendstroem-UNIS.pdf

UNIS 2011-11-15 – p. 1

http://alis.irf.se/~urban/AGF351/Braendstroem-UNIS.pdf

In memoriam

Professor Ingrid Sandahl (1949-2011)UNIS 2011-11-15 – p. 2

This is about taking pictures ofdarkness, or. . .

UNIS 2011-11-15 – p. 3

“Hunting photons with a spoon”

UNIS 2011-11-15 – p. 4

Radiometry

UNIS 2011-11-15 – p. 5

Radiometry vs. photometryHolst [1998] defines the term radiometry, as the

“energy or power transfer from a source toa detector”

UNIS 2011-11-15 – p. 6



while photometry is defined as

“the transfer from a source to a detectorwhere the units of radiation have beennormalised to the spectral sensitivity ofthe eye.”

UNIS 2011-11-15 – p. 6



while photometry is defined as

“the transfer from a source to a detectorwhere the units of radiation have beennormalised to the spectral sensitivity ofthe eye.”

Unfortunately the term photometry is often usedinstead of radiometry

UNIS 2011-11-15 – p. 6

Radiometry“Mathematics is often called the queen of thesciences. Radiometry should then be called thewaiting maid or servant. It is not especially elegant;it is not very popular, has not been trendy; but it isessential in almost every part of opticalengineering.” Wolfe [1998]

UNIS 2011-11-15 – p. 7

Solid angleThe solid angle Ω sweeps out the area A on theunit sphere (4π)

Ω =A

r2[sr]

Think of it as a 3D generalisation of the radian(arc length on the unit circle)

UNIS 2011-11-15 – p. 8

FluxPhoton flux:

Φγ =∂N

∂t

[

photons

s

]

in energy units:

ΦE =hc

λ

∂N

∂t[W]

UNIS 2011-11-15 – p. 9

RadianceAlso known as radiant steranceIn energy units:

LE =∂2Φ(λ)

∂As∂Ω

[

W

m2 sr

]

In quantum units:

Lγ =λ

hcLE

[

photons

s m2 sr

]

UNIS 2011-11-15 – p. 10

Spectral radianceAlso known as spectral radiant steranceIn energy units:

LλE =∂L

∂λ

[

W

m2 µm sr

]

In quantum units:

Lλγ =λ

hcLλE

[

photons

s m2 µm sr

]

UNIS 2011-11-15 – p. 11

Spectral radiant emittanceAlso known as spectral radiant exitance

Mλγ =∂Φ

∂As

=

[

photons

s m2

]

Flux per source area.What you get from a calibration source.In energy units:

MλE =hc

λMλγ

[

W

m2 µm sr

]

UNIS 2011-11-15 – p. 12

Spectral irradianceAlso known as spectral radiant incidance

Eλe =∂Φ

∂A=

[

photons

s m2

]

Flux per detector area.What you get on a detector (or whatever)In energy units:

EλE =hc

λEλγ

[

W

m2 µm sr

]

UNIS 2011-11-15 – p. 13

Transmittance

T =∏

∀X

TX(λ) = TaToTf . . .

UNIS 2011-11-15 – p. 14

IrradianceAt apperture:

Eγapp=

Φγapp

Aapp

=LγAsTaΩds

Aapp

=

[

photons

s m2

]

At image plane (assuming circular apperture):

Eγi=

Φγapp

Ai

= Lγ

As

Ai

Tπd2

app

4r2s

=

[

photons

s m2

]

(1)

UNIS 2011-11-15 – p. 15

Photometric units

Φv = KM

∫ 750nm

380nm

V (λ)Mp(λ)dλ [lm]

scoptic—rods photoptic—cones After Holst [1998]

UNIS 2011-11-15 – p. 16

Photometric units

scoptic—rods (KM = 1746 lm/W) photoptic—cones(K = 683 lm/W) After Holst [1998]

UNIS 2011-11-15 – p. 17

Photometric unitsΦv lm luminous fluxLv cd/m2 or nits luminanceMv lux or lm/m2 luminous emmitanceEv lux or lm/m2 illumniance

UNIS 2011-11-15 – p. 18

The foot-lambertA foot-lambert or footlambert (fL, sometimes fl orft-L) is a unit of luminance in U.S. customaryunits and some other unit systems. Afoot-lambert equals 1/π candela per square foot,or 3.426 candela per square meter (thecorresponding SI unit).

1 [ftL] =1

π

[

cd

ft2

]

≈ 3.426

[

cd

m2

]

UNIS 2011-11-15 – p. 19

The Rayleigh

UNIS 2011-11-15 – p. 20

The Rayleigh (1)Consider a cylindrical column of cross-sectionalarea 1 m2 extending away from the detector intothe source.The volume emission rate from a volumeelement of length dl at distance l isǫ(l, t, λ) photons m−3 s−1. The contribution to Lγ isgiven by:

dLγ =ǫ(l, t, λ)

4πdl

[

photons

s m2 sr

]

(2)

UNIS 2011-11-15 – p. 21

The Rayleigh (2)Integrating along the line of sight l [m]:

4πLγ =

∫ ∞

0

ǫ(l, t, λ)dl(3)

This quantity is the column emission rate, whichHunten et al. [1956] proposed as a radiometric unitfor the aurora and airglow.

UNIS 2011-11-15 – p. 22

The Rayleigh (3)In SI-units the Rayleigh becomes[Baker and Romick, 1976]:

1 [Rayleigh] ≡ 1 [R] , 1010

[

photons

s m2 (column)

]

(4)

The word column denotes the concept of anemission-rate from a column of unspecifiedlength, as discussed above. It should be notedthat the Rayleigh is an apparent emission rate,not taking absorption or scattering into account.

UNIS 2011-11-15 – p. 23

The Rayleigh (4)However (unfortunately. . . )

“the Rayleigh can be used as defined without anycommitment as to its physical interpretation, eventhough it has been chosen to make interpretationconvenient.” Hunten et al. [1956]

And then there is the clarifications by: Baker[1974]; Baker and Romick [1976]; Chamberlain [1995]

UNIS 2011-11-15 – p. 24

By now you should realizedthat. . .

UNIS 2011-11-15 – p. 25

. . . God said:Go to, let us go down, and there confound theirlanguage, that they may not understand oneanother’s speech. [Bible Gen11:7]

UNIS 2011-11-15 – p. 26

. . . God said:Go to, let us go down, and there confound theirlanguage, that they may not understand oneanother’s speech. [Bible Gen11:7]And there was: stilb, Rayleighs, footlamberts, Irradiance,spectral-radiant sterance, lumens, lux, candela, radiometry,nit, luminance, illuminance, emittance, apostilb, phot, skot,lambert, foot-candle, photometry, DIN, ASA, ISO. . .

UNIS 2011-11-15 – p. 26

. . . God said:Go to, let us go down, and there confound theirlanguage, that they may not understand oneanother’s speech. [Bible Gen11:7]And there was: stilb, Rayleighs, footlamberts, Irradiance,spectral-radiant sterance, lumens, lux, candela, radiometry,nit, luminance, illuminance, emittance, apostilb, phot, skot,lambert, foot-candle, photometry, DIN, ASA, ISO. . .

—Help! We are sinking!

UNIS 2011-11-15 – p. 26

and now. . .

UNIS 2011-11-15 – p. 27

The 4π confusion

UNIS 2011-11-15 – p. 28

The 4π confusionTherefore, we propose that photometricmeasurements of the airglow and aurora bereported in terms of 4πB rather than the surfacebrightness B itself. Further, we suggest that 4πB

be given the unit “rayleigh” (symbol R), where B isin units of 106 quanta cm−2 s−1 sr−1. Hence1 R = 106 quanta cm−2 (column)−1 s−1.

Hunten et al. [1956]

UNIS 2011-11-15 – p. 29

The 4π confusionTherefore, we propose that photometricmeasurements of the airglow and aurora bereported in terms of 4πB rather than the surfacebrightness B itself. Further, we suggest that 4πB

be given the unit “rayleigh” (symbol R), where B isin units of 106 quanta cm−2 s−1 sr−1. Hence1 R = 106 quanta cm−2 (column)−1 s−1.

Hunten et al. [1956]

So does both Hunten et al. [1956] and Chamberlain[1995] claim that 4π × 106 = 106 ???

UNIS 2011-11-15 – p. 29

Can we agree on this?The apparent radiance (Lγ) can be obtained fromthe column emission rate I (in Rayleighs)according to Baker and Romick [1976]:

Lγ =1010I

4π

[

photons

s m2 sr

]

(5)

UNIS 2011-11-15 – p. 30

Can we agree on this?The apparent radiance (Lγ) can be obtained fromthe column emission rate I (in Rayleighs)according to Baker and Romick [1976]:

Lγ =1010I

4π

[

photons

s m2 sr

]

(7)

Or is it:

Lγ = 1010I

[

photons

s m2 sr

]

(8)

UNIS 2011-11-15 – p. 30

Still confused. . .

. . . but at a different level.UNIS 2011-11-15 – p. 31

Signal

UNIS 2011-11-15 – p. 32

Where are my photons?• Transmittance (atmosphere, optics, filters. . . )

UNIS 2011-11-15 – p. 33

Where are my photons?• Transmittance (atmosphere, optics, filters. . . )• Apperture of the optics

UNIS 2011-11-15 – p. 33

Where are my photons?• Transmittance (atmosphere, optics, filters. . . )• Apperture of the optics• Area of detector (pixel-area for imagers)

UNIS 2011-11-15 – p. 33

Where are my photons?• Transmittance (atmosphere, optics, filters. . . )• Apperture of the optics• Area of detector (pixel-area for imagers)• Number of photoelectrons collected in a pixel

ne−γ= QE(λ)Eγi

tintApix

[

e−]

(15)

UNIS 2011-11-15 – p. 33


ne−γ= QE(λ)Eγi

tintApix

[

e−]

(17)

ne−γ≈ QE(λ)TtintApix

1010I

16f 2#

[

e−]

(18)

UNIS 2011-11-15 – p. 33

Noise

UNIS 2011-11-15 – p. 34

What is noise?

UNIS 2011-11-15 – p. 35

Some peoples noise are otherpeoples signal

UNIS 2011-11-15 – p. 36

Notation〈X〉2 variance of X

〈X〉 standard deviation of X

X mean value of X

Photon arrival is Poisson distributedIt can be shown that for a Poisson distributedsignal variance is equal to the mean

UNIS 2011-11-15 – p. 37

CCD principle of operation

After Janesick et al. [1987]UNIS 2011-11-15 – p. 38

E2V TECH CCD201

UNIS 2011-11-15 – p. 39

What is the SNR of an idealphoton detector?

UNIS 2011-11-15 – p. 40

CCD-noise sources

UNIS 2011-11-15 – p. 41

CCD noise

〈ne−CCD〉 =

√

〈ne−s〉2 + 〈ne−r

〉2 + 〈ne−p〉2

[

e−RMS

]

(19)

UNIS 2011-11-15 – p. 42

Shot Noise

〈ne−s〉 =

√

CTEN

(

〈ne−γ〉2 + 〈ne−d

〉2)

=(20)

=

√

CTEN

(

ne−γ+ ne−d

)

≈(21)

≈√

ne−γ+ ne−d

(22)

UNIS 2011-11-15 – p. 43

CCD Noise sources

After Holst [1998]UNIS 2011-11-15 – p. 44

Pattern Noise

〈ne−p〉 =

√

〈ne−FPN〉2 + 〈ne−PRNU

〉2 ≈ 〈ne−PRNU〉 ≈(23)

≈ Une−γ≈

ne−γ√ne−max

[

e−RMS

]

(24)

UNIS 2011-11-15 – p. 45

CCD Noise

〈ne−CCD〉 ≈

√

ne−γ+ ne−d

+ 〈ne−r〉2

[

e−RMS

]

(25)

UNIS 2011-11-15 – p. 46

Signal-to-noise ratio for a CCD• Measured signal-to-noise ratio:

SNRCCD =DN signal

DN noise

≈ne−γ

〈ne−CCD〉(26)

UNIS 2011-11-15 – p. 47


SNRCCD =DN signal

DN noise

≈ne−γ

〈ne−CCD〉(29)

• thus for a CCD:

SNRCCD ≈ne−γ

√

ne−γ+ ne−d

+ 〈ne−r〉2

(30)

UNIS 2011-11-15 – p. 47


SNRCCD =DN signal

DN noise

≈ne−γ

〈ne−CCD〉(32)

• thus for a CCD:

SNRCCD ≈ne−γ

√

ne−γ+ ne−d

+ 〈ne−r〉2

(33)

• and for an ideal photon detector:

SNRγideal =√

ne−γ(34) UNIS 2011-11-15 – p. 47

Threshold of detectionThe threshold of detection is usually defined asSNR = 2 while the Noise Equivalent ExposureNEE , is obtained when SNR = 1. For a CCD themaximum signal, or Saturation EquivalentExposure, SEE is obtained when the charge wellcapacity ne−max

[e−], is reached. This occurs when:

ne−γ≥ ne−max

− ne−d(35)

In most cases the maximum charge-well capacityDN SEE [counts], is matched to the maximumADC output DN max.

UNIS 2011-11-15 – p. 48

Dynamic range (1)The Dynamic Range is defined as the peaksignal divided by the RMS noise and theDC-bias-level, (if any). The minimum ADCoutput, is subtracted in the case of a signedinteger output. DR is usually expressed indecibels.

DR = 20 log10

(

DN SEE − DN min

DN DC + DN NEE − DN min

)

[dB]

(36)

UNIS 2011-11-15 – p. 49

Dynamic range (2)An approximate theoretical value for DR isobtained by dividing the maximum signal by thetotal noise

DR ≈ 20 log10

ne−max− ne−d

〈ne−tot〉 [dB](37)

UNIS 2011-11-15 – p. 50

ICCD

UNIS 2011-11-15 – p. 51

ICCD

After Holst [1998]UNIS 2011-11-15 – p. 52

SNR for a CCD• Measured signal-to-noise ratio:

SNRCCD =DN signal

DN noise

≈ne−γ

〈ne−CCD〉

UNIS 2011-11-15 – p. 53


SNRCCD =DN signal

DN noise

≈ne−γ

〈ne−CCD〉

• For an ideal photon detector:

SNRγideal =√

ne−γ

UNIS 2011-11-15 – p. 53


SNRCCD =DN signal

DN noise

≈ne−γ

〈ne−CCD〉

• For an ideal photon detector:

SNRγideal =√

ne−γ

• and for a CCD:

SNRCCD ≈ne−γ

√

ne−γ+ ne−d

+ 〈ne−r〉2 UNIS 2011-11-15 – p. 53

SNR for an ICCDNoting that for an ICCD:

ne−γ,pc≈ QEpc

(λ)TtintM2FOApix

1010I

16f 2#

[

e−RMS

]

UNIS 2011-11-15 – p. 54

SNR for an ICCD• The signal-to-noise ratio for an ICCD can be

estimated as:

SNRICCD ≈ne−γ,pc

√

k2MCP (ne−γ,pc

+ ne−d,pc) +

ne−

d+〈n

e−

r〉2

g2

UNIS 2011-11-15 – p. 55

SNR for an ICCD• The signal-to-noise ratio for an ICCD can be

estimated as:


√

k2MCP (ne−γ,pc

+ ne−d,pc) +

ne−

d+〈n

e−

r〉2

g2

• As seen, increasing the gain of the imageintensifier makes the CCD noise-sourcesnegligible, but does not increase the SNR

beyond that. For very high gain, we see that:


√

2(ne−γ,pc+ ne−d,pc

) UNIS 2011-11-15 – p. 55

SNR for an emCCDThe signal-to-noise ratio for anelectron-multiplication CCD can be estimated as:

SNRemCCD ≈ne−γ

√

k2em (ne−γ

+ ne−d+ 〈ne−cic

〉2) +〈n

e−

r〉2

g2

Please note:For an EMCCD kem ≈

√2 while kMCP (ICCD) is

taken as√

2 here, which is somewhat too good tobe true. In real cases kMCP ≥ 1.6

UNIS 2011-11-15 – p. 56

SNR example: CCD vs. ICCD

0.1

1

10

100

1000

10000 100000 1e+06 1e+07 1e+08 1e+09 1e+10

SN

R

Column emission rate Rayleighs 557.7 nm

t=16.7 ms, T=0.5, f/3.9, ALIS CCDCAM5, PAI ICCD

Ideal CCD (a)ALIS CCD (b)

PAI ideal CCD (c)PAI ICCD (d)PAI CCD (e)

UNIS 2011-11-15 – p. 57

SNR vs. of integration time

0.1

1

10

100

1000

10000

0.001 0.01 0.1 1 10 100 1000 10000

SN

R

Integration time [s]

T=0.5, f/3.5, ALIS CCDCAM5 557.7 nm

1 MR (a) 100 kR (b) 10 kR (c) 1 kR (d)

100 R (e)

UNIS 2011-11-15 – p. 58

Where are my photons?• Transmittance (atmosphere, optics, filters. . . )

UNIS 2011-11-15 – p. 59

Where are my photons?• Transmittance (atmosphere, optics, filters. . . )• Apperture of the optics

UNIS 2011-11-15 – p. 59

Where are my photons?• Transmittance (atmosphere, optics, filters. . . )• Apperture of the optics• Area of detector (pixel-area for imagers)

UNIS 2011-11-15 – p. 59


ne−γ= QE(λ)Eγi

tintApix

[

e−]

(44)

ne−γ≈ QE(λ)TtintApix

1010I

16f 2#

[

e−]

(45)

UNIS 2011-11-15 – p. 59

SNR and on-chip binning

0.1

1

10

100

1000

1 100 10000 1e+06 1e+08 1e+10

SN

R


t=1 s, T=0.5, f/3.5, ALIS CCDCAM5, PAI ICCD

bin 1,1 (a)bin 2,2 (b)bin 4,4 (c)bin 8,8 (d)

bin 16,16 (e)

UNIS 2011-11-15 – p. 60

SNR: CCD, ICCD and emCCD

0.1

1

10

100

1000

1000 10000 100000 1e+06 1e+07 1e+08 1e+09 1e+10

SN

R


t=1/25 s, T=0.5, f/1.6, bin=1x1

Ideal SI003AB (a)SI003AB (b)

Ideal PAI CCD (c)PAI ICCD (d)

Ideal CCD201-20 (g)CCD201-20 (h)

bin 2,2 CCD201-20 (h)

UNIS 2011-11-15 – p. 61

When do we need EM-gain?

UNIS 2011-11-15 – p. 62

Fast: ≈ 2900 photons/pixel

0.01

0.1

1

10

100

1 10 100 1000 10000

SN

R

photons/pixel (assuming 90% QE)

EM ON vs. EM OFF at 10 MHz

Ideal CCD201-20EM OFF 10 MHz CCD201-20EM ON 10 MHz CCD201-20

UNIS 2011-11-15 – p. 63

Always for high temporalresolution

UNIS 2011-11-15 – p. 64

Slow: ≈ 42 photons/pixel

0.1

1

10

100

1 10 100 1000

SN

R

photons/pixel (assuming 90% QE)

Slow readout EM ON vs. Conventional Ampl.

Ideal CCD201-201 MHz Con. CCD201-20

EM ON 1 MHz CCD201-20

UNIS 2011-11-15 – p. 65

Not always for low temporalresolution

UNIS 2011-11-15 – p. 66

Intercalibration

UNIS 2011-11-15 – p. 67

IntercalibrationThis is the process of intercalibrating calibrationsources and to transfer absolute calibrationinformation between different instruments andresearch groups.

Hans Lauches intercalibration photometer (responsibleperson: 1981–1999 Lauche, 1999-2011 Widell, SSC,

2011– Brändström, IRF)UNIS 2011-11-15 – p. 68

The European Rayleigh

UNIS 2011-11-15 – p. 69

Intercal. procedure• Calibrators are compared at calibration

workshops using a calibration-photometerwith 7 filters and a reference source.

UNIS 2011-11-15 – p. 70



• Last known absolute callibration of thecalibration equipment against a nationalstandard (NBS) was done by [Torr and Espy,1981].

UNIS 2011-11-15 – p. 70



• Last known absolute callibration of thecalibration equipment against a nationalstandard (NBS) was done by [Torr and Espy,1981].

• Known calibration workshops at the opticalmeetings were: Aberdeen 1981, Lindau 1983,Lysebu 1985, Saskatoon 1987, Lindau 1989,Wien 1991, Lindau 1999, Stockholm 2000,Oulu 2001, Kiruna 2006, Andøya 2007 andSodankylä 2011.

UNIS 2011-11-15 – p. 70

Intercal. workshops

0

5

10

15

20

25

1980 1985 1990 1995 2000 2005 2010

Number of participating calibrationsources in intercalibration workshops 1981-2011

UNIS 2011-11-15 – p. 71

Sodankylä 2011

UNIS 2011-11-15 – p. 72

and the FMI-sphere

UNIS 2011-11-15 – p. 73

To be done here

After Sigernes et al. [2008]

UNIS 2011-11-15 – p. 74

Intercal. results

0.001

0.01

0.1

1

10

100

1000

3500 4000 4500 5000 5500 6000 6500 7000 7500

[Ray

leig

hs/A

ngst

rom

]

Wavelength [Angstrom]

Y275L1614920B

UNIS 2011-11-15 – p. 75

Intercal. errors

-30

-20

-10

0

10

20

30

4000 4500 5000 5500 6000 6500 7000

ratio

[%]

Wavelength [Angstrom]

Confusogram of calibration ratios [1985,1999,2000,2001 to 2006]

y275 1985y275 1999y275 2000y275 2001

l1614 1985l1614 1999l1614 2000l1614 2001920b 1985920b 1999920b 2000920b 2001

UNIS 2011-11-15 – p. 76

Calibration issues

UNIS 2011-11-15 – p. 77

CalibrationCalibration is the process of answering thefollowing two basic questions:

1. What physical value does the pixel represent?(absolute calibration)

2. How is each pixel mapped to the observedobject? (geometrical calibration)

UNIS 2011-11-15 – p. 78

Abs. calibration (ALIS)

UNIS 2011-11-15 – p. 79

ChallengeRead the “28. Appendix” and compare toSigernes et al. [2008]. You might also want tocompare to Torr and Espy [1981]Calculate R/Å for the IRF-UJO-Y275 radioactivesource around 5577 Å using the result in “28.Appendix” and compare to latest intercalibrationresult from Sodankylä. (That source is marked15 µlm

UNIS 2011-11-15 – p. 80

ALIS

UNIS 2011-11-15 – p. 81

ALIS 2009–2012

T

KO

A

I

Y

F

B

E

DS

R

N

M

Sweden

Finland

Norway

UNIS 2011-11-15 – p. 82

Spectroscopic imaging

4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 9000Wavelength [Å]

UNIS 2011-11-15 – p. 83

Selectable common volumes

−200 −100 0 100 200−150

−100

−50

0

50

100

MerasjaerviSilkimuotka

Tjautjas

surveilance

KirunaNikaluokta

Abisko

−100 0 100 200−150

−100

−50

0

50

Merasjaervi

Silkimuotka

Tjautjas

mag_zen

KirunaNikaluokta

Abisko

−200 −100 0 100 200

−200

−150

−100

−50

0

50


TjautjasKiruna

south

Nikaluokta

Abisko

−200 −100 0 100

−100

−50

0

50

100

Merasjaervi

Silkimuotka

Tjautjas

Kiruna

core

Nikaluokta

Abisko

−400 −200 0 200 400

0

100

200

300

400


TjautjasKiruna

east−west

NikaluoktaAbisko

−300 −200 −100 0 100 200

0

100

200

300


TjautjasKirunaNikaluokta

Abisko

north

−200 0 200

0

100

200

300

400


TjautjasKiruna

eiscat

NikaluoktaAbisko

Approximate field of view at 110 km

−200 0 200

0

100

200

300

400


TjautjasKiruna

heating

NikaluoktaAbisko

o50 90o

[km]0−50 100−100 200−150

0

50

100

150

200

250

[km]

aφ

Azimuth

W E

S

α

x

Ny

zβ β

UNIS 2011-11-15 – p. 84

Scientific results and capabilities

UNIS 2011-11-15 – p. 85

Auroral tomography

−50 0 5090

100

110

120

130

140

150

160

20:09:00A

ltitu

de (

km)

−50 0 5090

100

110

120

130

140

150

160

20:09:30

−50 0 5090

100

110

120

130

140

150

160

20:10:00

Alti

tude

(km

)

−50 0 5090

100

110

120

130

140

150

160

20:10:30

−50 0 5090

100

110

120

130

140

150

160

20:11:00

Alti

tude

(km

)

North (km)−50 0 50

90

100

110

120

130

140

150

160

20:11:30

North (km)

40 km west of Kiruna

−50 0 5090

100

110

120

130

140

150

160

20:09:00

Alti

tude

(km

)

−50 0 5090

100

110

120

130

140

150

160

20:09:30

−50 0 5090

100

110

120

130

140

150

160

20:10:00

Alti

tude

(km

)

−50 0 5090

100

110

120

130

140

150

160

20:10:30

−50 0 5090

100

110

120

130

140

150

160

20:11:00

Alti

tude

(km

)

North (km)−50 0 50

90

100

110

120

130

140

150

160

20:11:30

North (km)

70 km west of Kiruna

1997-02-16 ALIS/FAST/EISCAT

UNIS 2011-11-15 – p. 86

UNIS 2011-11-15 – p. 87

UNIS 2011-11-15 – p. 88

Auroral electron spectras,

from tomography,

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

200 400 600 800 1000 1200

100

101

102

time after 23:20:00 UT (s)

elec

tron

ene

rgy

log10

electron energy flux

UNIS 2011-11-15 – p. 89

Auroral electron spectras,

from tomography,

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

200 400 600 800 1000 1200

100

101

102


elec

tron

ene

rgy

log10

electron energy flux

and from spectroscopicratios (right panel).

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 500 1000

−60

−40

−20

0

20

40

60

80


N−

S d

ista

nce

Characteristic energy (keV)

0.15

0.2

0.25

0.3

0.35

0 500 1000

−60

−40

−20

0

20

40

60

80


N−

S d

ista

nce

Oxygen scaling factor

40

60

80

100

120

140

160

0 500 1000

−50

0

50


N−

S d

ista

nce

4278 A

30

40

50

60

70

80

90

100

110

0 500 1000

−50

0

50


N−

S d

ista

nce

8446 A

50

100

150

200

250

0 500 1000

−50

0

50


N−

S d

ista

nce

6300 A

After Gustavsson et al. [2001b], Phys. Chem. Earth 26.

UNIS 2011-11-15 – p. 89

UNIS 2011-11-15 – p. 90

filter/expose sequence

0 2 4 6 8 10 12 14 16 18 20

Bus

Kiruna

Optlab

Abisko

time (s)

Filter/exposure sequence: sync−rapid−aeronomi

UNIS 2011-11-15 – p. 91

UNIS 2011-11-15 – p. 92

UNIS 2011-11-15 – p. 93

UNIS 2011-11-15 – p. 94

Daylight aurora

After Rees et al. [2000], GRL, 27.

UNIS 2011-11-15 – p. 95

Radio-induced optical emissions

UNIS 2011-11-15 – p. 96

RIOEALIS made the first unambigous observation of

high-latitude RIOE 1999-02-1617:40:15 17:40:35 17:40:55 17:41:15 17:41:35 17:41:55

0

1000

2000

3000

4000

17:43:55 17:44:05 17:44:15 17:44:25 17:44:35 17:44:45

0

1000

2000

3000

4000

After [Brandstrom et al., 1999], GRL, 26.

UNIS 2011-11-15 – p. 97

Tomography of RIOE

After Gustavsson et al. [2001a], JGR

106, 29

ALIS made the first tomo-graphic estimate of volumedistribution of RIOE.

UNIS 2011-11-15 – p. 98

UNIS 2011-11-15 – p. 99

UNIS 2011-11-15 – p. 100

Meteor research

UNIS 2011-11-15 – p. 101

A strange meteor trail

130

120

110

100

95

1

2

3

4

5

6

7

8

9

10

x 104

95

100

110

2000

2500

3000

3500

4000

4500

5000

4227 Å (left) 5893 Å (right)After Pellinen-Wannberg et al. [2004, GRL 31], GRL 31.

UNIS 2011-11-15 – p. 102

Polar-Stratospheric clouds

−20 −10 0

40

50

60

70

Triangulation

212223

24

25

26

After Enell [2002], IRF Sci. Rep. 278

UNIS 2011-11-15 – p. 103

Future plans and challenges

UNIS 2011-11-15 – p. 104

Small structureThe aurora is extremly rich in small structure

“With respect to understanding thedynamic coupling between themagnetosphere and the auroralionosphere the observational bias towardbright aurora is physically unjustified”[Semeter 2001]

UNIS 2011-11-15 – p. 105

We do not understand:• Creation of narrow arcs

UNIS 2011-11-15 – p. 106

We do not understand:• Creation of narrow arcs• Diffuse aurora

UNIS 2011-11-15 – p. 106

We do not understand:• Creation of narrow arcs• Diffuse aurora• Pulsating aurora

UNIS 2011-11-15 – p. 106

We do not understand:• Creation of narrow arcs• Diffuse aurora• Pulsating aurora• The role of the ionosphere in the

magnetosphere-ionosphere coupling

UNIS 2011-11-15 – p. 106


magnetosphere-ionosphere coupling• How are different scales related to each

other?

UNIS 2011-11-15 – p. 106


magnetosphere-ionosphere coupling• How are different scales related to each

other?

Thus we need instruments measuring differentscales with high temporal and spatial resolution,e.g. Polar/VIS, ASC, ALIS, ASK

UNIS 2011-11-15 – p. 106

ALIS 2010–2014• Electrodynamics of auroral structures: get

most out of EISCAT-UHF• ALIS/EISCAT/REIMEI• Improve temporal resolution: EMCCD• Review which sites to use• Ionospheric sounding rockets?• Collaboration for development of methods

and models• Calibration!!!• Improve access to data

UNIS 2011-11-15 – p. 107

In particularwe will work to answer the following specificquestions:

1. What is the temporal and spatial scaledistribution of small (less than a few km)auroral structures?.

2. What are the temporal and spatial variationsof the primary particle distributions causingsmall auroral structures?

3. What is the detailed 3D electrodynamics ofsmall auroral structures?

4. How does ionospheric feedback influenceauroral structure?

UNIS 2011-11-15 – p. 108

and now. . .

UNIS 2011-11-15 – p. 109

My brain hurts!

Mr. T. F. Gumby:—Doctor! Doctor! DOCTOR! DOCTOR! Doctor!

— Are you the brain specialist? — My brain hurts!

http://www.mwscomp.com/mpfc/gumbrain.htmlUNIS 2011-11-15 – p. 110

http://www.mwscomp.com/mpfc/gumbrain.html

It’s

The end!

UNIS 2011-11-15 – p. 111

THE END!

UNIS 2011-11-15 – p. 112

The end?

Kiruna ASC 2007-02-05 17.39.00 UTC 10s exp.UNIS 2011-11-15 – p. 113

References

References

Baker, D. J., Rayleigh, the unit for light radiance, Applied Op-

tics, 13, 2160–2163, 1974.

Baker, D. J., and G. J. Romick, The Rayleigh interpretation of

the unit in terms of column emission rate or apparent radi-

ance expressed in SI units, Applied Optics, 15, 1966–1968,

1976.

Brandstrom, B. U. E., T. B. Leyser, A. Steen, M. T. Rietveld,

B. Gustavsson, T. Aso, and M. Ejiri, Unambigous evidence of

HF pump-enhanced airglow, Geophys. Res. Lett., 26, 3561–

3564, 1999.

Brandstrom, U., The Auroral Large Imaging System — Design,

operation and scientific results, Ph.D. thesis, Swedish Insti-

tute of Space Physics, Kiruna, Sweden, 2003, (IRF Scientific

Report 279), ISBN: 91-7305-405-4.

Chamberlain, J. W., Physics of the aurora and airglow , Classics

in geophysics, AGU (American Geophysical Union), 1995, (A

reprint of the original work from 1961).

113-1

Enell, C.-F., Optical studies of polar stratospheric clouds and

related phenomena, Ph.D. thesis, Swedish Institute of Space

Physics, Kiruna, Sweden, 2002, (IRF Scientific Report 278),

ISBN: 91-7305-307-4.

Gustavsson, B., T. Sergienko, M. T. Rietveld, F. Honary,

A. Steen, B. U. E. Brandstrom, T. B. Leyser, A. L. Aruliah,

T. Aso, and M. Ejiri, First tomographic estimate of volume dis-

tribution of enhanced airglow emission caused by HF pump-

ing, J. Geophys. Res., 106, 29,105–29,123, 2001a.

Gustavsson, B., A. Steen, T. Sergienko, and B. U. E. Brand-

strom, Estimate of auroral electron spectra, the power

of ground-based multi-station optical measurements, Phys.

Chem. Earth, 26, 189–194, 2001b.

Holst, G. C., CCD arrays, cameras and displays, second

ed., The International Society for Optical Engineering, 1998,

ISBN: 0-8194-2853-1.

Hunten, D. M., F. E. Roach, and J. W. Chamberlain, A photo-

metric unit for the aurora and airglow, J. Atmos. Terr. Phys.,

8, 345–346, 1956.

Janesick, J. R., T. Elliott, S. Collins, M. M. Blouke, and J. Free-

man, Scientific charge-coupled devices, Optical Engineering,

26, 692–714, 1987.

113-2

Pellinen-Wannberg, A., E. Murad, B. Gustavsson, U. Brand-

strom, C.-F. Enell, C. Roth, I. P. Williams, and A. Steen, Op-

tical observations of water in Leonid meteor trails, Geophys.

Res. Lett., 31, 2004.

Rees, D., M. Conde, A. Steen, and U. Brandstrom, The first

daytime ground-based optical image of the aurora, Geophys.

Res. Lett., 27 , 313–316, 2000.

Sigernes, F., J. M. Holmes, M. Dyrland, D. A. Lorentzen,

T. Svenøe, K. Heia, T. Aso, S. Chernouss, and C. S. Deehr,

Sensitivity calibration of digital colour cameras for auroral

imaging, Optics Express, 16, 15,623–15,632, 2008.

Torr, M. R., and P. Espy, Intercalibration of instrumentation

used in the observation of atmospheric emissions: Second

progress report, Tech. Rep. 101, Utah State University, Cen-

ter for atmospheric and space sciences, Logan Utah, 1981.

Wolfe, W. L., Introduction to Radiometry , vol. TT29, The Inter-

national Society for Optical Engineering, 1998.

113-3

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