天文観測の観点からの「夜間の発光」についてのレビュー …step0ku.kugi.kyoto-u.ac.jp/~akiya/prefiles/20130716.pdf · 1 Max–Planck–Institut f¨ur Astronomie,

天文観測の観点からの「夜間の発光」についてのレビュー

(Review on “Diffuse night sky brightness”)

2013/7/16 MPEWG秋谷　祐亮

「光」を利用する観測• イメージング観測；「見たまま」の様子を記録する→対象領域の形状や大きさを調べる

• 分光観測；波長域を選ぶことで、対象領域の温度や組成を調べる

• きっちりと分けられるものでもなく、2つが混ざったような観測もある。

• どちらにしても、観測したい「光」以外にも（場合によっては邪魔な）いろいろな光が存在している。

夜空には発光源がいろいろある

• 旧約聖書の創世記1章3節はともかく、Maxwellの式から電磁波の伝搬が導かれる。

• 大気光観測を行う際に、大気光発光以外の光を考慮する必要がある。また、ソースからの「光」は必ずしも可視域には限らない。

• 参考レビュー論文：Ch. Leinert et al. “The 1997 reference of diffuse night sky brightness” (Astronomy & Astrophysics Supplement Series 127, 1-99 (1998))

I =! +!

"!P (s)ds (1)

(z + r)2 = s2 + (ztg + r)2 (2)

I = 2! +!

ztg

z"

z2 " ztg2P (z)dz (3)

!ni

!t= "!"i

!z+ Pi " Li "

!(niw)

!z(4)

"i = "(Di + K)#!ni

!z+

!ni

!T

!T

!z

$

"#Di

Hi+

K

H

$

ni (5)

K(z) =A

"n(z)

[cm2 s"1] (6)

神は言った。

# · B = 0

#$ E = "!B

!t# · D = #

#$ H = j +!D

!t

そして光があった。

1

夜空には発光源がいろいろある• 大気光観測を行う際に、大気光発光以外の光を考慮する必要がある。また、ソースからの「光」は必ずしも可視域には限らない。

• 参考レビュー論文：Ch. Leinert et al. “The 1997 reference of diffuse night sky brightness” (Astronomy & Astrophysics Supplement Series 127, 1-99 (1998))

ASTRONOMY & ASTROPHYSICS JANUARY I 1998, PAGE 1

SUPPLEMENT SERIES

Astron. Astrophys. Suppl. Ser. 127, 1-99 (1998)

The 1997 reference of di↵use night sky brightness?

Ch. Leinert1, S. Bowyer2, L.K. Haikala3, M.S. Hanner4, M.G. Hauser5, A.-Ch. Levasseur-Regourd6,I. Mann7, K. Mattila3, W.T. Reach8, W. Schlosser9, H.J. Staude1, G.N. Toller10, J.L. Weiland11,J.L. Weinberg12, and A.N. Witt13

1 Max–Planck–Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg, Germany2 Astronomy Dept., University of California, 601 Campbell Hall, Berkeley CA 94720, U.S.A.3 Observatory, P.O. Box 14, FIN-00014 University of Helsinki, Finland4 Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena CA 91109, U.S.A.5 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218, U.S.A.6 Service d’Aeronomie, BP. 3, F-91371 Verrieres le Buisson, France7 Max–Planck–Institut fur Aeronomie, Max-Planck-Straße 2, D-37191 Katlenburg-Lindau, Germany8 Institut d’Astrophysique Spatiale, Universite Paris XI, 91405 Orsay Cedex, France9 Astronomisches Institut, Ruhr-Universitat Bochum, D-44780 Bochum, Germany10 General Sciences Corporation, 6100 Chevy Chase Drive, Laurel, MD 20707, U.S.A.11 Hughes STX, NASA/Goddard Space Flight Center Code 685.9, Greenbelt, MD 20771, U.S.A.12 MK Industries, 2137E Flintstone Drive, Tucker, Georgia 30084, U.S.A.13 Ritter Astrophys. Res. Center, University of Toledo, Toledo, OH 43606, U.S.A.

Received August 7; accepted September 8, 1997

Abstract. In the following we present material in tabu-lar and graphical form, with the aim to allow the non-specialist to obtain a realistic estimate of the di↵use nightsky brightness over a wide range of wavelengths from thefar UV longward of Ly↵ to the far-infrared. At the sametime the data are to provide a reference for cases in whichbackground brightness has to be discussed, including theplanning for space observations and the issue of protectionof observatory sites. We try to give a critical presentationof the status at the beginning of 1997.

Key words: di↵use radiation — interplanetarymedium — atmospheric e↵ects — astronomical dabases:miscellaneous — infrared: general — ultraviolet: general

Contents

1. Overview2. Brightness units3. Coordinate transformations4. Total sky brightness5. Tropospheric scattering6. Airglow6.1 Airglow spectrum, UV to IR6.2 Dependence on zenith distance6.3 Variations

Send o↵print requests to: Ch. Leinert? Prepared by members of Commission 21 “Light of the nightsky” of the IAU, including most of the recent (vice-)presidents.

6.4 Geocorona6.5 Interplanetary emissions6.6 Shuttle glow

7. Light pollution8. Zodiacal light8.1 Overview and general remarks8.2 Heliocentric dependence8.3 Zodiacal light at 1 AU in the visual8.4 Wavelength dependence and colour8.5 Zodiacal light in the infrared8.6 Zodiacal light in the ultraviolet8.7 Seasonal variations8.8 Structures in the zodiacal light8.9 The zodiacal light seen from other places

9. Coronal brightness and polarisation10. Integrated starlight10.1 Model predictions based on star counts10.2 Ultraviolet10.3 Ground-based UBVR photometry10.4 Pioneer 10/11 spaceborne visual photometry10.5 Near-and mid-infrared

11. Di↵use galactic light11.1 Overview11.2 Visual11.3 Near-infrared11.4 Thermal infrared11.5 Ultraviolet

12. Extragalactic background light

夜空には発光源がいろいろある

ASTRONOMY & ASTROPHYSICS JANUARY I 1998, PAGE 1

SUPPLEMENT SERIES

Astron. Astrophys. Suppl. Ser. 127, 1-99 (1998)

The 1997 reference of di↵use night sky brightness?

Ch. Leinert1, S. Bowyer2, L.K. Haikala3, M.S. Hanner4, M.G. Hauser5, A.-Ch. Levasseur-Regourd6,I. Mann7, K. Mattila3, W.T. Reach8, W. Schlosser9, H.J. Staude1, G.N. Toller10, J.L. Weiland11,J.L. Weinberg12, and A.N. Witt13

1 Max–Planck–Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg, Germany2 Astronomy Dept., University of California, 601 Campbell Hall, Berkeley CA 94720, U.S.A.3 Observatory, P.O. Box 14, FIN-00014 University of Helsinki, Finland4 Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena CA 91109, U.S.A.5 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218, U.S.A.6 Service d’Aeronomie, BP. 3, F-91371 Verrieres le Buisson, France7 Max–Planck–Institut fur Aeronomie, Max-Planck-Straße 2, D-37191 Katlenburg-Lindau, Germany8 Institut d’Astrophysique Spatiale, Universite Paris XI, 91405 Orsay Cedex, France9 Astronomisches Institut, Ruhr-Universitat Bochum, D-44780 Bochum, Germany10 General Sciences Corporation, 6100 Chevy Chase Drive, Laurel, MD 20707, U.S.A.11 Hughes STX, NASA/Goddard Space Flight Center Code 685.9, Greenbelt, MD 20771, U.S.A.12 MK Industries, 2137E Flintstone Drive, Tucker, Georgia 30084, U.S.A.13 Ritter Astrophys. Res. Center, University of Toledo, Toledo, OH 43606, U.S.A.

Received August 7; accepted September 8, 1997

Abstract. In the following we present material in tabu-lar and graphical form, with the aim to allow the non-specialist to obtain a realistic estimate of the di↵use nightsky brightness over a wide range of wavelengths from thefar UV longward of Ly↵ to the far-infrared. At the sametime the data are to provide a reference for cases in whichbackground brightness has to be discussed, including theplanning for space observations and the issue of protectionof observatory sites. We try to give a critical presentationof the status at the beginning of 1997.

Key words: di↵use radiation — interplanetarymedium — atmospheric e↵ects — astronomical dabases:miscellaneous — infrared: general — ultraviolet: general

Contents

1. Overview2. Brightness units3. Coordinate transformations4. Total sky brightness5. Tropospheric scattering6. Airglow6.1 Airglow spectrum, UV to IR6.2 Dependence on zenith distance6.3 Variations

Send o↵print requests to: Ch. Leinert? Prepared by members of Commission 21 “Light of the nightsky” of the IAU, including most of the recent (vice-)presidents.

6.4 Geocorona6.5 Interplanetary emissions6.6 Shuttle glow

7. Light pollution8. Zodiacal light8.1 Overview and general remarks8.2 Heliocentric dependence8.3 Zodiacal light at 1 AU in the visual8.4 Wavelength dependence and colour8.5 Zodiacal light in the infrared8.6 Zodiacal light in the ultraviolet8.7 Seasonal variations8.8 Structures in the zodiacal light8.9 The zodiacal light seen from other places

9. Coronal brightness and polarisation10. Integrated starlight10.1 Model predictions based on star counts10.2 Ultraviolet10.3 Ground-based UBVR photometry10.4 Pioneer 10/11 spaceborne visual photometry10.5 Near-and mid-infrared

11. Di↵use galactic light11.1 Overview11.2 Visual11.3 Near-infrared11.4 Thermal infrared11.5 Ultraviolet

12. Extragalactic background light

さまざまな発光源2 C h. L einer t et al.: T he 1997 reference of di� use night sk y bright ness

0.1 1 10 100 1000 10000Wavelength ( µm )

10-10

10-9

10-8

10-7

10-6

10-5

10-4

Brig

htne

ss ν

l ν (

W m

-2 sr

-1 )

CMB (2.726K)

Zodiacal light

Faint stars

Cirrus

OH

AirglowLyα

OΙO2

Fig. 1. O v erv iew on t he bright ness of t he sk y ou tside t he low er t errest rial a tm osp here and a t high eclip t ic and galact ic la t i t udes.T he z odiacal em ission and sca t t ering as w ell as t he int egra t ed light of st ars are giv en for t he S ou t h E clip t ic P ole ( l = 27 6� ,b = �3 0 � ) . T he bright m agni t ude cu t - o� for t he st ellar com p onent is V = 6.0 m ag for 0 .3 – 1 µm . I n t he infrared, st ars bright ert han 15 J y b etw een 1.25 and 4 .8 5 µm and bright er t han 8 5 J y a t 12 µm are ex cluded. N o cu t - o� w as ap p lied to t he U V da t a,� 0 .3 µm . T he int erst ellar cirrus com p onent is norm aliz ed for a colum n densi t y of 10 20 H - a tom s cm �2 corresp onding to av isual ex t inct ion of 0 .0 5 3 m ag. T his is close to t he v alues a t t he darkest p a t ches in t he sk y. S ource for t he long- w av elengt hda t a, � � 1.25 µm , are C O B E D I R B E and F I R A S m easurem ents as p resent ed by D eser t et al. ( 199 6) . T he I R cirrus sp ect rumis according to t he m odel of D eser t et al. ( 1990 ) fi t t ed to I R A S p hotom et ry. T he shor t - w av elengt h da t a, � 1.0 µm , are fromt he follow ing sources: z odiacal light: L einer t & G run ( 1990 ) ; int egra t ed st arlight: � 0 .3 µm , G ondhalekar ( 1990 ) , � � 0 .3 µm ,M a t t ila ( 198 0 ) ; cirrus: � = 0 .15 µm , H aikala et al. ( 1995 ) , � = 0 .3 5 � 0 .75 µm , M a t t ila & S chnur ( 1990 ) , M a t t ila ( 1979) . T hegeocoronal L ym an ↵( 121. 6nm ) and t he O I ( 13 0 .4 , 13 5 . 6nm ) line int ensi t ies w ere as m easured w i t h t he F aint O b j ect C am eraof t he H ubble S p ace Telescop e a t a height of 610 km ( C aulet et al. 1994 ) . T he v arious references for t he airglow em ission canb e found in S ec t . 6

1. Overview

This paper is concerned with the night sky brightness fromthe far UV (⇡ 100 nm) to the far infrared (⇡ 200 µm).

Quite a few sources contribute to the di↵use brightnessof the moonless sky (Inight sky) in this wavelength range:–airglow from the upper atmosphere (IA).–Zodiacal light, both as scattered sunlight and thermalemission of interplanetary dust particles, from interplane-tary space (IZL). (In the far UV interplanetary Ly↵ emis-sion is important.)–Integrated starlight (IISL) of the stars not individually ac-counted for–di↵use galactic light (IDGL), in the UV and visual mainlyreflections o↵ interstellar dust particles. Their infraredthermal emission is known as “cirrus” since the pioneer-ing IRAS observations. It dominates the sky brightness inthe far-infrared. Interstellar gas contributes line emissions

over all of our wavelength range.–Extragalactic background light (IEBL) in addition to theradiation of individually detected galaxies.The combined light of these radiations is attenuated

by atmospheric extinction, while tropospheric scatteringof the infalling flux adds a non-negligible brightness com-ponent (Isca).Formally, the above statements may be expressed as

Inight sky

= ( IA

+ IZL

+ IISL

+ IDGL

+ IEBL

) · e�⌧ + Isca

. ( 1)

It should be noted that the “extinction coe�cient” ⌧(which depends on wavelength �, zenith distance z, heightof the observer and change of the atmospheric condi-tions with time) for di↵use sources has a value di↵erentfrom that determined for stars. The scattered light Iscanot only contains additional contributions due to starsand galaxies otherwise accounted for individually, but,

• 夜空の明るさ＝大気光＋黄道光＋星明かり＋散乱銀河光＋銀河外からの光

• 大気による吸収や対流圏での散乱も無視できない

輝度の単位• 慣用的定義• S10単位；A0星基準、太陽基準• 物理的定義• photons / cm2 s sr nm• Rayleigh / nm = 106 / 4π photons cm2 s sr nm 【測光学的定義（正式）：1R = 106 / 4π photons cm2 s sr】

• W / m2 sr μm （流束）

全天の明るさ（１）• 遠紫外域(91.2 nm - 180 nm)：主に星明かりと星間塵による散乱

• Lyα(121.6 nm)の強い放射；中性水素による太陽放射の散乱

• Geocoronaの流束は3kR（夜間）から34kR（昼間）まで10倍近く変動する

• 近紫外域(180 nm - 300 nm)：黄道光、星明かり、星間塵による散乱

• 可視光域：大気光、黄道光、対流圏での散乱

• 波長ごとに観測される強度は異なる（右上）

• 太陽活動の活発さに応じて大気光の発光強度は変動する（右下）

14 Ch. Leinert et al.: The 1997 reference of di↵use night sky brightness

band and broad-band observations. The central wave-lengths of the intermediate bands have been selected tocoincide with minima of the night sky spectrum. Figure9 indicates what emission may be expected outside thosebands. Brightness variations usually are well correlatedbetween di↵erent wavelength bands (see Leinert et al. 1995and Fig. 28 in Sect. 6.3). An example for the variation ofsky brightness with solar activity is given in Fig. 10.

Fig. 9. A low resolution night sky spectrum at PalomarObservatory, taken on November 28, 1972 (Turnrose 1974),compared to medium band measurements on Calar Alto (CA)

Fig. 10. Correlation between the night sky brightness observedat Calar Alto at 525 nm with the solar activity, measured bythe 10.7 cm radio flux density (in units of 104 Jy)

4.3. Near-infrared from the ground

The near-infrared sky brightness seen from ground at atypical observing site is shown in Fig. 11. Below 2 µm thenight sky emission is dominated by OH airglow emission(see also Sect. 6). Above 2 µm thermal emission by theatmosphere is dominating. Between 2 µm and 4 µm emis-sion from the telescope also adds a considerable fractionto the total radiation.The situation is quite di↵erent for observations from

Antarctica. The much reduced thermal emission in an en-vironment with winter temperatures below �60 �C leadsto a substantial reduction of sky background particularlyin the K photometric band (Ashley et al. 1996; Nguyenet al. 1996, see Fig. 12 and Table 5). Because of the ab-sence of strong airglow emission between 2.3 µm and2.5 µm (see Fig. 27, Sect. 6.1.c), in this spectral regionvalues of zenith sky brightness as low as 50 µJy arcsec�2

(K = 17.7 mag arcsec�2) have been measured. The de-pendence on zenith distance is normal: proportional tosec z down to z ⇡ 50�. In the L band, between 2.9 µmand 4.1 µm, still an improvement by a factor of 40 � 20was found (Ashley et al. 1996).

Table 5. Comparison of K band sky brightnessesa

� �� I⌫ I

Site (µm) (µm) (µJy/200) (mag/200) Ref.Mauna Kea 2.22 0.39 ⇡4000 ⇡13 1Mauna Kea 2.11 0.35 ⇡2700 ⇡13.4 1Balloon 2.4 0.1 < 26 < 18.4 2Balloon 2.38 0.08 130±19 16.7 3South Pole 2.36 0.14 162±67 16.5 4South Pole 2.40 0.04 50 17.7 5a adapted from Nguyen et al. (1996).

References: 1Wainscoat & Cowie (1992), 2Hofmann et al.(1974), 3Matsumoto et al. (1994), 4Nguyen et al. (1996),5Ashley et al. (1996).

4.4. Infrared

Table 6 shows the darkest spots on the sky from 1 µm to240 µm as measured by the infrared photometric experi-ment DIRBE on the COBE satellite in an 0.7�⇥0.7� widefield-of-view (adapted from Hauser 1996). These are con-servative upper limits to the cosmic infrared backgroundlight. For wavelengths of � 60 µm, where the zodia-cal light (thermal emission) dominates, the darkest fieldsare close to the ecliptic poles. For longer wavelengths, thethermal emission of interstellar dust is dominating, andthe darkest fields are found in regions around the galacticpoles with particularly low HI 21 cm emission (Lockmanet al. 1986).


band and broad-band observations. The central wave-lengths of the intermediate bands have been selected tocoincide with minima of the night sky spectrum. Figure9 indicates what emission may be expected outside thosebands. Brightness variations usually are well correlatedbetween di↵erent wavelength bands (see Leinert et al. 1995and Fig. 28 in Sect. 6.3). An example for the variation ofsky brightness with solar activity is given in Fig. 10.

Fig. 9. A low resolution night sky spectrum at PalomarObservatory, taken on November 28, 1972 (Turnrose 1974),compared to medium band measurements on Calar Alto (CA)

Fig. 10. Correlation between the night sky brightness observedat Calar Alto at 525 nm with the solar activity, measured bythe 10.7 cm radio flux density (in units of 104 Jy)

4.3. Near-infrared from the ground

The near-infrared sky brightness seen from ground at atypical observing site is shown in Fig. 11. Below 2 µm thenight sky emission is dominated by OH airglow emission(see also Sect. 6). Above 2 µm thermal emission by theatmosphere is dominating. Between 2 µm and 4 µm emis-sion from the telescope also adds a considerable fractionto the total radiation.The situation is quite di↵erent for observations from

Antarctica. The much reduced thermal emission in an en-vironment with winter temperatures below �60 �C leadsto a substantial reduction of sky background particularlyin the K photometric band (Ashley et al. 1996; Nguyenet al. 1996, see Fig. 12 and Table 5). Because of the ab-sence of strong airglow emission between 2.3 µm and2.5 µm (see Fig. 27, Sect. 6.1.c), in this spectral regionvalues of zenith sky brightness as low as 50 µJy arcsec�2

(K = 17.7 mag arcsec�2) have been measured. The de-pendence on zenith distance is normal: proportional tosec z down to z ⇡ 50�. In the L band, between 2.9 µmand 4.1 µm, still an improvement by a factor of 40 � 20was found (Ashley et al. 1996).

Table 5. Comparison of K band sky brightnessesa

� �� I⌫ I

Site (µm) (µm) (µJy/200) (mag/200) Ref.Mauna Kea 2.22 0.39 ⇡4000 ⇡13 1Mauna Kea 2.11 0.35 ⇡2700 ⇡13.4 1Balloon 2.4 0.1 < 26 < 18.4 2Balloon 2.38 0.08 130±19 16.7 3South Pole 2.36 0.14 162±67 16.5 4South Pole 2.40 0.04 50 17.7 5a adapted from Nguyen et al. (1996).

References: 1Wainscoat & Cowie (1992), 2Hofmann et al.(1974), 3Matsumoto et al. (1994), 4Nguyen et al. (1996),5Ashley et al. (1996).

4.4. Infrared

Table 6 shows the darkest spots on the sky from 1 µm to240 µm as measured by the infrared photometric experi-ment DIRBE on the COBE satellite in an 0.7�⇥0.7� widefield-of-view (adapted from Hauser 1996). These are con-servative upper limits to the cosmic infrared backgroundlight. For wavelengths of � 60 µm, where the zodia-cal light (thermal emission) dominates, the darkest fieldsare close to the ecliptic poles. For longer wavelengths, thethermal emission of interstellar dust is dominating, andthe darkest fields are found in regions around the galacticpoles with particularly low HI 21 cm emission (Lockmanet al. 1986).

全天の明るさ（２）• 近赤外領域

• 波長2μm以下の領域；OH大気光（さまざまなバンド）が支配的

• 波長2μm以上の領域；大気の熱放射が支配的

• 南極の冬は極端な低温のため波長2μm以上の領域で様子が変わってくる（右下）

• 赤外領域

• 波長60μm以下の領域；黄道光（熱放射）が支配的

• 波長60μm以上の領域；星間塵の熱放射が支配的

• 水素原子由来の波長21cmの電波が宇宙空間にたくさん

Ch. Leinert et al.: The 1997 reference of di↵use night sky brightness 15

Fig. 11. Near-infrared spectrum of the night sky brightness, measured just inside the cryostat window of the UKIRT IRCAMcamera (McCaughrean 1988). Note that 104 photons m�2 s�1 200�1µm�1 correspond to 4.23 Wm�2 sr�1µm�1. From Beckwith1994

Fig. 12. Near-infrared sky brightness around 2.3 µm as ob-served in Antarctica on May 31, 1994 with an ambient tem-perature of �62�. The dip around 2.4 µm is due to the lackof airglow emission in this region. The South Pole data arecompared to observations obtained at the Siding Spring ob-servatory (Australia) with an ambient temperature of +10�.From Ashley et al. (1996)

Table 6. Minimum observed sky brightnesses found in theDIRBE weekly averaged sky maps

� ⌫I⌫ = �I� I⌫ Reference(µm) (nW m�2 sr�1) (MJy/sr)1.25 393±13 0.16±0.005 12.2 150±5 0.11±0.004 13.5 63±3 0.074±0.004 14.9 192±7 0.31±0.01 112 2660±310 10.7±1.2 125 2160±330 18±3 160 261±22 5.2±0.4 1100 74±10 2.5±0.3 1140 57±6 2.7±0.3 1240 22±2 1.8±0.2 1

1Hauser (1996).


Fig. 11. Near-infrared spectrum of the night sky brightness, measured just inside the cryostat window of the UKIRT IRCAMcamera (McCaughrean 1988). Note that 104 photons m�2 s�1 200�1µm�1 correspond to 4.23 Wm�2 sr�1µm�1. From Beckwith1994

Fig. 12. Near-infrared sky brightness around 2.3 µm as ob-served in Antarctica on May 31, 1994 with an ambient tem-perature of �62�. The dip around 2.4 µm is due to the lackof airglow emission in this region. The South Pole data arecompared to observations obtained at the Siding Spring ob-servatory (Australia) with an ambient temperature of +10�.From Ashley et al. (1996)

Table 6. Minimum observed sky brightnesses found in theDIRBE weekly averaged sky maps

� ⌫I⌫ = �I� I⌫ Reference(µm) (nW m�2 sr�1) (MJy/sr)1.25 393±13 0.16±0.005 12.2 150±5 0.11±0.004 13.5 63±3 0.074±0.004 14.9 192±7 0.31±0.01 112 2660±310 10.7±1.2 125 2160±330 18±3 160 261±22 5.2±0.4 1100 74±10 2.5±0.3 1140 57±6 2.7±0.3 1240 22±2 1.8±0.2 1

1Hauser (1996).

対流圏による散乱効果• 大気光、黄道光、恒星からの光自体も対流圏による散乱の影響を受ける。黄道光は15%以上、恒星からの光については10 - 30%近い影響がある。

• 主にRayleigh散乱とMie散乱による。天の川や黄道光の観測を利用した観測がある[Staude, 1975]

• 一口に「対流圏の大気（あるいは空気）」と言っても、反射係数が水蒸気(1.33)とエアロゾル(1.5-0.1i)で異なるなど、単純な計算ではうまくいかない。

Rayleigh散乱とMie散乱の効果

• 散乱光の強度とpolarizationの大きさを、観測方向からの天頂距離の函数として表してある。

• 天頂角が小さいときにはMie散乱は無視できる。


5. Tropospheric scattering

From earthbound measurements of the night sky bright-ness the contribution due to tropospheric scattering (seeEq. (1)) has to be subtracted in order to determine its un-contaminated extraterrestrial intensity and polarization.The strongest contributions to scattered light come fromairglow, zodiacal light (ZL) and integrated starlight (ISL)- that is, the correction to be applied is in part determinedby the brightness distribution of the sources under studythemselves. The correction is of the order of 10� 100 S10,which corresponds to 15% or more of the Zodiacal light,and to typically 10 � 30% of the ISL. Due to the lim-ited accuracy to which the correction can be determined,it can be applied explicitly only to measurements aimedat the determination of ZL and ISL. The weaker compo-nents of the night sky brightness, DGL and EBL, must bedetermined by di↵erential methods.Detailed calculations on first order Rayleigh- and Mie-

scattering (including linear and circular polarization) inthe (spherical) Earth’s atmosphere illuminated by a uni-form, unpolarized source, by the Milky Way and by theZodiacal light were performed by Staude (1975) for vari-ous values of the optical thickness of the Rayleigh and Miecomponents of the atmosphere, and assuming two di↵erentvalues for the refractive index m of atmospheric aerosols(m = 1.33, as for water vapour, and m = 1.5� 0.1i, as foraerosols in dry air). The position and orientation of MilkyWay and Zodiacal Light cone were varied independentlyover the whole range occurring in practice. Some resultsfrom this study are reported in the following.

5.1. A uniform unpolarized source of unit brightness

The brightness of tropospherically scattered airglow canbe estimated using the results obtained for a uniform un-polarized source of unit brightness (extending over theentire visible sky) in the single scattering approximation,which are given in Figs. 13 and 14. They give the intensityof the scattered light and its polarization as a function ofzenith distance of the observing direction z0, for di↵erentvalues of the zenith extinction ⌧R of the Rayleigh and ⌧Mof the Mie component.

Table 7. The correction factors for multiple scattering in aRayleigh atmosphere for di↵erent values of the zenith extinc-tion ⌧

R

. See text for details

⌧R

FMS

fMS

0.05 1.12± 0.04 0.95 ± 0.050.10 1.22± 0.06 0.90 ± 0.050.15 1.33± 0.06 0.85 ± 0.050.20 1.44± 0.07 0.80 ± 0.05

S

Fig. 13. Intensity and polarization of the atmospheric scat-tered light in a pure Rayleigh atmosphere, for a source of unitbrightness and various values of the zenith extinction ⌧

R

, as afunction of zenith distance z

Fig. 14. Same as Fig. 13 for two pure Mie atmospheres


5. Tropospheric scattering

From earthbound measurements of the night sky bright-ness the contribution due to tropospheric scattering (seeEq. (1)) has to be subtracted in order to determine its un-contaminated extraterrestrial intensity and polarization.The strongest contributions to scattered light come fromairglow, zodiacal light (ZL) and integrated starlight (ISL)- that is, the correction to be applied is in part determinedby the brightness distribution of the sources under studythemselves. The correction is of the order of 10� 100 S10,which corresponds to 15% or more of the Zodiacal light,and to typically 10 � 30% of the ISL. Due to the lim-ited accuracy to which the correction can be determined,it can be applied explicitly only to measurements aimedat the determination of ZL and ISL. The weaker compo-nents of the night sky brightness, DGL and EBL, must bedetermined by di↵erential methods.Detailed calculations on first order Rayleigh- and Mie-

scattering (including linear and circular polarization) inthe (spherical) Earth’s atmosphere illuminated by a uni-form, unpolarized source, by the Milky Way and by theZodiacal light were performed by Staude (1975) for vari-ous values of the optical thickness of the Rayleigh and Miecomponents of the atmosphere, and assuming two di↵erentvalues for the refractive index m of atmospheric aerosols(m = 1.33, as for water vapour, and m = 1.5� 0.1i, as foraerosols in dry air). The position and orientation of MilkyWay and Zodiacal Light cone were varied independentlyover the whole range occurring in practice. Some resultsfrom this study are reported in the following.

5.1. A uniform unpolarized source of unit brightness

The brightness of tropospherically scattered airglow canbe estimated using the results obtained for a uniform un-polarized source of unit brightness (extending over theentire visible sky) in the single scattering approximation,which are given in Figs. 13 and 14. They give the intensityof the scattered light and its polarization as a function ofzenith distance of the observing direction z0, for di↵erentvalues of the zenith extinction ⌧R of the Rayleigh and ⌧Mof the Mie component.

Table 7. The correction factors for multiple scattering in aRayleigh atmosphere for di↵erent values of the zenith extinc-tion ⌧

R

. See text for details

⌧R

FMS

fMS

0.05 1.12± 0.04 0.95 ± 0.050.10 1.22± 0.06 0.90 ± 0.050.15 1.33± 0.06 0.85 ± 0.050.20 1.44± 0.07 0.80 ± 0.05

S

Fig. 13. Intensity and polarization of the atmospheric scat-tered light in a pure Rayleigh atmosphere, for a source of unitbrightness and various values of the zenith extinction ⌧

R

, as afunction of zenith distance z

Fig. 14. Same as Fig. 13 for two pure Mie atmospheres

黄道光の散乱

• 波長500 nmでの散乱の様子• Polarizationは太陽の方向と直角方向としている


S [ S

10 ]

Fig. 15. The intensity of the scattered integrated starlight asa function of zenith distance, for di↵erent azimuths and zenithextincion values of the Rayleigh resp. Mie components of theatmosphere. The galactic centre is assumed at the zenith, thegalactic equator crosses the horizon at A = 90�, 270�

S [ S

10 ]

Fig. 16. The intensity of the scattered zodiacal light for a pureRayleigh atmosphere with optical thickness ⌧

R

= 0.1. Positionof the sun at azimuth A� = 90�, zenith distance z� = 105�,the ecliptic is perpendicular to the horizon

S [ S

10 ]

Fig. 17. The intensity of the scattered zodiacal light for pureMie scattering with optical thickness ⌧

M

= 0.1, for particleswith refractive index m = 1.33. Otherwise same as for Fig. 16

Fig. 18. A typical height profile of airglow volume emission,as measured from the satellite OGO II. The peak near 90 kmis due to OH emission, the extended peak at higher altitudesto [OI] emission at 630 nm. From Reed & Blamont (1967)


S [ S

10 ]


S [ S

10 ]


R


S [ S

10 ]


M



大気光の発光源／高度

• 黄道光は大気光の2 - 3倍程度明るい（波長530nmで計測したとき）

• 天の川の明るさ：1 kR、満月の明るさ：1 MR

発光源波長発光層高度発光強度（天頂付近）He+ 30.4 nm > 1,000 kmO+ 83.4 nm > 1,000 kmLyβ 102.6 nm > 1,000 km ~ 10 RLyα 121.6 nm > 1,000 km 3kR (夜) - 34kR (昼)O 130.4 nm 250 - 300 km ~ 40 R (熱帯域)O 135.6 nm 250 - 300 km ~ 30 R (熱帯域)

O2 (Herzberg帯) 300 - 400 nm 90 km 8 R / nmN 519.9 nm 3 RO 557.7 nm 90 km 250 RNa 589 nm ~ 92 km 30 R (夏) - 100 R (冬)O 630.0 nm 250 - 300 km 60 RO 636.4 nm 250 - 300 km 20 RHα 656.3 nm > 1,000 km 4 - 6 R

擬連続光 400 - 700 nm 90 km 3 R / nmO2 864.5 nm ~ 80 km 1 kROH 600 - 4500 nm 85 km 4.5 MR (OH全体で)

発光層の高度分布

• 左：衛星「OGO Ⅱ」による観測[Reed et al., 1967]

• 高度90 km付近にOHによる発光層、さらに高層にはOからの630-nm発光層が見られている。

• 右：ロケットによる観測[Hecht et al., 2004]

• 実線が観測値を示している。


S [ S

10 ]


S [ S

10 ]


R


S [ S

10 ]


M



data and shown in Figure 7a. The agreement is quite goodabove 85 km except for the dip at 93 km.[26] Figure 9 shows a comparison between the derived

[O] profile from the O2A data and the four TIME-GCMmodel predictions. Clearly the peak is lower in altitude andmagnitude than the model predicts. One model run, thepreferred has a peak at about the right altitude but the shapeof the data above 85 km is different.

3.5. Atomic Oxygen Density Profiles From OHMand O2A

[27] In the region between 82 and 90 km whereequations (1b) and (1c) apply, the [O] obtained from O2Ais compared with that obtained from OHM as shown inFigure 10. The top panel of Figure 10 shows the O2A result(thin solid line) compared to the OHM result usingequation (1b) and either the Yee model (heavy solid line),the Turnbull and Lowe model (dashed line) or the Miesmodel (dotted line). While the qualitative shapes of all threeagree, the magnitudes are best given either by the Yee orTurnbull and Lowe models. The bottom panel of Figure 10uses the more exact equation (1c) where here the hydrogen

density is taken from TIME-GCM. Here the solid lineshows [O] data from O2A, the dashed line shows the [O]data from OHM using the Turnbull and Lowe model, thesolid line are the [O] data from OHM using the Yee model,and the heavy solid line shows the [O] data from OHMusing the Yee model with the [H] data multiplied by 2.[28] The agreement here is good, except for when the Mies

model is used, suggesting that the airglow derived [O] data areconsistent. Because of the uncertainty in the magnitude of the[H] profile an exact value for the transition probabilitiescannot be established. However, taking the TIME-GCM[H] as accurate and taking f(9) to be 0.32 then the value forA(9, 4)/A(9) is close to that given by Yee. It should beemphasized that while in this case the Mies values appear tobe inconsistent this does not mean that the other Miestransition probabilities are incorrect. Rather, it indicates thata new evaluation of the transition probabilities is needed.

4. Discussion

[29] Clearly the measured O2A and greenline emissionsand the derived [O] profile are inconsistent with the model

Figure 6. (top) The measured O2AVER (solid line) versus altitude compared to the four TIME-GCMpredictions (see Figure 3). (middle) Same but for greenline. (bottom) Same but for OHM (9, 4). On eachplot a vertical solid line is shown offset from a vertical dashed line taken as a zero reference line. Thissolid line represents the one sigma error as function of altitude in the derived VERS based on theuncertainties in the measured counting rates in Figure 5.

D02S05 HECHT ET AL.: TOMEX PHOTOMETER RESULTS

9 of 16

D02S05

地上からの可視域観測(300 - 560 nm)Ch.Leinertetal.:The1997

referenceofdi↵usenightskybrightness

23

Fig.20.Spectru

moftheairglow

from300nmto1µm(from

Broadfoot&Kendall1968)

地上からの可視域観測(540 - 800 nm) 24Ch.Leinertetal.:The1997


Fig.20.continued

地上からの可視域観測(740 - 1000 nm)Ch.Leinertetal.:The1997


25

Fig.20.continued

スペースシャトルから観測すると？BRO

ADFOO

T AND BELLAIRE: OBSERVATIO

NS O

F THE NIGHT AIRG

LOW

17,131

0 0

0 0

0 0

CO

C.O

-•- c',,l

o o --

• _ -

0

_

- 0

_•o _ -

0

_•o _ -

ø ¸

- ø ¸

- _ - 0

_•o _ -

• -,•

o•' -

oo

-?

- 0

_•o _

r •)

- -? _ -

•

- _o _ - _•o _

- oo

- o o c•

• EE

I

El-

FE

I

o o o

It-) --

o

I I

I I

0 0

0 0

Lr3 0

Lr3 0

IAI 0 •t/S 0 NV/S H 013-1AV•t IAI 0 •tñS 0 NV/S H 013--IAV•t

地上観測と宇宙観測とを比較すると• 地上観測によるスペクトル図：[Broadfoot and Kendall, 1968]

• スペースシャトルによる観測のスペクトル図：[Broadfoot and Bellaire, 1999]

• 輝線によっては強度が異なる：例えばO2の762 nm輝線→地球大気による吸収が存在し、地上での観測が難しいものもある

• 地上観測の方にHgの輝線が見える→街灯（水銀灯）の散乱を受けたものと考えられる。いまならNa輝線が混じるか？

寄り道(1)～VISIの場合• VISIは分光観測を行っている。特定の波長のみを切り出してイメージング的な観測をすることも可能。

• さまざまな輝線が観測できている。バンドで光るOHの発光もより鮮明に観測できるようになる予定。（近日、観測テーブル書き換え予定）

• 種子島を出発してから、はや１年ですか…（*_*）

600 800

100

500

400

300

Wavelength [nm]900

200

Inte

nsity

[R/

nm]

7000

Backward FOVForward FOV

O Na OO

O+

O2

O2

O O

※　いたるところにOH

紫外域発光の観測

• 宇宙機による上空での観測がほとんど

• 観測条件によってはnightglowとdayglowの両方が観測される

• 上：1986年1月のスペースシャトルによる観測（高度330 km）[Morrison et al., 1992]

• 左：1990年12月のスペースシャトルによる観測（高度358 km）[Feldman et al., 1992]


Fig. 19. Spectra of the nightglow from 800 A to 1400 A at 3 Aresolution. The data were obtained from the space shuttle atan altitude of 358 km on December 5, 1990. Two spectra areshown, of which the upper one was taken closer to the duskterminator. It therefore also shows OII 834 and HeI 584 (insecond order), which are features belonging to the dayglow.The zenith distance was ⇡ 85� and ⇡ 90� for the upper andlower spectrum, respectively. Ly↵ is a geocoronal line. Thecontinuum at 911 A is due to O+ recombination to the groundstate. From Feldman et al. (1992)

context it is relevant to know the airglow as seen from suchspacecraft positions. Results obtained at typical altitudesare shown in Figs. 19 and 21. The strength of the mainemission lines is also summarised in Table 13. For the OI130.4 nm and 135.6 nm lines enhanced values observed inthe tropical airglow (Barth & Scha↵ner 1976) are given. Atmid latitudes they are less intense by about one order ofmagnitude. Apart from the main emission lines shown inFig. 19, the ultraviolet region between 850 A and 1400 Ais thought to be free of nightglow emission.

The viewing line of spacecraft on the night side ofthe atmosphere may cross the terminator and continuethrough the sunlit parts of the atmosphere. Under thesetwilight conditions, dayglow features become important.E.g. the NO � bands then are excited by resonance fluo-rescence and then are much stronger, the N2 Lyman-Birge-Hopfield bands are clearly visible, and the forbidden [OII]emission at 247 nm is strong. Figure 22 shows ultravioletairglow emission observed under such conditions. An ex-cellent review on observations and modelling of both day-glow and nightglow ultraviolet emissions has been givenby Meier (1991).

c) Near infrared

From 1 µm to 3 µm, OH in a layer around 90 km heightdominates the airglow emission. There is a gap in the OHspectrum around 2.4 µm (see Fig. 27) which is importantfor balloon observations and also for the low backgroundobservations possible from Antarctica (see Sect. 4.3). Seenfrom the ground, longward of 2.5 µ airglow is only asmall addition to the thermal emission from the tropo-sphere (compare Fig. 11 in Sect. 4 above). Figures 25 and26 show the near-infrared OH spectrum at two resolu-tions, once with a low spectral resolution of �� = 160 A,and once with a higher resolution of �/�� = 250 � 800.Wavelength lists and intensities for the individual OHbands can be found in Ramsay et al. (1992) and Oliva& Origlia (1992). Obviously, the near-infrared airglow isdominated by the OH bands. They primarily also de-termine the night sky brightness in the J (1.2 µm) andH (1.6 µm) bands (Fig. 11, Sect. 4.3).

6.2. Dependence on zenith distance

In absence of atmospheric extinction, a thin homoge-neously emitting layer at height h above the Earth’ssurface shows a brightness increase towards the horizon,which is given by the so-called van Rhijn function

I(z)/I(zenith) =1q

1� [R/(R+ h)]2 sin2 z, (13)

where R = 6378 km is the radius of the earth. E.g.,for h = 100 km [I(z)/I(0)]max = 5.7 results (Roach &Meinel 1955). This situation typically applies for balloonexperiments. Figure 23 shows an example. For observa-tions from the ground, extinction and scattering changethe behaviour in particular for zenith distances > 40�.Around � = 500 nm � 600 nm a maximum airglow in-crease by about a factor of about four may be expectedat z = 75� � 80�, with the brightness decreasing againtowards the horizon (see Fig. 24 for an observation andRoach & Meinel (1955) for a selection of predicted pro-files). For shorter wavelengths, with stronger scatteringand extinction, this decrease starts already at higher ele-vations. However, appropriate models (based on realisticassumptions, including multiple scattering in a sphericalatmosphere and going down to the horizon) to accountfor the observed brightness profiles from the zenith to thehorizon have not yet been calculated. The results given inSect. 5 do not claim to be accurate near the horizon.

6.3. Variations

Airglow emission is often patchy and varying in bright-ness and spatial distribution with time. Roach & Gordon(1973) demonstrate this by showing airglow maps in timesteps of 15 minutes on the right upper corner of odd pages,


Table 13. Typical zenith brightness of nightglow emissionsa

Source Wavelength Height of Intensityb

emitting layerLy� 102.6 nm geocorona ⇡10 RLy↵ 121.6 nm geocorona 3 kR(night) � 34 kR(day)OI 130.4 nm 250 �300 km ⇡40 R (in tropical airglow)OI 135.6 nm 250 � 300 km ⇡30 R (in tropical airglow)O2

(Herzberg bands) 300 nm � 400 nm 90 km 0.8 R/A[OI] 557.7 nm 90 km 250 RNa D 589.0 nm, 589.6 nm ⇡92 km 30 R (summer)

to 100 R (winter)[OI] 630.0 nm 250 � 300 km 60 R[OI] 636.4 nm 250 � 300 km 20 RH↵ 656.3 nm geocorona 4�6 R (night)pseudocontinuum 400 nm � 700 nm 90 km 0.3 R/AO2

864.5 nm ⇡80 km 1 kROH 600 nm � 4.5 µm 85 km 4.5 MR(all bands)

aafter Chamberlain (1961), Roach (1964), Roach & Gordon (1973), Meier (1991); see also the references in the sections ongeocorona and ultraviolet airglow.btransformed to zenith, where necessary.

Fig. 21. Left: Spectrum of the nightglow from 1250 A to 1700 A at 17 A resolution. The data were obtained from the spaceshuttle at a height of 330 km in January 1986 at minimum solar activity. The oxygen OI lines at 1304 A and 1356 A are thebrightest features. For the weakly visible Lyman-Birge-Hopfield bands the dashed curve shows a predicted spectrum. Right:Spectrum of the ultraviolet nightglow from 170 nm to 310 nm at 29 A resolution obtained on the same flight. The solid lineshows an appropriately scaled solar spectrum and is assumed to show the contribution to zodiacal light. From Morrison et al.(1992)

thus enabling a “thumb-cinema” look at these spatio-temporal variations. Quantitative examples for variationduring one night or variation with solar cycle can be seenin Figs. 8 and 10 in Sect. 4. Often a systematic decreaseof airglow emission during the course of the night is ob-served, explained as result of the energy stored during dayin the respective atmospheric layers.

Figure 29 shows this for the OH emissions and alsogives an example for the wavelike structures often appar-ent in these emissions.

These examples do not give at all a full overview onairglow variability but just demonstrate that it is a typicalproperty of this source of night sky brightness.

In the visual spectral region, correlations between theprominent [OI] and NaD airglow emission lines and “pseu-docontinuum” bands at 367 nm, 440 nm, 526 nm, 558 nm,634 nm and 670 nm have been studied by Barbier (1956)who established three “covariance groups”. E.g., the cor-relation between the 557.7 nm line and the “pseudocon-tinuum” at 502 nm has been used by Dumont (1965) to

赤外域発光の観測

• 2.5μm以上の波長域では対流圏からの熱放射の割合の方が強い。

• 上：波長1.2μm以下の領域を分解能16nmで地上観測[Harrison et al., 1973]

• 右：マウナケアからの地上観測[Ramsay et al., 1992]

28Ch.Leinertetal.:The1997


0

2.0

4.0

6.0x104 (6-1) (7-2) (8-3) (4-0) (9-4) (5-1)

0.65 0.70 0.75 0.80WAVELENGTH - MICRONS

DIFF

EREN

TIAL

BRI

GHT

NESS

(ZEN

ITH)

RAYL

EIG

HS P

ER M

ICRO

N


DIFF

EREN

TIAL

BRI

GHT

NESS

(ZEN

ITH)

RAYL

EIG

HS P

ER M

ICRO

N 3.0

2.0

1.0

(9-5)(3-0)(8-4)(7-3)O2(0-1)(6-2)

x105

0


9.0

7.0

5.0

3.0

1.0

x105

DIFF

EREN

TIAL

BRI

GHT

NESS

(ZEN

ITH)

RAYL

EIG

HS P

ER M

ICRO

N

(6-3)(5-2)(4-1)

1.50 1.60

(9-7)

1.70 1.80WAVELENGTH - MICRONS

0

0.5

1.0

1.5

DIFF

EREN

TIAL

BRI

GHT

NESS

(ZEN

ITH)

RAYL

EIG

HS P

ER M

ICRO

N x106(7-5)(6-4)(5-3)(4-2)(3-1)

1.401.301.201.10WAVELENGTH - MICRONS

(2-0)(9-6)(8-5)(7-4)(6-3)(5-2)1.5

1.0

0.5

0

x106

DIFF

EREN

TIAL

BRI

GHT

NESS

(ZEN

ITH)

RAYL

EIG

HS P

ER M

ICRO

N

2.202.102.001.90WAVELENGTH - MICRONS

0

0.5

1.0

1.5

DIFF

EREN

TIAL

BRI

GHT

NESS

(ZEN

ITH)

RAYL

EIG

HS P

ER M

ICRO

N x106(8-6)

Fig.25.Near-in

fraredairglow

spectru

masseen

fromthegroundat160Aresolu

tion(for�>1.2µm).TheOHbandsmainly

contributingtotheemission

havebeenidentifiedinthefigure.“di↵erential”

simplymeans“permicron

”.From

Harrison

&Kendall(1973)


1.1 1.2 1.3 1.4 1.5Wavelength in vacuum (µm)

010

0020

0030

0040

00

Flux

(ph

oton

s-1

arc

sec-2

m-2

µm

-1)

1.95 2 2.05 2.1 2.15 2.2 2.25 2.3 2.35Wavelength in vacuum (µm)

010

0020

0030

00

Flux

(ph

oton

s-1

arc

sec-2

m-2

µm

-1)

Flux

(ph

oton

s-1

arc

sec-2

m-2

µm

-1)

Wavelength in vacuum (µm)1.5 1.55 1.6 1.65 1.7 1.75

2000

4000

6000

Fig. 26. Near-infrared airglow spectrum as observed from Mauna Kea at spectral resolution �/�� = 250�800. In regions withatmospheric transmission 0.75 the flux has been arbitrarily set to zero. Longward of 2.1 µm thermal atmospheric emissiontakes over. Note that 1000 of the units used correspond to 6.77 10�6, 5.11 10�6, and 3.84 10�6 W/m2 srµm at 1.25 µm, 1.65 µmand 2.2 µm, respectively. From Ramsay et al. (1992)

発光の時間変化

• 輝度と発光の空間分布が時間的に変化する（修士のときに似たようなでも違う話をした気が…）

• マウナケアからの地上観測[Ramsay et al., 1992]• 左：波状構造の通過に伴う分単位の輝度変化• 右：夜間の発光強度の時間変化


Fig. 29. Variation of OH airglow, observed from Mauna Kea. Left: Short term variations (minutes) caused by the passageof wavelike structures. Right: Decrease of OH airglow during the course of a night, shown for several bands separately. FromRamsay et al. (1992)

Fig. 27. Spectral distribution of near-infrared zenith airglowshowing the gap in airglow emission around 2.4 µm. The air-glow measurements have been performed from a balloon at30 km altitude during flights in 1972 and 1974. Variations fromflight to flight and during one night were less than a factor oftwo. From Hofmann et al. (1977)

Fig. 28. Correlation between the di↵use sky emission at 467nm (Stromgren b) and at � = 525 nm. The brightness varia-tions in both bands are mainly due to airglow. From Leinertet al. (1995)

radii. Two telling images of the geocorona in Ly↵, includ-ing the globe of the earth, are shown by Frank et al. (1985,see p. 63). This geocorona is optically thick to the solarLyman lines. Typical intensities of the emissions observedfrom ground (in the visual) or from earth orbit are givenin Table 13, with the data taken from Caulet et al. (1994)and Raurden et al. (1986) for Ly↵, Meier et al. (1977) forLy�, Levasseur et al. (1976) for H↵.

寄り道(2)～「れいめい」の思い出

• 修士課程では「れいめい」による約1,200観測のデータを用いて、大気光発光の季節変化（春夏秋冬）および緯度変化を調べた。

• 「れいめい」の理学観測は今年3月で終了。工学試験目的の運用はまだ続いている（はず）。

2000

1500

1000

500

050 40 30 20 10

VER

[pho

tons

/cc/

s]

Latitude [deg]

全データ (557.7nm)2000

1500

1000

500

050 40 30 20 10

VER

[pho

tons

/cc/

s]

Latitude [deg]

全データ (670nm)

異なる波長での発光の変化の相関• Barbier et al., 1956によれば、以下の輝線および波長での発光強度にはよい相関が見られる：

• O(557.7 nm etc. )• Na D線• 擬連続光中の367 nm, 440 nm, 526 nm, 558 nm, 634 nm, 670 nm

• 右：467 nmの輝線の発光強度（水平方向）と525 nmの発光強度（鉛直方向）が極めて良い相関を示している。[Leinert et al., 1995]


Fig. 29. Variation of OH airglow, observed from Mauna Kea. Left: Short term variations (minutes) caused by the passageof wavelike structures. Right: Decrease of OH airglow during the course of a night, shown for several bands separately. FromRamsay et al. (1992)

Fig. 27. Spectral distribution of near-infrared zenith airglowshowing the gap in airglow emission around 2.4 µm. The air-glow measurements have been performed from a balloon at30 km altitude during flights in 1972 and 1974. Variations fromflight to flight and during one night were less than a factor oftwo. From Hofmann et al. (1977)

Fig. 28. Correlation between the di↵use sky emission at 467nm (Stromgren b) and at � = 525 nm. The brightness varia-tions in both bands are mainly due to airglow. From Leinertet al. (1995)

radii. Two telling images of the geocorona in Ly↵, includ-ing the globe of the earth, are shown by Frank et al. (1985,see p. 63). This geocorona is optically thick to the solarLyman lines. Typical intensities of the emissions observedfrom ground (in the visual) or from earth orbit are givenin Table 13, with the data taken from Caulet et al. (1994)and Raurden et al. (1986) for Ly↵, Meier et al. (1977) forLy�, Levasseur et al. (1976) for H↵.

シャトルグロー• 衛星（宇宙機）の高度と太陽活動度によっては、大気との作用によって赤色～近赤外域での発光が見られる。紫外域での発光もある。

• N2 Lyman-Birge-Hopfield band(120 - 280 nm)について

• 太陽活動が中程度の時期に高度250 kmで100 - 500 R/nm　 [Torr et al., 1985]

• 太陽活動静穏時では高度330 kmでも観測されなかった [Morrison et al., 1992]

• 上：STS-062ミッション(1994年3月)での観測

「光汚染」• 全天イメージャはたいてい人里離れたところに置かれる；街灯りによって空が「汚染」されるから。

• [Walker 1970, 1977]など都市の明かりによる光害の観測例がイタリア／カナダ／アメリカで存在する。Walkerによれば以下のものが導かれる（らしい）；(1) 人口と街の明るさの相関(2) 空の明るさを都市からの距離の函数として表す(3) 人口の増え方と都市からの光汚染の具合の間には定量的な増加関係がみられる


7. Light pollution

Artificial lighting at earth contributes via troposphericscattering to the night sky brightness over a large areaaround the source of light. Both a continuous componentas well as distinct emission lines are present in the lightpollution spectrum. A recent review of sky pollution isgiven in McNally (1994).

7.1. Observations of sky pollution

Systematic broad-band observations of the sky pollutionlight near cities have been carried out by Bertiau et al.(1973) in Italy, Berry (1976) in Canada & Walker (1970,1977) in California. Berry showed that there is a relation-ship between the population of a city and the zenith skybrightness as observed in or near to the city. Walker inter-preted his extensive observations by deriving the followingrelationships: (1) between the population and luminosityof a city; (2) the sky brightness as a function of distancefrom the city; and (3) between the population and thedistance from a city for a given sky pollution light contri-bution. The last two relationships are shown in Figs. 31and 32. These figures can be utilized to derive an estimatefor the sky pollution at 45 deg altitude caused by a citywith 2000�4 million population and with a similar streetlighting power per head as California. Starting with thecity population Fig. 31 gives the distance at which theartificial lighting contribution increases the natural skybrightness by 20% (0.2 mag/200). With this distance onecan enter Fig. 32 and obtain a scaling for the (arbitrary)intensity axis of this figure. Thus the artificially causedsky brightness at 45 deg altitude at 6 � 200 km distancefrom the city can be estimated from this figure.

7.2. Modelling of sky pollution

Treanor (1973) and Bertiau et al. (1973) have used anempirical formula, based on a simplified model of the tro-pospheric scattering, to fit the sky pollution observationsnear cities. Garstang (1986, 1989a,b, 1991) has used radia-tive transfer models including 1st and 2nd order Rayleighand aerosol scattering, e↵ects of ground albedo and cur-vature of the earth’s surface, and the areal distribution ofthe light source to calculate the sky pollution light inten-sity. He has compared and scaled his model results againstthe above mentioned observational results. Garstang’s fit-ted models are shown in Figs. 31 and 32. superimposedon the observational points of Walker (1977). Garstang(1986, 1989a,b) gives also the calculated zenith distancedependence of the sky pollution light intensity both to-wards and away from the source of light. These resultsare reproduced in Fig. 33.

Fig. 31. Variation with city population of the distance atwhich the lights of a city produce an artificial increase ofthe night sky brightness at 45 deg altitude toward the cityby 0.20 mag. This increase refers to an assumed natural skybrightness of V = 21.9 mag/200. Observations by Walker(1977) are indicated by dots. Two models by Garstang (1986)are shown as solid lines. K is a measure for the relative impor-tance of aerosols for scattering light. The uppermost dot refersto Los Angeles County, the cross below it to Los Angeles City.From Garstang (1986)

7.3. Spectrum of the sky pollution light

The emission line spectra of the di↵erent types of streetlamps are visible in the night sky light even at good ob-servatory sites, such as Kitt Peak in Arizona. While themost commonly used street lamps until the 1970’s werefilled with Hg there has been since then a general changeover to sodium lamps, both of the high pressure (HPS)and low pressure sodium (LPS) types. The most impor-tant sky pollution lines are given in Table 14 according toOsterbrock et al. (1976), Osterbrock & Martel (1992) andMassey et al. (1990). At good sites (e.g. Kitt Peak), thestrongest pollution lines are about a factor of two weakerthan the strongest airglow lines. The opposite is true forstrongly contaminated sites (e.g. Mt Hamilton). Whereasthe pollution lines are normally restricted to a relativelynarrow wavelenth range the Na D line wings producedby the HPS lamps are extremely broad, extending over5700� 6100 A. Thus the LPS lamps are highly preferableover the HPS ones from the astronomer’s point of view.

Other studies of the night sky spectrum, including theartificial pollution lines, have been presented by Broadfoot& Kendall (1968) for Kitt Peak, Turnrose (1974) for Mt.Palomar and Mt. Wilson, and Louistisserand et al. (1987)for Pic du Midi.

光汚染の経験モデル• [Garstang 1986, 1989a,b, 1991]のモデルでは以下のものが考慮されている：

• 1次と2次のレイリー散乱

• エアロゾルによる散乱

• 地面による光の反射（表面の状況も含めて）

• 光源の面分布の様子

• 天頂角依存性

• 街灯が「水銀灯→high pressure sodium type→low pressure sodium type」と変化

• 人工光(Hg, Na, K)のスペクトルのピークがだんだん長波長側に移動してきている


Fig. 32. Variation with distance from the city of the skybrightness at 45 deg altitude in the direction of the city. Thedots indicate observations in V band by Walker (1977) nearthe city of Salinas. The solid curves are according to mod-els by Garstang (1986). The brightness ratio is defined asb(Salinas at +45�)�b(Salinas at �45�)b(sky background only at +45�)

, where b = sky brightness.

Zenith distance +45� is towards and �45� away from the city.The solid curves are according to models by Garstang (1986).Curve 1: L

0

= 986 lumens per head, K = 0.43, F = 11%.Curve 2: L

0

= 1000 lumens per head, K = 0.5, F = 10%. L0

isthe artificial lighting in lumens produced per head of the pop-ulation. K is a measure for the relative importance of aerosolsfor scattering light. F : a fraction F of the light produced bythe city is radiated directly into the sky at angles above thehorizontal plane, and the remainder (1�F ) is radiated towardthe ground. The dashed line is the relation ⇠ D�2.5. FromGarstang (1986)

8. Zodiacal light

8.1. Overview and general remarks

The zodiacal light in the ultraviolet, visual and near-infrared region is due to sunlight scattered by the inter-planetary dust particles. In the mid- and far-infrared itis dominated by the thermal emission of those particles.Zodiacal light brightness is a function of viewing direction(� � ��, �), wavelength, heliocentric distance (R) andposition of the observer relative to the symmetry planeof interplanetary dust. Its brightness does not vary with

Fig. 33. Zenith distance dependence of sky pollution light ac-cording to the model calculations of Garstang (1986). Resultsare for sky pollution due to Denver as seen from a distanceof 40 km in the vertical plane containing the observer and thecenter of Denver. Curve 1: sky background; Curve 2: Denveronly; Curve 3: Denver and sky background. Negative zenithdistances are away from Denver. From Garstang (1986)

λ - λ (°)

Ι [ S

10

]

Levasseur-Regourdand DumontHelios A and BPioneer 10

β = 16.2°

β = 31.1°

30 60 90 120 150 180

103

600

300

100

60

Fig. 34. Comparison of zodiacal light measurements along thebands of constant ecliptic latitude � = 16.2� and � = 31.0� ob-served by Helios A and B. The ground-based measurements ofLevasseur-Regourd & Dumont (1980) at �

e↵

= 502 nm havebeen linearly interpolated to these latitude values. The Heliosmeasurements at B and V (Leinert et al. 1981) have been lin-early interpolated to �

e↵

= 502 nm. The Pioneer measurements(Toller & Weinberg 1985) have been extrapolated from blue to502 nm with the values applicable for Helios and from � =10� to � = 16� according to the table of Levasseur-Regourd &Dumont (1980). For definition of the S10� unit see Sect. 2


Fig. 32. Variation with distance from the city of the skybrightness at 45 deg altitude in the direction of the city. Thedots indicate observations in V band by Walker (1977) nearthe city of Salinas. The solid curves are according to mod-els by Garstang (1986). The brightness ratio is defined asb(Salinas at +45�)�b(Salinas at �45�)b(sky background only at +45�)

, where b = sky brightness.

Zenith distance +45� is towards and �45� away from the city.The solid curves are according to models by Garstang (1986).Curve 1: L

0

= 986 lumens per head, K = 0.43, F = 11%.Curve 2: L

0

= 1000 lumens per head, K = 0.5, F = 10%. L0

isthe artificial lighting in lumens produced per head of the pop-ulation. K is a measure for the relative importance of aerosolsfor scattering light. F : a fraction F of the light produced bythe city is radiated directly into the sky at angles above thehorizontal plane, and the remainder (1�F ) is radiated towardthe ground. The dashed line is the relation ⇠ D�2.5. FromGarstang (1986)

8. Zodiacal light

8.1. Overview and general remarks

The zodiacal light in the ultraviolet, visual and near-infrared region is due to sunlight scattered by the inter-planetary dust particles. In the mid- and far-infrared itis dominated by the thermal emission of those particles.Zodiacal light brightness is a function of viewing direction(� � ��, �), wavelength, heliocentric distance (R) andposition of the observer relative to the symmetry planeof interplanetary dust. Its brightness does not vary with

Fig. 33. Zenith distance dependence of sky pollution light ac-cording to the model calculations of Garstang (1986). Resultsare for sky pollution due to Denver as seen from a distanceof 40 km in the vertical plane containing the observer and thecenter of Denver. Curve 1: sky background; Curve 2: Denveronly; Curve 3: Denver and sky background. Negative zenithdistances are away from Denver. From Garstang (1986)

λ - λ (°)

Ι [ S

10

]

Levasseur-Regourdand DumontHelios A and BPioneer 10

β = 16.2°

β = 31.1°

30 60 90 120 150 180

103

600

300

100

60

Fig. 34. Comparison of zodiacal light measurements along thebands of constant ecliptic latitude � = 16.2� and � = 31.0� ob-served by Helios A and B. The ground-based measurements ofLevasseur-Regourd & Dumont (1980) at �

e↵

= 502 nm havebeen linearly interpolated to these latitude values. The Heliosmeasurements at B and V (Leinert et al. 1981) have been lin-early interpolated to �

e↵

= 502 nm. The Pioneer measurements(Toller & Weinberg 1985) have been extrapolated from blue to502 nm with the values applicable for Helios and from � =10� to � = 16� according to the table of Levasseur-Regourd &Dumont (1980). For definition of the S10� unit see Sect. 2

天文観測では• 非常に遠くの銀河（多くは赤方偏移している）を観測することも多く、遠くにある天体からの光量が小さい場合も往々にしてあるので以下の「光」も問題になる（省略しますが）：

• 黄道光• 太陽コロナの明るさおよびpolarization• （観測したい天体以外の）星明かり←Pioneer 10号／11号での見積もり例もあるらしい

• 散乱銀河光• 宇宙空間全体の背景放射（いわゆる3K波とか）

まとめ• 地上には大気光以外にもさまざまな「光」が降り注いでいる。それらの定量的な見積もりによってより精度の高い観測を行うことが可能となる。

• 地上からも光は放出されていて、それらの対流圏での散乱の効果は無視できない。

• 大気光の発光領域は紫外域から赤外域まで広がっている。発光源の違いによって大きく異なる特徴を示す。

以上です。• 祇園祭、宵山ですね。

• 本当はこれらの写真を「イメージング観測」の例として出したかった…（出したら本題には戻って来れないだろうな）Architectural Institute of Japan

NII-Electronic Library Service

左２点：森田「京都・鴨川河川敷に坐る人々の空間占有に関する研究」(1987)

Architectural Institute of Japan

NII-Electronic Library Service

上３点：2013年5月から6月にかけての鴨川右岸イメージング観測。

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天文観測の観点からの 「夜間の発光」についてのレビュー …step0ku.kugi.kyoto-u.ac.jp/~akiya/prefiles/20130716.pdf · 1 Max–Planck–Institut f¨ur Astronomie,

天文観測の観点からの「夜間の発光」についてのレビュー …step0ku.kugi.kyoto-u.ac.jp/~akiya/prefiles/20130716.pdf · 1 Max–Planck–Institut f¨ur Astronomie,