Maynoo h Op ical Ae onomical Facili y
F ancis J. Mulligan
S . Pa ick's College
Depa men o Expe imen al Physics
Maynoo h, Co. Kilda e, I eland
E-mail: mulligan@ axl .may.ie
Rick J. Niciejewski
Uni e si y o Michigan
Space Physics Resea ch Labo a o y
Depa men o A mosphe ic, Oceanic and
Space Sciences
2455 Haywa d
Ann A bo , Michigan 48109
1 In oduc ion
a e impo an in helping o elucida e he complex dynamical
and chemical p ocesses ha in luence a mosphe ic compo-
si ion. Balloon' and ocke -bo ne2 expe imen s ha e enabled
a mosphe ic scien is s o make measu emen s in he opo-
sphe e and s a osphe e, while sa elli es such as Dynamics
Explo e II ha e p o ided global co e age a much highe
al i udes.3 The mesopause, loca ed nea an al i ude o 87 km,
has p o ed o be one o he mos di icul egions o s udy
expe imen ally, being oo high o balloon and oo low o
sa elli e obse a ions. The majo i y o obse a ions in his
egion ha e been ob ained ei he by ocke sounding o by
emo e sensing o na u ally occu ing emissions in he in-
a ed, isible, o ul a iole spec um. Rocke expe imen s
p o ide excellen co e age in al i ude a a pa icula ime and
loca ion, bu hey a e no capable o p o iding long- e m
measu emen s. Lida echniques o e he g ea es po en ial
o p o iding high- esolu ion empe a u e and wind measu e-
men s a s a osphe ic and mesosphe ic al i udes, bu i is
only e y ecen ly ha lida echniques ha e de eloped so
ha he egion nea he mesopause can be s udied using his
echnique.4 The measu emen o a mosphe ic empe a u e
and wind eloci y by obse ing ai giow emissions con ined
o na ow al i ude bands con inues o be one o he mos cos -
e ec i e me hods a ailable.
Essen ially all ai glow s udies a e made du ing he hou s
o da kness, because o he di icul y o disc imina ing agains
he o e whelming sola backg ound du ing dayligh hou s.
Many measu emen s ha e been made a high la i udes, whe e
good wea he condi ions, oge he wi h con inuous da kness
in win e , allow long se ies o obse a ions o be ob ained.57
I eland is no an ideal loca ion in which o place an obse ing
Pape 01-024 ecei ed Ap . 25, 1994; e ised manusc ip ecei ed Aug. 29, 1994;
accep ed o publica ion Aug. 29, 1994.
1994 Socie y o Pho o-Op ical Ins umen a ion Enginee s. 009 I-3286/94/$6.00.
si e o g ound-based op ical obse a ions. Poo and e y
a iable wea he condi ions oge he wi h high ela i e hu-
midi y and he absence o sui able high-al i ude obse ing
si es pose he g ea es p oblems. The e y di icul y o ob-
aming such measu emen s, howe e , ende s hei signi i-
cance all he g ea e , pa icula ly in helping o cons ain
global a mosphe ic models ha o en su e om a lack o
da a poin s in ce ain la i ude and longi ude sec o s. Figu e 1
aken om Re . 8 shows he global dis ibu ion o op ical
s a ions in ol ed in uppe a mosphe e s udies.8 I eland's po-
si ion on he wes e n pe ime e o Eu ope ep esen s an im-
po an loca ion in illing he oid be ween he Uni ed S a es
and mainland Eu ope.
Qui e dis inc om he ole ha an a mosphe ic obse ing
si e in I eland can play as an elemen in a global g id o
s a ions, i s la i ude is in he cen e o he ange whe e high
al i ude (—82 km) noc ilucen clouds (NLCs) a e obse ed
du ing wiligh in summe . NLCs a e obse ed mos e-
quen ly in he la i ude egion 50° o60° on ei he side o he
equa o in summe mon hs, when he sun is be ween 6° and
1 6° below he ho izon. They a e impo an in mesosphe ic
physics because hey lie close o he mesopause, and because
i appea s ha hei equency o occu ence is on he inc ease.
I is belie ed ha his may be ela ed o inc easing concen-
a ions o me hane coupled wi h dec easing mesosphe ic
empe a u es. The ideal zone o iewing hem9 is 53° o57°.
F om his poin o iew, I eland should be a good loca ion
om which o unde ake a s udy o he co ela ion be ween
noc ilucen cloud o ma ion and mesopause empe a u e.
The ole o in e nal g a i y wa es in main aining he he -
mal s uc u e o he mesopause is cu en ly he subjec o a
numbe o in es iga ions .'0 1 2 These wa es p opaga e
h ough he s a osphe e and mesosphe e and dissipa e hei
ene gy nea he mesopause. T oposphe ic con ec ion, o o-
g aphic e ec s, and e en la ge-scale ocean wa es a e be-
lie ed o be sou ces o hese wa es. I eland's loca ion a he
edge o a as expanse o open wa e wi h a p e ailing wes-
e ly wind sugges s ha i migh also be a good place om
OPTICAL ENGINEERING/Decembe 1994 / Vol. 33 No. 12/3853
Abs ac . G ound-based measu emen s o uppe a mosphe ic pa ame-
e s, such as empe a u e and wind eloci y, can be made by obse ing
ai glow emissions ha ha e a well-de ined al i ude p o ile and ha a e
known o be ep esen a i e o he emi ing egion. We desc ibe he op-
ical obse a o y a Maynoo h (53.23° N, 6.4° W) a which wo ins u-
men s, a Fab y-Pé o in e e ome e and a Fou ie ans o m spec om-
e e , a e used o eco d a mosphe ic ai glow emissions in I eland a
isible and nea -in a ed wa eleng hs, espec i ely. Desc ip ions o he
ins umen s, da a acquisi ion, and analysis p ocedu es a e p o ided, o-
ge he wi h some sample esul s.
Subjec e ms: op ical obse a o ies; ai glow obse a ions; g ound-based; meso-
sphe ic measu emen s.
Op ical Enginee ing 33(12), 3853—3860 (Decembe 1994).
Measu emen s o a mosphe ic pa ame e s such as empe a-
u e and wind eloci y, as a unc ion o ime and loca ion,
80
60
40
20
0
20
40
60
MULLIGAN and NICIEJEWSKI
Fig. 1 Wo ldwide map o op ical a mosphe ic obse a o ies (a e Re . 8).
which o sea ch o sho -pe iod (10 o 20 mm) g a i y wa es,
since i has been sugges ed ha he in e ac ion o s ong winds
wi h moun ains migh be a sou ce o lee- ype g a i y 2
This pape desc ibes a small op ical obse a o y loca ed
on he campus a Maynoo h College (53.2°N,6.4° W), which
houses a Fou ie ans o m spec ome e and a Fab y-Pé o
in e e ome e , o he pu pose o measu ing empe a u e and
wind eloci y in he uppe mesosphe e and lowe he mo-
sphe e egion. Desc ip ions o he ins umen s, da a acqui-
si ion, and analysis p ocedu es a e p o ided, oge he wi h
some sample esul s. Da a eco ded a Maynoo h o m pa
o a g ound-based alida ion campaign o he Uppe A -
mosphe e Resea ch Sa elli e, h ough a collabo a ion wi h
he Space Physics Resea ch Labo a o y o he Uni e si y o
Michigan.
2 Ins umen Desc ip ions
2.1 Fou ie T ans o m Spec ome e
The Fou ie ans o m in a ed (FTIR) spec ome e is based
on a Michelson in e e ome e design and was supplied by
Bomem Inc. A he moelec ically cooled InGaAs de ec o is
employed, which has maximum sensi i i y in he wa eleng h
egion 1 o 1.65 im. This ange includes he o a ional bands
associa ed wi h ( =2) ib a ional ansi ions o he hy-
d oxyl molecule. An in e nal He-Ne lase p o ides accu a e
da a sampling, and he ins umen has a maximum esolu ion
o 2cm .In his s udy, he esolu ion is se a 4 cm ,which
enables a comple e in e e og am o be acqui ed in abou 5s
and ep esen s a comp omise be ween in eg a ion ime and
esolu ion. The ins umen has a ield o iew o 1 .5deg
and ypically 50 in e e og ams a e coadded o inc ease he
signal- o-noise a io. The composi e in e e og am is apod-
ized using he Hanning window, and a spec um is ob ained
by Fou ie ans o ming he apodized in e e og am. The el-
a i e spec al esponse o he de ec o is de e mined by cal-
ib a ion wi h a low b igh ness sou ce (LBS) whose a ea is
su icien o comple ely ill he ield o iew o he ins umen
and is simila in cons uc ion o ha desc ibed by Dandeka
and Da is.'3 The calib a ion o he low b igh ness sou ce is
aceable o a p ima y s anda d, and we es ima e ha adi-
ances calcula ed on he basis o his sou ce a e accu a e o
10 o 15%. Figu e 2, eco ded sho ly a e midnigh on 5
Sep embe 1993 wi h an in eg a ion ime o 4.5 mm, is a
ypical spec um showing bo h he OH(3,l) and (4,2)
ib a ion- o a ion bands. The al i ude o maximum emission
o hese bands in he nigh ai glow is nea 87 km.
2.2 Fab y-Pé o In e e ome e
The Fab y-Pé o in e e ome e (FPI) was designed and con-
s uc ed in he Depa men o Expe imen al Physics a May-
noo h College, wi h a iew o eco ding he spec al line
3854 IOPTICAL ENGINEERING I Decembe 1 994 I Vol. 33 No. 12
180 160 140 120 100 80 60 4020 0 20 40 60 80 100 120 140 160 180
C.02.O>(I)Ca,C
MAYNOOTH OPTICAL AERONOMICAL FACILITY
Da a acquisi ion and con ol 80386 compu e and CAMAC modules
p o ile associa ed wi h he a omic oxygen emissions a 557.7
and 630 nm; wa eleng h selec ion is achie ed using na ow
passband il e s (2 and 6 A, espec i ely). De ails o he in-
s umen pa ame e s a e lis ed in Table 1 .Thede ec o , which
was p o ided by he Uni e si y o Michigan, is one o a se ies
o de ices de eloped o he Fab y-Pé o in e e ome e on
boa d he Dynamics Explo e II sa elli &4 and has also been
used o g ound-based s udies a high I comp ises
an S20 pho oca hode o diame e 1 .2 cm, h ee mic ochannel
pla es as he gain elemen , and an anode comp ising 1 2 con-
cen ic annuli each o equal a ea. The de ice ope a es as i
i we e 12 dis inc pho omul iplie ubes, wi h a sepa a e
coun ing channel o each anode. Da k coun s a e educed
by cooling he de ec o using a he moelec ic coole , which
educes he empe a u e a he ca hode by abou 40°C below
ambien . Condensa ion on he de ec o window is p e en ed
by he use o a he mopane window.
The Fab y-Pé o pla es a e op ically con ac ed using h ee
ze odu space s, 1 cm in heigh , and a e moun ed in a igid
in a cage enclosed in a p essu e-sealed aluminium housing.
Fine pa allelism adjus men is achie ed by applying p essu e
o he pla es o e he ze odu space s ia in a sp ings. The
con ac a ea be ween he housing and he Fab y-Pé o pla es
is kep o a minimum o educe he conduc ion o hea o he
d alon h ough he moun .
Fab y-Pd o inges a e ocused on o he de ec o ia a
1- n ocal leng h lens. The op ical sys em is such ha he 12
channels o he de ec o in e cep abou 60% o a ull ee
spec al ange. The choice o op ical pa ame e s is a co n-
p omise be ween ob aining a good desc ip ion o a line p o ile
in he 12 channels, i.e., ha he sky p o ile s addles a leas
6 o 7 channels, while a he same ime enabling he back-
g ound signal le el o be es ablished accu a ely. Posi ioning
o an in e e ence inge in he cen e o he 1 2 channels is
achie ed by changing he p essu e in he sealed é alon hous-
ing ia a mo o -d i en p essu e con olle , which is unde
he con ol o he da a acquisi ion compu e . The p essu e
con olle also plays a i al ole in de e mining he ins umen
esponse as desc ibed in Sec. 3.
The con ol and in e ace elec onics a e a combina ion
o comme cial uni s and labo a o y speci ic modules designed
and cons uc ed wi h he measu emen s in mind. The high
ol age o he de ec o oge he wi h he p eampli ie s, dis-
c imina o s, and pulse shape s we e buil a he Uni e si y
o Michigan. This dedica ed elec onics is con olled by an-
alog and digi al I/O lines om he da a acquisi ion compu e .
Pulse coun ing is achie ed h ough he use o CAMAC ime
and coun e modules, which a e also unde he con ol o he
compu e . A simpli ied block diag am o he en i e ins umen
is shown in Fig. 3. Figu e 4(a), eco ded on 26 Sep embe
1993 a 2:34 uni e sal ime (U.T.) wi h an in eg a ion pe iod
o 2 mm, is a ypical sky p o ile ob ained when obse ing
he a omic oxygen 0'S 557.7-nm emission. A midla i udes,
his emission comes p edominan ly om an al i ude nea
95 km. Channels 10 and 12 ha e conside ably di e en da k
Fig. 3 Block diag am o Maynoo h Fab y-Pé o in e e ome e .
OPTICAL ENGINEERING / Decembe 1994 / Vol. 33 No. 12 / 3855
4.0
Nea in a ed spec um eco ded a Maynoo h
5 h Sep embe .1993 0.4 UT. Table 1 Maynoo h Fab y-Pé o in e e ome e cha ac e is ics.
0.06000 6400 6800 7200 7600 8000
Wa enumbe (cm-I)
Pla e diame e 12.7 cm
Pla e sepa a ion 1 .0 cm
Re lec i i y (A) a 557.7 nm 0.82
F ee Spec al ange 0.155 A
Ins umen al inesse 10
Objec i e lens =100 cm
Field o iew 0.34°(ha angle)
In e e ence il e 0.6 nm (T,,, = 40%)
De ec o Type ITT F3035 concen ic ing anode;
mic ochannel pla e elec on mu iplie
S20 pho oca hode; 12 mm diame e (TE
cooled).
Spec al calib a ion F equency s abilized He-Ne lase
Signal in eg a ion ime 5 minu es o in ensi ies > 100 A
Fig. 2 Nea -in a ed spec um eco ded sho ly a e midnigh a
Maynoo h on 5 Sep embe 1993 (in eg a ion ime: 4.5 mm).
(a) (b)
Fig. 4 (a) 01S 557.7-nm p o ile eco ded a Maynoo h on 26 Sep embe 1993 a 2.34 UT (in eg a ion
ime: 2 mi, (b) Bes - i syn he ic Q15 557.7-nm p o ile (in leas -squa es sense) o ha shown in
(a) o an emission empe a u e o 208 K and a line-o -sigh eloci y o 24 m/s.
3856 / OPTICAL ENGINEERING / Decembe 1994 / Vol. 33 No. 12
=ln{ N1E(J')
Q (T o )S
—
kT o
1 6000
1 4000
1 2000
1 0000
6000
6000
4000
2000
0
U,C00
MULLIGAN and NICIEJEWSKI
1 6000
1 4000
1 2000
1 0000
8000
U,C00 6000
4000
2000
0
Channel Channel
coun s and sensi i i y compa ed wi h channels 1 o 9 as in- F _E( J')l
dica ed in Fig. 4(a). The absence o coun s in channel 11 was Q '(T o ) 2(2 J' + 1) expL kT o j(2)
caused by he ac ha channel 1 1 was inope a i e in he
de ec o employed in his s udy. Equa ion (1) may be con e ed o a linea equa ion in he
3Tempe a u e Calcula ion Technique ollowing o m:
3.1 OH Emission ln1
Ro a ional empe a u es o hyd oxyl emissions a e de e - 2(2J' + l)A(JVJ V)}
mined om he in ensi y dis ibu ion o he o a ional lines.
The li e ime o he ib a ional s a e is su icien ly long-li ed (3)
o he emi ing molecule o each he mal equilib ium wi h
i s su oundings'6; he o a ional le els a e hus popula ed The o a ional empe a u e can be ob ained om he slope
acco ding o a Bol zmann dis ibu ion. Fo an emission a a o a plo o he le -hand side e sus E ( J'). Fo an emi ing
empe a u e T o ' he in ensi y o a o a ional line is gi en sou ce in he mal equilib ium, such a plo is a s aigh line.
by'7: The unce ain y o he linea i is a measu e o he empe -
a u e unce ain y. The in e cep on he plo may be used o
I( J', '9J", ' ) = de e mine he in ensi y o he emission.
Ins umen esponse is measu ed a he beginning and end
2(2J' + 1) [— E(J')]
o each obse ing nigh . Following a nigh o obse a ions,
NV'A(J', '3J", ") exp kT '(1) each spec um o he o m shown in Fig. 2 is co ec ed o
Q'(T o ) o ins umen esponse and p ocessed acco ding o he me hod
ou lined abo e. In his s udy, he h ee mos in ense lines
whe e N is he numbe o molecules in he ' ib a ional P1(2), P1(3), and P1(4) o he ansi ion om ib a ional s a e
le el, J ' is he uppe o a ional s a e angula momen um, 3 o ib a ional s a e 1 a e used o ob ain he empe a u e.
A(J'V'JV') is he Eins ein coe icien o spon aneous emis- These a e among he mos in ense lines in he spec um and
sion om ib a ion- o a ion s a e ( J', ') o s a e J", ", and a e no a ec ed o any signi ican ex en by wa e apo ab-
E(J') is he e m alue o he uppe s a e. The e m Q, is p'7 This esul s in a sequence o empe a u e and
he pa i ion unc ion o s a e sum and is gi en by in ensi y alues o he nigh in ques ion. Figu e 5(a), which
MAYNOOTH OPTICAL AERONOMICAL FACILITY
Mesopause empe a u e calcula ed om
OH(3, 1 ) band, 1 s Sep embe , 1 993
240 I
230
220
a) 210
Cua 200
EI180
170 I
20 21 22 23 012345
Time U.T.
(a)
In eg a ed band in ensi ies o
OH(3, 1 ) band, 1 s Sep embe , 1 993
140 J
I30 :+
120
110
. 100 I+0
a) 90
," +++I II
—80 I
1+C11 II
70 •1
60 III
20 21 22 23 01234
Time U.T.
(b)
Fig. 5 (a) Tempe a u e alues calcula ed om OH(3,1) spec a e-
co ded by he Maynoo h FTIR on nigh o 1—2 Sep embe 1993.
(b) In eg a ed band in ensi ies o OH(3,1) emission eco ded by he
Maynoo h FTIR on nigh o 1—2 Sep embe 1993.
shows he a ia ion in de i ed empe a u e du ing he nigh
o 1—2 Sep embe 1993, is ypical o he esul s ob ained
h oughou he yea . Eins ein coe icien s we e ob ained om
Mies.'8 Pa i ion unc ion alues we e ob ained om K as-
so sky, She o , and Ya in,19 while o a ional e m alues
we e aken om Coxon.2° Figu e 5(b) shows he co espond-
ing in ensi y a ia ions o he same nigh . S a is ical e o s
on bo h o a ional empe a u e and band in ensi y ob iously
depend on ai glow in ensi y, which was ound o a y by as
much as a ac o o 3 du ing a single nigh . A imes o s ong
OH emission, s a is ical unce ain y in he calcula ed o a-
ional empe a u es d opped o as low as K. Typically,
abou 170 spec a we e eco ded in a single nigh du ing
midwin e , dec easing o only abou 50 in midsumme .
3.2 Oxygen 01 S Emission
The Dopple b oadening o an emission line, wi h an un-
shi ed nominal wa eleng h X0 om a sou ce in he mal equi-
lib ium a a empe a u e T is gi en as
1/2
[2kTln(2)] ,(4)
whe e k is Bol zmann' s cons an , c is he speed o ligh , and
m is he mass o he emi ing a om. Any line-o -sigh Dopple
shi X is used o de e mine a wind eloci y ec o om
he ela ion
=—c . (5)
xo
Combiningobse a ions om each o he ca dinal di ec ions
(no h, sou h, eas , wes ) allows a wind eloci y ec o o be
de e mined o he obse ing s a ion.
The spec al line eco ded by he Fab y-Pé o in e e -
ome e is a con olu ion o he Dopple b oadened emission
line sou ce and ins umen al b oadening. I is he e o e nec-
essa y o decon ol e hese wo e ec s be o e a ibu ing a
empe a u e o he emi ing egion. In his s udy, he ins u-
men al p o ile was de e mined by eco ding he ou pu om
he ins umen when illumina ed uni o mly by a equency
s abilized He-Ne lase ha emi s a spec al line o negligible
Dopple wid h a 632.8 nm. The esponse o each o he 12
de ec o channels is eco ded as a unc ion o p essu e o e
h ee ee spec al anges. This allows he calcula ion o he
ins umen al esponse in e ms o a se ies o Fou ie sine and
cosine coe icien s o each channel as desc ibed by Killeen
and Hays.2' These coe icien s a e hen co ec ed o he
change in wa eleng h om 632.8 nm o he wa eleng h o
he oxygen 0'S emission, which is a 557.7 nm. Syn he ic
p o iles a e gene a ed by con ol ing he ins umen desc ip-
ion wi h gene a ed Gaussian p o iles o known alues o
empe a u e, wind eloci y, signal, and backg ound in ensi y.
A nonlinea leas -squa es i ing app oach is used o de e -
mine he op imum i be ween he gene a ed and eco ded
p o ile. The alues o empe a u e, wind eloci y, signal, and
backg ound in ensi y a e hen assigned o he emi ing al i ude
a he ime o he obse a ion. Figu e 4(b) shows he bes - i
syn he ic p o ile o he measu ed p o ile shown in Fig. 4(a)
o an emission empe a u e o 208 K, and a line-o -sigh
wind eloci y o 24 mIs. Figu e 6(a) shows an example se
o empe a u es eco ded on 26—27 Sep embe 1 993 using
his me hod, while Fig. 6(b) shows he co esponding zonal
wind eloci ies.
4En i onmen al Conside a ions and
Da a-Taking P ocedu e
Theobse a o y was designed o allow he wo ins umen s
o unc ion in daily una ended ope a ion. The obse e yp-
ically ini ia es he obse ing p og am be o e lea ing in he
e ening; he p og am hen wai s un il he sky becomes sui -
ably da k as de e mined by a ligh senso , be o e commencing
obse a ions. Wi h he app oach o dawn he ins umen s
cease obse ing and e u n o he do man s a e. The layou
o he obse a o y, wi h sepa a e ooms o he Fab y-Pé o
in e e ome e , Fou ie ans o m spec ome e , and con ol
oom, is shown in Fig. 7.
The empe a u e o he oom housing he Fab y-Pé o in-
e e ome e is con olled o be e han 0. 1°C so as o a oid
unin ended shi s in he posi ion o he inge peak due o
empe a u e e ec s. Ligh om he sky en e s he oom
h ough a clea Pe spex dome and is di ec ed owa d he
OPTICAL ENGINEERING / Decembe 1994 / Vol. 33 No. 12 / 3857

MULLIGAN and NICIEJEWSKI
(b)
Fig. 6 (a) Tempe a u e alues calcula ed om 01S 557.7-nm p o-
iles eco ded by he Maynoo h FPI on nigh o 26—27 Sep embe
1993. (b) Zonal wind eloci ies (eas is posi i e) as a unc ion o ime
om 557.7-nm emission eco ded a Maynoo h on nigh o 26—27
Sep embe 1993.
Fab y-Pé o in e e ome e by a mi o sys em moun ed in
he dome. The posi ion o he mi o in azimu h and al i ude
is con olled by he da a acquisi ion compu e . A small ing
hea e posi ioned a he base o he dome dissipa ing abou
250 Wo hea is su icien o keep he dome clea o con-
densa ion a all imes. Du ing calib a ions, ligh om he sky
is p e en ed om en e ing he oom by a shu e , which ac s
as a e lec ion sc een o he calib a ion sou ce.
The FTIR ins umen has been designed o be used in
demanding condi ions, and i does no ha e he s ingen
en i onmen al equi emen s o he Fab y-Pé o in e e om-
e e . An iden ical ins umen has been employed o ob ain
measu emen s om an ai c a du ing he Ai bo ne Lida and
Obse a ions o he Hawaiian Ai giow Campaign
(ALOHA-90).22 I is supplied wi h da a acquisi ion so wa e
om he manu ac u e , which can be ailo ed o he use 's
needs h ough he use o keys oke mac os. This ins umen
was placed in a second oom in he obse a o y ha was i ed
wi h an opening window, made om clea Pe spex. We de-
cided o eco d all sky da a wi h he window in he open
posi ion, due o he p esence o many abso p ion bands in
Pe spex a in a ed wa eleng hs. A he s a o obse a ions
o a pa icula nigh , he window is opened and a ime is
s a ed. The ins umen is p o ec ed om he elemen s by a
ain de ec o , which i ac i a ed causes he window o close
and he ime o s op. Un o una ely, any da a eco ded a e
he ime o he window closing has o be disca ded. In ensi y
calib a ion o he FTIR is pe o med by eplacing he inpu
mino by a demoun able low b igh ness sou ce.
5Resul s
5.1 Annual Va ia ions in Mesopause Tempe a u e
Figu e 8 shows he imes du ing which OH obse a ions we e
ob ained a Maynoo h du ing 1993. The FTIR ins umen
was unc ional a all imes du ing he yea , and he gaps a e
caused by unsui able wea he condi ions. This igu e is in-
cluded he e as an indica o o he ac ion o ime a ailable
o obse a ions in I eland. An a e age alue o empe a u e
has been calcula ed o each nigh on which da a we e e-
co ded a Maynoo h du ing 1993 and is shown in Fig. 9. The
well-known win e -summe a ia ion o a midla i ude s a-
ion, wi h he minimum in summe and maximum in win e ,
is clea ly e iden in hese da a. The gene ally accep ed ex-
plana ion o his appa en in e sion is ha he cold summe
(wa m win e ) mesopause is main ained h ough adiaba ic
cooling (wa ming) p oduced by a s ong summe - o-win e
me idional cell ha is d i en by b eaking e ically p opa-
ga ing g a i y wa es.23 Also shown in he igu e a e he
empe a u e esul s ob ained by Clancy and Rusch24 om
da a eco ded by he Sola Mesosphe e Explo e (SME) sa -
elli e o an al i ude o 86.5 km a a la i ude o 500N. The
close co espondence be ween he SME esul s and he da a
eco ded in his s udy helps o con i m ha he ins umen
pe o mance and me hods used o calcula e empe a u es a e
eliable. Figu e 9 also shows he p edic ions o he MSISE-90
model25 o an al i ude o 87 km a a la i ude o 53°N. The
model p edic s a mean empe a u e o 1 85.7K,which is some
15 K below ha measu ed in his s udy. Resul s o a ha monic
analysis applied o bo h he model and he measu ed em-
pe a u es a e shown in Table 2 and a e in e y good
ag eemen .
5.2 Combined Resul s om Bo h Ins umen s
I is widely belie ed ha empe a u e luc ua ions a meso-
pause al i udes, which ha e imescales o he o de o minu es
o hou s, a e he esul o e ically p opaga ing acous ic
g a i y wa es om lowe in he a mosphe e.6'7"7 Noxon26
was he i s o sugges ha conclusi e e idence o he pas-
3858 / OPTICAL ENGINEERING / Decembe 1994 / Vol. 33 No. 12
(
Time UT.
(a)
310
290
270
a, 250
230
a.E, 210
190
170
1 5021
200 930926/27
100
i
0
>
-100
-20021 22 23 01234
Time UT.
FPIcompu e
F lRcompu e
Fig. 7 Layou o obse a o y a Maynoo h.
I Con ol oom
MAYNOOTH OPTICAL AERONOMICAL FACILITY
Mon h
Fig. 9 Compa ison o nigh ly a e aged empe a u es measu ed by
he Maynoo h FTIR wi h esul s om Clancy and Rusch24 and p e-
dic ions o MSISE-90 o he Maynoo h s a ion.
sage o an a mosphe ic g a i y wa e could be ob ained by
obse ing simul aneously di e en ai giow emissions o ig-
ma ing om wo di e en al i ude egions. The al i ude o
he peak emission o he OH band27 is cen e ed nea 87 km,
while he 01S emission28 maximizes a 95kmin midla i udes
wi h a small con ibu ion om he he mosphe e nea 250 km.
I mus be ecalled, o cou se, ha hese laye s a e se e al
kilome e s in dep h and ha hese a e he al i udes o he peak
emissions only. Assuming ha he emissions ep esen he
al i udes a he peak o he emission, we can calcula e pa am-
e e s associa ed wi h e ically p opaga ing acous ic g a i y
wa es. Figu e 10 shows empe a u e alues calcula ed om
bo h he OH emission and he 0 S a omic oxygen emission
o he nigh o 27—28 Sep embe 1993. To emphasize he
co ela ion be ween he wo da a se s, he a omic oxygen
esul s, which a e ep esen a i e o he highe al i ude, ha e
been shi ed backwa d in ime by 20 mm. This is he esul
ha one migh expec , assuming ha he empe a u e luc-
ua ion obse ed in bo h emissions is he esul o a wa e
mo ion p opaga ing upwa d om below he mesopause. The
phase lag be ween he wo luc ua ions has been used o
es ima e a e ical eloci y, assuming ha he al i ude di -
e ence be ween he wo laye s is known. A knowledge o
Annual componen Semiannual componen
Mean empiK Ampli ude/K Phase/days Ampli ude(K) Phase/days
OH(3, 1) 200 27±1 95±2 7±1 K .51±9
MSISE-90 185.68 30.1±0.2 95.3±0.6 9±0.2 K -99±1
270
250
230
0
210
0a-E190
Mesopause empe a u es calcula ed om OH(3,1) band
and 01 S(5577) eco ded a Maynoo h Sep embe 27,1993
Time (UT.)
Fig. 10 Combined empe a u e esul s o bo h FPI and FTIR on
nigh o 27—28 Sep embe 1993. The FPI esul s ha e been shi ed
backwa d in ime by 20 mm o illus a e he co espondence be ween
he wo sepa a e da a se s.
he e ical eloci y and he wa e pe iod, which can be ob-
amed om ei he da a se , allows he e ical and ho izon al
wa eleng h o be de e mined.29 These a e impo an pa am-
e e s in de eloping models o g a i y wa e p opaga ion
h ough he mesosphe e.3° Table 3 p esen s a lis o he pa-
ame e s ha we e calcula ed om he wo da a se s eco ded
a Maynoo h on 27—28 Sep embe 1993. The alues o pe iod,
e ical, and ho izon al wa eleng h deduced a e consis en
wi h he summa y o g a i y wa e pa ame e s epo ed by
6Summa y
The Fou ie ans o m spec ome e desc ibed has been used
o make obse a ions on all cloudless nigh s when he moon
is low since Decembe 1992, while he Fab y-Pé o in e -
e ome e has only been used ou inely since July 1993. The
equen ly poo obse ing condi ions in I eland, oge he wi h
a si e al i ude o only 60 m abo e sea le el, make i di icul
o ob ain long sequences o obse a ions. Good-quali y OH
spec a we e eco ded, howe e , wi h an in eg a ion ime o
5mm on 1 14 clea o pa ially clea nigh s du ing 1993. The
Fab y-Pé o in e e ome e is much mo e sensi i e o sca -
e ed ligh and could no be ope a ed nea ly as equen ly as
he FTIR. Ne e heless, we belie e ha he esul s shown in
his pape demons a e he easibili y o ob aining meaning ul
geophysical measu emen s om I eland in spi e o he di -
icul ies usually encoun e ed.
Acknowledgmen s
We acknowledge he con ibu ions o N. E. McKei h in in-
i ia ing his p og am o esea ch a Maynoo h, and o
OPTICAL ENGINEERING I Decembe 1994 I Vol. 33 No. 12 I 3859
Times o OH obse a ions
Jan-Dec 1993 Table 2 Obse ed [OH(3,1) esul s o 1993] and p edic ed
(MSISE-90) mean, annual, and semiannual a ia ions in mesopause
empe a u e a Maynoo h.
12
8
a0; -4EI- -8
-12
Fig. 8 Times a which OH spec a we e eco ded a Maynoo h du -
ing 1993.
Measu ed and modelled mesopause OH empe a u es
Maynoo h, Jan - Dec 1993
Jan Feb Ma Ap May Jun Jul Aug Sep Oc No Dec
Mon h
xX0H13,llMaynoo h1993
M515E90 p edic ions 1 Maynoo h
U Sa eul eda aclancyand Ruoch119991
.OH(3,1)
xIC 1 S (557.7)
IC Xx's x
xxx1*c U
0
(90a.E0I-
250
240
230
220
210
200
190
180
170
I 60
150
140
170
1 50
20 21 22 23 012 3 4
Jan Feb Ma Ap May Jun Jul Aug Sep Oc No Dec
MULLIGAN and NICIEJEWSKI
Table 3 In e nal g a i y wa e
1993, Maynoo h. cha ac e is ics, 27—28 Sep embe
Quan i y Symbol Value
Pe iod 120 mm.
Angula equency m8.7 x 10
Ho izon al wa e speed Vh 155 m 5.1
Ho izon al di ec ion 9-
Ho izon al wa eleng h ),, 1119 km
Ho izon al wa enumbe k5.6 x 1O m1
Ve ical wa eleng h A46 km
Ve ical wa enumbe k1.38 x 1O m-1
Ve ical wa e speed z 6.35 m
Zeni h angle o p opaga ion iy 2.35
Assuming a backg ound wind o ze o m s.
D. Gleeson, M. Ma in, W. Lanigan, and N. Mu phy o
ab ica ing much o he ancilla y appa a us. The help o g ad-
ua e s uden s J. Kea ing, D. Doyle, A. Alcock, D. Ho gan,
J. Galligan, and E. G i in in he de elopmen and es ing o
he ins umen s and obse a o y desc ibed is g a e ully ap-
p ecia ed. This wo k was suppo ed by EOLAS, he I ish
Science and Technology agency, unde g an numbe s RE!
176!89 and SC!91!141. R. J. Niciejewski acknowledges sup-
po om NSF unde g an INT 9312085.
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F ancis J Mulligan ecei ed BSc and
PhD deg ees in expe imen al physics om
S . Pa ick's College, Maynoo h, in 1978
and 1981, espec i ely. He was a lec u e
in physical sciences a he Na ional Ins i-
u e o Highe Educa ion in Dublin om
1981 o 1984. He became a membe o he
acul y a S . Pa ick's College, Maynoo h,
in 1 984, whe e he is cu en ly a senio lec-
u e . D . Mulligan's main esea ch in e -
es s a e in he ields o a mosphe ic sens-
ing and elec on op ics. He has spen pe iods o esea ch a Ci y
College, New Yo k, B ookha en Na ional Labo a o y, and he Uni-
e si y o Michigan. In ecen yea s he has concen a ed on ins u-
men a ion used o g ound-based ae onomical s udies.
Rick J. Niciejewski ecei ed an MSc in
1981 and a PhD in 1987 om he Uni e -
si y o Wes e n On a io in London, Can-
ada. He joined he Space Physics Labo-
a o y o he A mosphe ic, Oceanic, and
Space Science Depa men o he Uni e -
si y o Michigan as a pos doc o al ellow in
1 987, and became an assis an esea ch
scien is in 1990. His cu en esea ch in-
e es s a e in he ield o expe imen al
ae onomy including op ical obse a ions o
he e es ial ai giow and au o a. P ima y opics o in e es a e he
he modynamics and wea he o he e es ial uppe a mosphe e
and he applica ion o s a e-o - he-a echnology o emo e
diagnos ics.