BSTJ 50: 1. January 1971: Measurements of Atmospheric Attenuation on an Earth-Space Path at 90 GHz Using a Sun Tracker. (Wrixon, G.T.)

5.8 MB·English

Measurements of Atmospheric Attenuation
on an Earth-Space Path at 90 GHz
Using a Sun Tracker

By 6." WHIXON,
(aussi seid Noga 3, 180)

Morswremente of 20-Olle ellnsatin dog Whe fla almoephee de
to cbeortin Ing cath, Yop and rain ore presented ond ecmpared with
Svsdlenoons oarsmen ct 46 GH. Th fa one thot vag is th mast
Simperin! contr 9 ahnosphiric exncin at 60 Cla, ght vain
feousingerener Phew <8 alemuation on a number of occasions during
the tmasnremen pie

Atbocption iz the armapheie windaw beoweon the
toorption unl afi en oxygen abeoration Line at 118.75 GEE 3 hue
to abeonption hy the tails of atmosphere oxygrm and. water vapor
feature. Liged water, when preset in the foc 0 esin, emf acd
fg, entice ch aloenol in Ia this atzacepherio window, Mess
treneale of atentation thraih te total atmesphore are af inpoe.
thee it helping fo ces fe “eabicy af eanh-eaelileaomsnut ea
Sons in cis freaueney rion

“Measuremon's of eitenuation through the lear atmagphers 25 a
Imation of clupberie -weter repor enten! have been made by
FT Shimebusure’ on aw ettk-apaoe path ab U0 GH. The resus
te in fais agrecment ith they. A. AW. Stren ard ©. W. Talbert®
he. ©, Hegg tne 1. F, Tutria® bays measure! prypazation Toss
‘ron ere aling goad-basod pts Feauenches
boar $f GH, Their rowlts agne aatistatorly with Uiearetiel pre=
titions prove suits values are saieza forthe pressure broulening
tonsils of the oxpaun mil water-vaper lines# Hogs endl ‘Turia’
Have alsy aeasured atvosation
‘oa pia, and the vaults sgain show reesonely goed aarcement
svt theory!

oo
101 unas sine maemoHe Jovnnady sasuany oT

‘Taore fa however «lack o!experiacotal asa on the effets of ain,
ow nnd fag on attenuation long eurck-spree pas wt freuen
nour 90 Glls. Theoretical tcatment ofthe prebler: is hempered by the
lack af detaited knowlege nf tat ar clout eaaractesstie. Heecnt
papers by AF. Freeny end J.D. Gabbe end RA. Semplakt have
‘Fes runt iba measur He neighborbood of Cr
ford Hill, New Ferwy, gad simian shor patente mes
temenis nf 185 and 2 Gt. Por the mesh part, Rowevee, ile it
Jkvown aoah the hevisontsl and. vertien? dishrtwions of rain, aad
‘ve es ia unread abou those 9 lox

"The netd far dirert monsements of total atmaepheris attention
fn is fregueney ron be Ui apptes- and t-povide the inentioe
Te wary ous eins tensunomeste sorely wei, the Crawford TEN
sam someon?

A rectiver erating st 90 CHa wae serelied atl eaibraedin
the Icboetory. The eon trae noswelly operates ab 18 end 30 GMs,
Fo che purpese of this experiment the GOAGFa weriver vepaned the
SILER feeiver. A Mook digran showing thereover wonneaed to
the som tracker can be seen is Big. 1. Tinea* ar logarithmic char
eur qe weer ava.

"The revives wis rns ls haven douse sideband noise fgnre
| 110 AB fhe, a nog temperature 0° S1W0"R) ard a yeni rege
25 a when overving Uh an,

A ri Tap, cour inn the fine vin a divetioual coupler, was
calibenr! wing mate ond at eno leraperare ane liga nitrogen
tempore

"The sun tasker anlencu Besan wt GHIa wes abserved by allowin
the sun to dif throegh i The rom, 9 emnvolusion of Ube wins
lnigtmnse ditcbution wth the xterm beara pettara,leekad ule
syinmeivie and showed no luge sidelobes. rom thie meaantement
Teauinidta of 25 mineces of ort as eorpted for the tun tracker ek
0 Clg, Aimar ereqeurenen: Never the bagsa wide at 1
GH to bo 8 rainates of ae, Thus, almost the entre slar ds, about
2 minutes of se, wa covered by both Sarme.

"The MOGs reesivor wes eteacked to che sun tracker during the
period from December 2 Yo 16, 1060, During that tine « veriety of
srvceearate ArmEUAMION 108

.

B anaaen :
Srwrasy Eb

ig, lek dsr hs SD.GKE esi the mins.

‘wether wnditons, vil, eleed, shiek fo, rat some wet sn0M,
fecurted ae Crusloal Fill, The extess atensation gt 60 Clie wes
[Egeured fora of thos, No ctempe sce suo to obtain ate ton
ffatistce, In act, one the attenuation through tke clear alsmospbore
Ts heen ategrared sd the close wrather levels noted on the chart
scorer, the receisrr Wie switehed om only sasing pers of bad
sweater op when cla waa present; i other words ovly wen exeese
‘Mention ws eerie

‘heccsion Ss rv ofthe aeration al 00 GH cane! by various
typer of weather mnlitions, To net the neeesurly qualitative do
feviptons for most weuther conditions ‘eg, igh elo, Neary fg,
ler) the excess astennntion of 99 GE ill bo eompaced to Thee
inltaneosty measur wil the 16-C receiver. In this wy the
90-GTle data will be seen less Suto allenation meastzemente
106 rem anc, svrme Taemtest sormsat, raNCAR et

due to rane wonthor earitions, ane more wy rests to be vie
Ju perspective with the moze fariiar 16-GUls date.
Te should bo borne in mind that at the time these measaremente
vwero manda, too son was very low in the eoutnern eky, ie elevation
gle vorying fom about 27° at noon to 18° at @ PM. These angles
forepond to path Ieng:he theovgh the atmasphera of 22 and 40
"uns De pth ength at the reich sesposively

‘ttensetin through the clear atriosphere wee mearuted by obsery-
ing the intanei'y of solar radiation yerus sith angle. Oa a lene cal
Gey {temperature 29° Fy rlative humidity, AE) w valve of O28
AB was cbiained for We allenuatinn through une alsspere

aa Haeess Atanuation due fo Cla

Pour luseelly difeent typea of eloud caver were enceunterod, the
ssvencivion ebartetoreticeo: hich aro ammarsed in able L,ke
Values of atleruation were actully measured ftom be output of Use
Tineneresorder, beemare exalldlbebangce were amore easly measured
hote than oa the output ofthe logavthmic eeordcr. Only those values
of sunution messured between 10 A.M. and 2 PM. aw quoted 'n
3g thase time the almospherie path length took or
values poten 22 end 28 tnses the eeth pally aye The mex'=
‘nurs atrenoition vans quoted in the tele id not acer et the ime
‘the longs path length for any of che four types of eloads cove.

‘The meanied atic” of the Me end 10-CHe cloud alterations
for the fn too cloud eases are about what one would expect based
fon thenrtial ealetations. Feom expeesions given by D. B. Kerr
Tor atiemation deta stpalt water drei iti esi eet Cink
{hie ratio would be 27 for elmde a! 20°C and Ta for clode at O°C.
"The ratio aoanlly metsnted forthe fist two ela ona when the
fread teperwiane was sous 9°C), of aboot 25 is perbaps a Tee
larger than sould he expat steo the cleus temperate is probable
lone 10 0°O, This is all liserepaney howe

‘The laze value of alienation tensed in Civ 8, ie. daring w
period of heary overeast onsen rainfalls, (ae Tip. 2) sees proba
up to the fac thas sineo precisitation oeeured eortly aftarwarde,
these clonds eontained aay lexge water droplets” In this cvent,
‘lenuaios would be greater aan inthe cate of cloude of comparable
‘rarer aontent which a2e no: ceoeiated with preciitaton and whose

Tc catoe ae cntimae a bs aural Lo wii oul 210 perent ie
sper tener aac a ara Ue ale wae
SWEET ME REST
aren
os
srvosnne aeroeeans 7)

dooples size i very mush Jess thm.» waeTength acter yer
fa thue pact of the bess ineereptad se rin; tis would, ofcourse,
also have izerase the attennatia,

(Case 4 ie ifrent trom the proviows throe eases because of (he
lower raceativd rato nf D0 to 10-Clle alieation. Sine the ground
femverafine wa thi Uo fresing doting this measurement the ©
temperatine was prababey belo — 10°C: If the Wouds canis of
cure ie ove onl expres very Te axtamuntion a either Sragueney™
find, indost, Guxing neh of Tis ive, no masnzeable cevensatin
Sus present on cor the @0- or I6-CH ckgamele ia apie a? the
eropletely elndccuvered sky, hiss in togrked contrast to Cate 2
when sn overost aky gave cise wy sovlinuows Mustustions of the
LG sien

‘On x ber of ovensons daring te Cese experiment, however
secne sveantion cil ogeus, dat far which sme ven iv Table L Hom
‘went follows i same cenr thet this atrevtion sas sauce hy elocde
tovteinng superenled ater dope, Such duplets Ive Deen ob=
fered invcloue ot linpearuses as le a8 ANC.

Santon” hae deduced, fru Iboralery measurements, tho dileteie
prperties of supermmisd mater ae —U0°0. TE one eubeietee these
Tilerice poojeries int Ketr'® eaprestinge Jor attenuation die to
fuel sat dive, respecte ali Be to TGC Ha ienatin
tf J e ebtained, Pais agree very ‘avarably with he seared rest:
fof 14 and suggests that cloud of supereceled dcople were indeed
responsibie for the stzenuation expesiaced in Case 4

sa etn Atenuasion duet Fo

Exess atlerution due to Moov Som stex resend an one das,
Dacsasber §. Oa this tisk ciyy abenmncion one 1 load, ra
and for wet meusned. Pigure 2 shows toy ul We logan
recorder onto for Both the W0- and 1h-GTTs chanle for tis daca
‘Also show is tie evar weather sighs nel Th it sen from the Bure
‘thas dasiag the period of honey fog, the siz Metts were much
1g rap than daring ti pend of heavy evens. hie tegen that
te atmngphine wae anceh store ese caring he poise of og. Be
‘even nn an 2 PAI, the ascrage sstenuttior wus 82 eB eC 60
Gls wed 02 0B aL 16 GH, ving a caie of 1.

1 the prevalling. ground temperstae of 134 is taken to be th
bsurbing! Inmperaisee of the ‘water droplets in the fog isnee,
tevpielly, fogs io uot extend very fae above the ground) then from
[Keres ts espeoted raia of $0- to 15s fog sbsorpiun ¥en alae
TO muy wane syereoe eae, JovsNy JaNCnter a

to be ubozt 24. The low messured casio of 16 is probubly du tthe
not thas dang a og the atmorphere ie 100 percent aturaled wit
vator por. Sine the sasio of wtlenuation se 09 and 16 GHs de to
‘eter vepor in che atmoqhere ia abeut 8. at a ground temperature
Of 15°C ita yueeence in fy will lend Go lower predisted ratios af
fttemation besed on emall droplet absorstion aloe.

Irvled, then one esesias she ates fm ee to the exten watar
vapor inthe atnosthere on December au (i, over he ann pre
fat when che clear weather sevel was established! and eubtearta it
but, values of O41 dB and 226 dB ste obtainl fur the averugr
‘ttenustion, ab 0 and 90 Ole respectively, dive to the fog wer
Aroplts alone. ‘Tis gives a value of 28. for tho ratio of 16 (9 90-GH
ctonantion whieh sprees withthe calculatod value of 24

‘28 Lncese Attmuaton due to Rain

Avtonuution due to rain was mouzore on thes days; Doeombrer 8 1,
cond 1 During these cimes, rain 2eies not exceeding I mamy/oar wor
‘measured asing a vain guuge located on Crasford Lil, about 400 fe.
from she min treks,

“Table HT cummeries tho zeeulte ofthe measurements of rain atten
‘dion, In Jig. ) the logesthmie roetd for Deemer 8 a een th
offcet of astonustior due to lish eteacy rai, bebwecr. # end 10 A.M.
fd duo fo interment showers, beeen 10:00) .ML. ad noma,

(On December 10, a Heat e8in war abeerved Fram 1:80 PE vail
2:80 P.M. wien the dyuamic range (25 dB) of the 60-CHs receiver
‘wus execeded, During this time the attenuation, both at 10 end 90
Gils, increaeed stanly betwoen the limite shown in Table TT and the
AB reo af the sctanuaticn, fnctuming rendouy between 25 and 29,
thud an average reine 0? ato

"T. 8. Chu! ha caleu'ated expete ein ellemantions for dierent
sin ratan using a Taws-Parsone drop wie citation, Prom Cha’
‘work i ie aber Ui sce exif) ate verse, the enti ot
alemation sl §0 and 16 GH doureaes. Tie eon be oun ia Tis,
‘shore the rei apo: agains rain ot. The dsrase ea he unde
owt by fist waliyg Cha TaxeseParsons divellion Gwe ©
Chu srl Haz) the average ently size inaremor with increasing
rain rate, Now for each feequerey there iw ecrain drop sito whieh

‘most efetive in absorbing elostromagnoti relintion™; the higher
he frequency, ihe exnller the moet efleetive raindrop wine, Ae I
Gifs tho mast nhuncont raindzope havea smalls cae then Ue mh
sce moe: efeebive; consequently, the increasing cze in a heavier rit
a

RRRERSTERE KORVER MIR a0 KAPRRAE—TT TEV,
vill mersase tho abcommdon effoorvenese, Ab 90 GFE hawaver, che
‘mort abundant doops are already langer than those whieh are most
‘eeetive; conzcqueniy, tae ineeasing sizo in x buuvlor rin will de-
feast effectiveaesns© The tet reeule is to dosrone the cai 0°
A0-to KEGHs iain etlamiation ce the tan Tate ieresace

‘The obsueved ratio of 27 on December 10 incites (ate ig 3) thal
stenuation due toa very light rain was boing mensure. 2 i interes
Ing ta nore that oven tkong the G-GLLz attaantion inerecace dras-
tealy during the meaeurng period, tae ratio remained rowsonehly
constant. Ths suggeis thet the inerezsod stzenuction Was et enuse
hy inetasing’s hesvy main‘all a: one pring fut by ke stanly
inereasing eecuteenes of light rin along the becm pth taroagh the
linosphere

Gn Devember 14 the allemation through rain mixed with snow,
rove yall ning evan, aes bere, The retin of C918. 0H
iiemetion Sows 2 definite ‘nd, bogioting al a valne af 2%
Alnevasing, to 17 and increasing again se the rain sloppal to about,
2, The maximum valve of OMGH2 attenuation (36 oR) cil no,
focus te samp Hime as che masinanm eave a 18GB aenntion
(07 dB). Tho Inve genre wile te ratio wi ab ite minim ef
7 nnd abot 10 minates afar ho maxon attenbation nt 99 Cds
sas revi, It the eet of the mow it neglected, che abave reste
can be satorpzetec sing Ie. J, e8 indicating an Snereasing Fain rate