Radio and radar astronomical studies on lunar and planetary ionospheres and atmospheres, and solar activit

Eshleman, V. R.

English

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RBDIOSGZEXCE IAJ34XA- 
S T A N F O R D  U N f V E R S I T Y  
Stanford, Call iiornia 
January 2966 
, 
Semi-Annual Status Report no. 6 
for the period 1 July - 31 December 1965 
Research -ant no, N8C-m 
SEL mject noe 908 
v, E. Eshlernan 
ProQect Director 
N66 -1952 8 
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CATEGORY) 
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4 Rsearch conducted in whole or In part Under M A  Grant no. TT( 
* 
Jtncludes theoret2Cal and exper ipenta l  radio and radar studfes  et lunar 
and planetary ionospheres, atatO6phere8, and surfaces, and radar s tudies  
of the 8un and interplanetary medZum. 
Cislunar @18 Studies - 
A preliminary note published in the a1 of GqophysScai Reso- 
for September 1, 1963 (a lso  fssued as Scf. -Rpt,- no. 8 on this contract) 
described an experimental radar technique for moasurZng digferentdal 
group delay to an accuracy of 10 psec and presented results of Slve  
measurements. Since that t fme,  the 29 and 50 Me radars have been aod i f l ed  
to improve power output and time resolution and, durfng the months of July 
and August, were used to deterishe cislunar electron content on 60 con- 
eecutfve lunar merfdian tranafte. 
Ionospheric electron contents, dctenained by the  Faraday rotation 
nethod on signals from Syncom IbSf, were subtracted from each radar deter- 
mfnaftian of total content, The results of th i s  experiment reinfoxwe the 
earlier conclusfon that there are two dif3ttince r-ons beyond the fom-  
sphePe. 
the sm, the average cfslunar electron d0nsftp beyond the fcrmspbere fs 
8pppoxriSmntely 175 f 50 am-3. 
most of the radar path is beyond the shock wave boundary, &he average 
density beyond the fonosphere is 50 
to change on a day-to-day bnsfs ~ h f 3 . e  t h e  shape and direction are  cliffei-on't; 
from month to month. 
WAthin the solar wind wake of' the earth, Pn the quadrant opposize 
In the general direction of the sun, w?mrct 
50 ~ r n r ' ~ .  The wake density oppaars 
3nVest2gatiOn might prove fruitful, ft Bs felt that these two dlfforent 
Xn adci5tion 90 the cfsluna~ eonlent anrilfrsis, reduotion of the chirp 
returns f m  the et;mdpoint of lunar surface chammteriStic9 hras cantfnued. 
sweep8 at  aboat 25 ahd 50 m. 
d g n d  hnwbg %he 881110 frequency-time variation, whfch resulted in targets 
The re;Plected sfgnals vere mixed w5th a 
of d4f f erent ranges shOw3ng difOeri3nk Prequendos (conatant for Statfonary 
tazgets), Tha heart oe the reduction is, therefore, a s p e c t ~ n t  analysis 
J 
power spectral densfty to 2 Fie. 
2 
i 
f 
* 
Both Che change in range and the rangemte (Doppler) of the moon 
cause the frequency cori*qondinq do 8 particular range fneerod an 
%he soon to  ebrange. ThSs cbrurge is Insjlgr~lficzni: cmp-ed to the window 
during One retarn, Bu$ 3sfl oldor t o  average many minutes wrtb of retams 
together, f t  necessary to r~prove (reverse) tAe change. Fortunately, 
MS is easily done since i t  fa vepy closely parabolic f n  shape durfng 
the periods new -it *ea the records, are made. 
W h f b  the spectra of the individual 2.5 8w reeozds are considerably 
afferent frm each other, even when they 81'8 adjscent and show several 
peaks, fl mhtivelg smooth curve can be obtsdned by superfmg~sing many of 
them. Bscaaee tbe sSgnal-to-aoise ratio isn'.t: suffdcrently high, only the 
first 400 to 600 p e e  of the 11,600 wsec total delay f -  &bm the front to 
the l i m b  can be seen in these  coapasites. 
that tho ecbb changes most rapidly wfth  range and the high ~esoXutfon 
obtafnable using these techn5ques 2s most usoful.. 
However, it is in th3s reglon . 
Besfdw camputing the average for esch rango interval over many 2,5 
SeC reCord8, the variance and correletion coef flcfen-ks with neighboring 
rango intaruds were also obtained. 
sbottt the mean t o  the mean for each rage iocrsased f i - ~ ~ i l  abox'c 0,b .Pur 
Pange Sntarttds not fnczuding the 11?(3on to 0.6 - 0,7 for  those near the 
peak of echo atsengch on go lMHB and from aMut 0-2 to Od!. 
The plots of fl/mm.n v5. range and varfance VO. range are very s f m i l a 2  Eo 
those of ~ 0 a n  vs. range. 
T ~ s  ratio sf the K%S fXucOuaGion 
0,8 oil 23 &GE~ 
The nature of the reflection of this kind of sigrral is not yet well 
pulses. 
5s 
3 
Work 1s continufng on bfstatic-m&r nethods for the study and mapping 
of planetary surfaces. 
construct the radar brightnesss dietributlan of a planetary surface f r o m  
the interference pattern formed by the direct, and reflected, rays when 
the surface fs illmfnalod wtth radio frequencies from the earth. 
reports deecribe the138 technlquffs in detail .  
Thus far we have shown that f t  i a  possible to re- 
Previous 
Experhtental verification of the pPedicted response functfon has been 
obts3ned by ol;rt;fcal simulntfon and further sfmdies In this man are con- 
tinuing. 
A theuret5cdt invos$iga.-tion of the effects 02 varfous nurfrrce parameters 
ha0 bean star- bu" so Par t h i s  subjecl 5s no2 mell  understood, 
concamaftant w5th *he design of optinnnu Filters for mapping application. 
This is 
Planetary Atmospheres 
The 8tsniord study of tho $!;tarlnep N occultation data has in part been 
fundod through RsG-377. 
efSE5c Report, fesuod dofntlg by NsClm ( 
The results of t h i s  work are presented in a Bcisn- 
no. 5) End MAsn contract 
N G y Y p m - *  (Bel. n i t .  no.. 2). 
fn adtiltion, o atuciy of the prablems related to conduakbg a rad50 
reportfng perfod, Wh310 the Martian a-ospbere was so tenuous that it 
reciuired high pm9afon rnemui*ements to  det@ct; its effects on radio sfgnals, 
the wherean atmosphere nay actually be so dense that no radio Slgnal can 
psnetpste along u path bngentfd to the surface of Venns, These and other 
5 
Baalcslly the scheme 2s one of analog cqding under an averago power 
constraint Pav. A .code book 02 H messages is un3f'ormly apread the 
Pnterval (0 ,  1) on the real l ine .  'ib send message ma, the 'craasmttter 
sen& an tmplftade proportional to the position in (0, 1) of mi. The 
receiver Calculaees f t s  rntl.9fmum likelfhood estimate of and sends it 
baek to t E e  t r d t t e r .  The transmitter then transmits correction data 
to the rece3ver, which then sends back h new sstfmnte of t k ~  mocsage 
'phis iterative procress is continued €l 
m2 
mi 
times for sah message transmitted. 
is determined by the required probabflfty of error Pe for the opera- 
ting rate of transolll@s%on R, bandwidth W, and signal-to-nolse rat90 
€ m e  
Belng of particular fn%smst,  the bandl5rnlt;ed clinnnrl was studiod, As 
oOigjlnalP3 derfwscjt, the coding sebsme achieved c'nannsl capacity C 
I-t, i,e,, w2tR an unlfmited number of messages W and iEorat5ons N. 
'Ib be practical, 
that favorable sftuations do d s t ,  
Sn the 
N must be mall, @,a;., 10 or 20 at  mast. I t  was found 
A series of graphs has been constructed 
6 
- 
to ahow the poPsfbh3 mode61 of op8Pcnfion and the  resaltant Pe ond 19 for 
spec3fietI sJrstem psrametera H, SfI$, and relatfve transmiasfon race R f C .  
For 16 - < lodo sn8 Sp”a 2 0 db, i t  $8 possible to achieve error proba- 
bilPtiea P e s  low6 and re1att;fve rates R I C Z  0.5 d t h  N S  20, Operation 
far 8/” < 0 db h~ posePble under increased N. 
The Smportant conclusion of the etudy wa8 that, theoPetfcallg, the 
coaSng tcbme can opepate under a sfcable code book end a few iterations 
and 89%21 amhieve low prdbab2lfty of error and high transmlesion rate. 
d n s  to t e a l s e e  the  system; work vi11 continue fn th3s arear 
most difffcult probleprs n r i l l  be ririakm.lcatfon of the  system performance 
degradtation under non-ideal signal waveforms snd receiver equigtnent and 
the 8c-dation of foap delay. 
It  
The two 
PTasma Bffecta on. Space 
Zt ~ U B  been pmpoeed that dfurnd vnrlntions in t he  fondsphere cause 
si@ffcant errors in the tmckfng of space probes such as Mariner IV. 
lb teat thfS hypotheds a computer program usfng changfng ionospheric 
C O x I & t i O ~  and spwe probe p o s i t h n s  as parameters has been written. 
grog?am plots graphs of expected eloolron content and Doppler sh f f t  09. tfne. 
The typical ionospher5c Doppler shift of bIsr;riner Df’a telemetry segnd 
This 
(tlm-lmy lock) (24 sac) is f: 0 . 0 ~  -3 m a f w r m  of 6.06: c-,s merngea 
over the day. 
along the ray path of 9 x 109 mel;ers/sec, %lese d = i t ~  are a180 being 
analysed fmn %be, standpo-in$ of orbit predtct9on and trajectory detewina- 
tion. 
2 % ~  corresponds to an average ve locf ty  error conponent 
7 
* -  I 
X t  wa8 diecovered while plottfng one-oeeond Doppler frequency 
rerriduale from Baariaer XV that *he primary source of short-term ermr 
fs e8uaed by the receiving sy8tsarta countfng only zero crossings of the 
r e C e l w e d  Sf-0 
tbis 8-r VBPB Pnvestdgated. 
MothodS of &@tal B f f t d n g  and smoothing ta minimize 
Z t  ib hoped that by autocorrelating the one-second DoppXer data frum 
W n e F  fv, electron 8treari1~ and Iwnchfng em be detected and ranged, An 
antoCorrcSation grogpan has been writ ten and debugged. 
were hampered I@ the EQTO crassing noise  mentioned above, Smprovsd Mafiner 
Fl data fPoa the Jet Pmpu2aion fiaboratory is now being awa5ted. An 
&ddftional opporttmif;g 13or nutocarrelstion Studfes nay occur when the 
efgnd ray paa pssoes near the sun fn   arch, 
I ~ t i a I  trial  runs 
Receiver CpMtructfion Techniques 
A c#mparfeon and campflation of the advantages and Lfmftatfono of efght 
mlcrominirturicstfon fabrication proecssee has been complelod. 
wxm @ven to amtorn linear circuit deolgn 
linear deroaircu5ts,  and included the follovzing ~ Q P ~ C S :  
range of passive elenents, cost, ease 0% design, rel iabi l i ty ,  radfcl'cfon 
inimuaty, parer capab9lity, snd afze and might. 
tF88 obtained fPom a seareh of %;be Ifteraturo pu'nlished during the pmiod 
1963 thraugh 19@, fram lecture@ attended at bath Stanford Universitp and 
the 1963 Vqscon Show, and %ram personal interviews with several repre- 
sentatives of the rn9c~~cProu5ts 3ndust;rg. 
Consfcisration 
well as Cfs3Q3n ~ 5 t h  nvallnb'le 
frequency capability, 
Thts 92vage cmrxtry 
8 
.. U 
tion Charts. During the summer this Cook the form of a cormaafieial product 
mfcroarfnfatuPfcatfon feasibility study at GPanger Assacfatee, palo A l t o .  
The steps Snoludedt 
Numerfcal priorities were then used to weight the relevant differences 
thie technfme, a sign5ficant ciinngo 2n one of tho differences, OF a change 
9 
. 
Spira. P. Me. D i g i t a l  Yeasurment of Mf fa raa t i a l  Time Delay of Pseudo Rand- 
coded Sibal;, S c l .  Rpte no, 6, Ns6m, S U - S E I ~ ~  
Laboratories, Stanford, California, Janriary +- 1 , Stanford Electronics 
W, S., Bfstatic-Radar Measurements of Interplanetary CoXlisionless Bhock 
NSG-m, Tech. Rpt. no. $06 -2, ra--=5(83) , 
Bleotronics Laboratories, Llt~ntard, California, 
October 
SchstkniJk, J. P. M., Coding Scheaos for  Additive Noise Channels with Feedback, 
Scf. Rpt . no. 10, PPsbm, SU-SEG65-073, Stanford Electronics Laboratories, 
Stmford, Cdifornia, August 1965. 
YOh, P., 8 b  T. Howard, B. B. LuSignan, m d  V. R. EshLemCan, bnmr Radar Measure- 
ments of t h e  Earth’s Hagnetosplieric Wake, Sci. Rpt. no. 11, N S G - ~ V ,  
SU-SEI&-085, Stanford Electronics Lalooratories, Stanford, Cnlifornin, 
August 1965. 
. 
Yoh, P., Bndnr Studies of the Clslunnr Medim, Scl. Rpt.  no. 12, NsG-Jfl, 
Sa-SEL-65-091, StanFord Electronics Laboratories, Stanford, Cdifornfa, 
December le. 
TyIor, 0. L., me Biatat ic  Continuous-Wave Radar Method €or t h e  Stcdy of 
Plnnetary Surfaces, 
Electronics lnboratories,  Stanford, California,  October 1965. 
Sei. Rpt. no. 13, NsG-377, SU-SEL-~-W~,  Stanford 
Hoh, P., Immr Radar B?ftsuremeats of the Diurnal Excliange of lonizcrtion between 
the Ionosphere and the Magnetosphere, Sci. Rpt, no. 3.3, Ns0-577, 80-SEL-65-103, 
Stanford Eleatronics &&oratorios, Stanford, Californin, December 1965. 
Howard, E. T., V. R, Eshlemran, 0. H. Barry, and R. B. Penaick, Rndnr measure- 
ments of the t o t d  cislunar electron content, J, Gzophgs. R e s . ,  E, 4357- 
4363, 1967. 
Kliore, A., D. L. Cain,  G. S. Levy, V. R. Eshlemn, G. Pjeldbo, and F. D. Drake, 
Occultation experiment: 
atmosphere and ionosphere, Science, M, 1243-1248, 1963 
results  of the first direct measurement of X m s ’ s  
YOh, P., 8. T, Howard, B. E. Lvsignsn, and V. H.  Eshisaca, kzzr  r.r?ar monsure- 
ments 04 the earth’s magnetospheric wake, J. Oeophys. R e s . ,  E, 189-19b, 
1966. 
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Research at the Stanford Center for Radar Astronomy Semiannual status report no. 6, 1 Jul. - 31 Dec. 1965

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