Impedance, resonance, capacitance, electrostatic, and Langmuir probe performance for ionospheric electron density profil

Fejer, J. A.

Heikkila, W. J.

Holt, O.

English

NASA Technical Reports Server

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I I 
1. I’ 1 
QUARTERLY STATUS REPORT NO. 5 i 
// FOR THE PERIOD AUGUST 1, 1965 THROUGH OCTOBER 31, 1965 
NASA CONTRACT NSR 44-004-017 1 
COMPARISON OF ROCKET-BORNE PROBES FOR 
ELECTRON DENSITY MEASUREMENTS 
J. A. FEJER, W. J .  HEIKKILA, 0. HOLT 
PRINCIPAL INVESTIGATORS 
-. 
* * * * * * e * * * * * * * * *  
Construct ion and t e s t i n g  o f  a l l  t h ree  f l i g h t  u n i t s  was completed on schedule,  
and t h e  f i n a l  checkout and t e s t  o f  each f l i g h t  u n i t  was made a t  t h e  Goddard 
Space F l i g h t  Center from August 18 through August 27, 1965. The rocke t s  were 
launched on schedule;  NASA 14.213UA was launched on August 31, 1965, and 
NASA 1 4 . 2 1 4 U A  was launched on September 1, 1965. 
14.76, was no t  launched. 
The backup rocket ,  NASA 
NASA 14.213UA was a success fu l  f l i g h t  wi th  t h e  only f a i l u r e  being t h e  breaking 
off  o f  t h e  20 f t .  antennas as they  unreeled from t h e  rocket .  
instrument from CRPL (Central Radio Propagation Laboratory, Boulder, Colorado) 
d id  rece’ive good d a t a  be fo re  t h e  antennas broke, 
t h e  f l i g h t  i nd ica t ed  no o t h e r  e l e c t r i c a l  or mechanical f a i l u r e ,  and with t h e  
except ion of t h e  antennas,  a l l  experiments performed s a t i s f a c t o r i l y .  
However, t h e  J 
Telemetry received dining 
NASA 14.214UA had a major f a i l u r e  i n  the  clamshel l  system; the  clamshel l  failed 
t o  deploy a t  t h e  scheduled time, 
experiments using probes housed within t h e  clamshel l .  
ceived from t h e  CRPL experiment u s i n g  t h e  20 f t .  antennas before  they broke 
off  dur ing  deployment. 
Therefore,  no d a t a  was received from those 
However, da t a  was re- 
The backup payload t o  be launched on NASA 14.76 was re turned  t o  t h e  Graduate 
Research Center  t o  await f u r t h e r  d a t a  analysis and t o  make necessary design 
changes. Before launching NASA 14.76 t h e  following s t e p s  a r e  being planned: 
(1) redes ign  of t h e  CRPL antenna system, (2) r eva lua te  t h e  clamshel l  design 
both e l e c t r i c a l l y  and mechanically,  and test  f o r  cause of  f a i l u r e ,  and (3) 
make any necessary instrument design changes which are ind ica t ed  by t h e  d a t a  
received from t h e  two previous f l i g h t s .  Telemetry received during t h e  f l i g h t  
i n d i c a t e d  a l l  instruments functioned properly throughout t he  complete f l i g h t .  
The f i r i n g  d a t a  f o r  NASA 14.76 has been t e n t a t i v e l y  set f o r  t h e  f i r s t  q u a r t e r  
o f  1966. 
s GPO P R I C !  .N66  0. IACCESSIO?~ 19186 NUMBER) ITHRU) 
https://ntrs.nasa.gov/search.jsp?R=19660009897 2020-03-16T23:22:34+00:00Z
’ . .  
REPORT ON A I1ULTIPLE IONOSPIIERIC PROBE ROCKET EXPERIMENT 
W. J .  H e i k k i l a  
NASA Contract  No. 44-004-017 
Second Conference on Direc t  Aeronomic 
bleasurements i n  t h e  Lower Ionosphere 
Urbana, I l l i n o i s ,  September 26-30, 1965 
SOUTliIJEST CENTER FOR ADVANCED STUDIES 
1’. 0 .  Box 30365, Dal las ,  Texas 75230 
A Division of 
GRADUATE RESEARCfI CENTER OF TllE SOUTlIlJEST 
I .  
. .  
REPORT ON A MULTIPLE IONOSP11EKIC PROBE ROCKET EXPERINENT 
\.Jhile r ad io  wave propagation methods have cons iderable  merit i n  
ionospheric  s t u d i e s ,  neve r the l e s s ,  it is o f t en  found d e s i r a b l e  o r  necessary 
t o  use  probe methods f o r  l oca l  measurements near  the  rocket  o r  s a t e l l i t e ,  
This  need arises p a r t l y  out  of the presence of space-time v a r i a t i o n s  i n  
the  e l e c t r o n  concentrat ion.  
t o  e r r o r  due t o  t h e  i n t e r a c t i o n  between the  probe and the  ionospheric  plasma. 
A program f o r  t h e  c a r e f u l  eva lua t ion  and comparison of d i f f e r e n t  probe 
techniques has ,  t h e r e f o r e ,  been undertaken. 
philosopliy t h a t  t he  ionosphere provides t h e  b e s t  poss ib l e  plasma labora tory ,  
and t h e  seve ra l  probes have, t he re fo re ,  been instrumented i n t o  a rocket  pay- 
load. Each payload, c a l l e d  a t tMult iple  Ionospheric Probe" inc ludes  f i v e  
d i f f e r e n t  types  of  probes f o r  e l ec t ron  dens i ty  measurements, four  o f  t hese  
being instrumented by the  Southwest Center f o r  Advanced S tud ie s ,  Dal las ,  Texas, 
and one by t h e  Cent ra l  Radio Propagation Laboratory,  Boulder, Colorado. ine 
experiments are l i s t e d  on the  f irst  s l i d e .  
Unfortunately,  many probe methods a r e  sub jec t  
This  program i s  based on t h e  
-.. 
The f i r s t  o f  t hese  instruments  i s  t h e  "Resonance Relaxation Probe", a 
low-power r ada r  sweepiriy t h e  freqiiencj. range frm 1.0 down tn 0.1 ?lHz i n  0.5 
seconds; it i s  designed t o  de t ec t  slowly decaying plasma o s c i l l a t i o n s  of t h e  
types  observed with t h e  Alouet te  and T o p y  s a t e l l i t e s .  Such plasma resonances 
occur  n e a r  t h e  plasma frequency uN, t h e  e l e c t r o n  cyc lo t ron  frequency ufl and 
i ts  harmonics, and the  upper hybrid frequency uT = /-. P a r t i c u l a r  
o b j e c t i v e s  were t h e  measurement of t he  i n t e n s i t y  o f  t he  resonances as a 
func t ion  o f  e l e c t r o n  concentrat ion,  c o l l i s i o n  frequency, and length  o f  
antenna.  This  experiment was a l so  included i n  the payload f o r  t h e  purpose 
o f  provid ing  a c a l i b r a t i o n  f o r  the o t h e r  probes,  s i n c e  t h i s  probe is  no t  
. .  
2 
as l i k e l y  t o  be inf luenced by sheath e f f e c t s .  
by \J. Calver t  and J. Iiugi11 of CRPL. 
This probe was instrumented 
A second instrument ,  t h e  Variable Frequency Impedance Probe, was 
designed by J. A. Fe je r  and K .  Tipple  t o  measure t h e  r e a l  and imaginary 
p a r t s  of t he  impedance o f  an11.6 cm diameter  sphere.  
designed t o  show t h e  na tu re  of t h i s  impedance over a broad frequency range 
(3 .0  t o  0.1 PtIIz) on e i t h e r  s i d e  of t he  plasma frequency. 
The experiment was 
The t h i r d  instrument ,  a l s o  due t o  J .  Fe je r  and K .  Tipple ,  i s  t h e  
"Resonance R e c t i f i c a t i o n  Probe", s i m i l a r  t o  probes f i r s t  used by Japanese 
workers. 
sphere,  while  t h e  swept frequency RI; vo i tage  i s  appiieci. 
f l o a t i n g  p o t e n t i a l  o f  such a probe shows. a resonant  maximum near  a c e r t a i n  
frequency. 
f r e q ~ ~ n c y ,  h-& recent  theoretical cons idera t ions  i n d i c a t e  t h a t  t h e  maximum 
occurs  below t h e  plasma frequency, 
t h i s  theory.  
This  probe measures t h e  f l o a t i n g  DC p o t e n t i a l  o f  t he  same 11.6 cm 
The nega t ive  
I t  was a t  f irst  thought t h a t  t h i s  frequency i s  the  plasma 
The experiment provides  f o r  a t e s t  of  
The fou r th  instrument ,  designed by W. J. I f e ikk i l a  and N .  Eaker, i s  a 
capac i tance  probe opera t ing  a t  a frequency well above t h e  plasma frequency; 
i n  t h i s  case, two sepa ra t e  f requencies  
1 l . b  cm sphere is  used on a timc shared b a s i s  w i t h  t h e  previous experiments. 
This  sphe r i ca l  c a p a c i t o r  s e rves  as t h e  tun ing  element i n  an o s c i l l a t o r  c i r c u i t ,  
t h e  o s c i l l a t o r  frequency being then a convenient measure of  t h e  d i e l e c t r i c  
cons tan t  of  t h e  plasma. In  t h e  absence of  ion  shea th  e f f e c t s ,  a change i n  
o s c i l l a t o r  frequency would be d i r e c t l y  propor t iona l  t o  a change i n  e l e c t r o n  
concent ra t ion ;  however, t he  ion  sheath effects are s i g n i f i c a n t  and d i f f i c u l t  
i n  t u rn ,5  and 10 Miz.  The same 
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t o  eva lua te .  The primary purpose of t h i s  experiment i s  t o  eva lua te  t h e  
ion shea th  e f f e c t  q u a n t i t a t i v e l y ,  making use of t h e  accura te  determinat ion 
of e l e c t r o n  concent ra t ion  provided by t h e  resonance r e l axa t ion  probe, 
The f i f t h ,  and f i n a l  type of experiment i n  t h e  payload, again due 
t o  1J. J .  I i e i k k i l a  and N.  Eaker, i s  a DC probe. Two d i f f e r e n t  instruments 
were included; one, t h e  so-ca l led  " E l e c t r o s t a t i c  Probe" measured t h e  ion 
cu r ren t  t o  t h e  large sphere,  while t h e  o t h e r  was a conventional Langmuir 
Probe, us ing  both a s p h e r i c a l ,  and a c y l i n d r i c a l  c o l l e c t o r  i n  tu rn ,  
measurements were intended t o  t e s t  e l e c t r o s t a t i c  probe opera t ion ,  and t o  
measure t h e  veh ic l e  p o t e n t i a l  , 
These 
The d i f f e r e n t  experiments were programmed t o  opera te  on a time-shared 
b a s i s  i n  o rde r  t o  avoid mutual i n t e r f e rence ,  A t o t a l  o f  e igh t  te lemet ry  
channels were u t i l i z e d ,  inc luding  one with a bandwidth o f  10 K I I z .  
F igure 2 is a t y p i c a i  por t ion  or' iiio I ' i ig l i t  i - e c ~ r d ,  obtaincd at  a: 
Three d i f f e r e n t  modes of  opera t ion  are shown a l t i t u d e  of 146 ki lometers .  
l abe led  Periods IIB and IIIU of  Frame No. 46 and Period IA of  Frame No. 47. 
C!r?ly f ~ u r  of t h e  t e lemet ry  channels are  shown, During Period I ,  channel 11 
of  t h e  te lemet ry  c a r r i e d  t h e  A-scan f o r  t h e  resonance r e l axa t ion  experiment 
as shown on t h e  r i g h t  hand s i d e  o f  t h e  s l i d e .  
is swept from 3.0 bl€tz down t o  0.1 Fltiz i n  about 1 / 2  second. 
a t  t h e  extreme beginning and end of  t h i s  sweep a r e  ins t rumenta l  and should 
be ignored. During t h e  a c t u a l  sweep s e v e r a l  resonances are apparent ,  in-  
c luding  t h e  one a t  t h e  e l e c t r o n  cyclotron frequency, one a t  t h e  plasma 
frequency,  one a t  t h e  upper hybrid frequency, and one a t  t h e  second harmonic 
o f  t h e  cyclotron frequency. 
In  t h i s  scan,  t h e  frequency 
The responses 
A t  times, t h e  resonances a r e  broad and poorly 
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4 
formed; a t  o the r  times, they are clean and symmetrical. 
t h a t  ionospheric  r e f l e c t i o n s  a r e  present ;  t h e s e  cannot be resolved on 
t h i s  presenta t ion .  In  genera l ,  the resonances occur a t  t he  expected 
frequencies  and with t h e  expected r e l a t i o n s h i p s  throughout t h e  f l i g h t ,  
s o  t h a t  i d e n t i f i c a t i o n  o f  t h e  resonances i s  reasonably conclusive.  
Channels 12CN and lOCW c a r r i e d  information on t h e  impedance of  t h e  antennas. 
Unfortunately,  p a r t s  of t h e  antennas broke o f f  and only weak responses on 
t h e  impedance channels were obtained. Channel 8CW c a r r i e d  Langmuir Probe 
s e n s i t i v i t y  range information during Period I ,  t h e  main Langmuir probe d a t a  
being c a r r i e d  on another  telemetry channel riot shown on t h i s  s l i d e .  
I t  i s  poss ib l e  
[luring Period 11, t h e  t r a n s m i t t e r  f o r  t h e  resonance r e l axa t ion  exper i -  
ment was turned  o f f ,  but t h e  r ece ive r  was l e f t  on with i t s  output  on Channel 
I I .  A t  t h i s  time, it was rece iv ing  a s igna l  from the  va r i ab le  frequency 
impedance and resonance r e c t i f i c a t i o n  probes,  whose outputs  are c a r r i e d  on 
t h e  next t h r e e  channels.  
smooth frequency dependence i n  the  absence o f  t h e  plasma; i n  t h e  ionosphere,  
however, t h i s  s i g n a l  was reduced considerably a t  s eve ra l  d i s t i n c t  f requencies .  
Four of these  resonances could be i d e n t i f i e d  as being the  same resonances as 
shown during Period I ;  namely, wII, uN, uT, and 2u1,. 
were observed f a i r l y  c o n s i s t e n t l y  throughout t h e  f l i g h t ,  one near  t h e  cyclo- 
t r o n  frequency, and one nea r  t h e  plasma frequency. 
n o t  y e t  been i d e n t i f i e d .  
The r ece ive r  output  showed a s t rong  s i g n a l  with a 
Two o t h e r  resonances 
These two resonances have 
The impedance of t he  sphere d id  show a resonant  behavior  a t  a frequency 
which was i n  genera l  not  t h e  plasma frequency. IVhen t h e  plasma frequency was 
apprec iab ly  g r e a t e r  than t h e  cyclotron frequency, as i n  t h e  case  shown, t h e  
5 
resonance occurred a t  a frequency below t h e  plasma frequency. When t h e  
plasma frequency decreased below the  cyc lo t ron  frequency, t h e  resonance 
remained above t h e  cyc lo t ron  frequency. 
c o n t r o l l e d  by some combination of  t h e  cyc lo t ron  and plasma f requencies  , 
such as perhaps t h e  hybr id  frequency. 
This resonance appeared t o  be 
The sphere  p o t e n t i a l  was telemetered on Channel 8 CW. During much 
of t h e  f l i g h t  t h e  apparent p o t e n t i a l  was o f f - sca l e  i n d i c a t i n g  t h a t  t h e  
veh ic l e  p o t e n t i a l  was more negative than  had been a n t i c i p a t e d ,  i n  excess 
o f  0.5 v o l t s .  For t h i s  reason, no r e c t i f i c a t i o n  effect  i s  ind ica t ed  
dur ing  t h i s  sweep, but t h e  next  s l i d e  shows such an effect ,  f o r  Frame No, 
7111)  a t  i; altitude of 14c. km. dur ing  descent .  The evidence is  conclusive 
t h a t  t h e  resonance r e c t i f i c a t i o n  does not  occur a t  t h e  plasma frequency. 
To t h i s  e x t e n t ,  t h e  theory  mentioned e a r l i e r  was cor robora ted ;  however, 
t h e  theo ry  d i d  not  take t h e  e f f e c t  o f  t h e  magnetic f i e l d  i n t o  account 
and t h e  r e s u l t s  show c l e a r l y  t h a t  t h e  magnetic f i e l d  inf luence  i s  s t rong .  
During Period 3 ,  t h e  sphere was switched t o  t h e  high frequency 
capac i tance  probe experiment, During t h i s  per iod ,  a complex b i a s  program 
was played on t h e  sphere ,  cons i s t ing  o f  a swept po r t ion ,  s i x  d i f f e r e n t  
s t e p s  ranging from -250 v o l t s  t o  -1 v o l t  a l t e r n a t e d  with +1.4 v o l t s  and 
f i n a l l y ,  four  broader s t e p s  o f  1.4 v o l t s  and -100 v o l t s ,  Throughout 
t h i s  time, t h e  probe o s c i l l a t o r  frequency was measured by means of a 
d i s c r i m i n a t o r ,  with t h e  d a t a  c a r r i e d  on Channel 11. 
a l s o  determined by a counting technique dur ing  fou r  32 ms. i n t e r v a l s  
J u r i n g  t h e  l a t t e r  h a l f  o f  t h e  b i a s  program, wi th  a d i g i t a l l y  coded r e s u l t  
r ead  i n  fou r  s h o r t  b u r s t s  as shown, 
w h i l e  t h e  swept b i a s  was appl ied  i n  t h e  example shown; i t  was appl ied  on 
The frequency was 
The IiF e x c i t a t i o n  was n o t  appl ied  
, 
6 
a l t e r n a t e  frames. 
capacitarice with +1.4  v o l t s  appl ied r e l a t i v e  t o  the  rocket  body. 
The tops  of the pedes t a l s  are a measure o f  t h e  sphere 
Under 
t h i s  condi t ion ,  it may be assumed t h a t  t h e  l a r g e  sphere was only s l i g h t l y  
nega t ive  with r e spec t  t o  t h e  plasma. The ramp s t e p s  i n d i c a t e  t h e  dependence 
of t he  capac i ty  on (negat ive)  sphere p o t e n t i a l .  The measured capaci tance 
as a funct ion o f  p o t e n t i a l  will permit a complete eva lua t ion  of  t h e  ion 
shea th  behavior as a func t ion  o f  probe p o t e n t i a l .  
Channels 12 CIJ and 10  C1J c a r r i e d  ranging information f o r  o t h e r  channels and 
During Period 3,  
need not  be descr ibed here ,  Channel 8 ClJ c a r r i e d  t h e  e l e c t r o s t a t i c  ion 
c u r r e n t  t o  t h e  l a r g e  sphere.  The combined measurements of  ion cu r ren t  
arid high frequency capaci tance w i l l  permit a complete arid q u a n t i t a t i v e  test 
of e l e c t r o s t a t i c  probe theory,  such as t h a t  of Bernstein and Rabinowitz. 
Only a very prel iminary ana lys i s  of t h i s  d a t a  lias thus  f a r  been 
performed. The q u a l i t a t i v e  conclusions j u s t  presented a r e  probably r e l i a b l e ;  
however, f u r t h e r  d e t a i l e d  reduct ion and ana lys i s  must be c a r r i e d  out .  
of t h e  r e s u l t s  of  t h e  e a r l y  ana lys i s  a r e  shown i n  Figure 3 ,  i n  t h e  form o f  
Some 
t h e  resonance r e l a x a t i o n ,  the high frequency capac i tance ,  and t h e  e l e c t r o s t a t i c  
probes,  t hese  l as t  two being normalized t o  agree with t h e  resonance r e l axa t ion  
r e s u l t  a t  t h e  peak of  t h e  E-layer. 
b 
This  comparison should be taken as qua l i -  
t a t i v e  only s i n c e  the  ion  shea th  e f f e c t s  a r e  not  independent of  he ight .  The 
L r e g i o n  c r i t i ca l  frequency indica ted  by t h e  ionogram taken j u s t  before  t h e  
f l i g h t  a t  Wallops I s l and  is a l s o  shown on the  s l i d e .  . 
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CURRENT 
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FOR ELECTRON CONCENTRATION 
1 I I I 
FIG. 4 PRELIMINARY RESULTS OF MIP 14.213 


Comparison of rocket-borne probes for electron density measurements Quarterly status report no. 5, Aug. 1 - Oct. 31, 1965

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