Results of the preliminary processing of the Vega 1 and 2 descender data on the cloud layer structure of the Venusian atmosphere are discussed. A photoelectric counter for aerosol particles is described together with its optical and pneumatic circuits and operation algorithm. Vertical profiles of concentrations of particles with a diameter of 0.4 microns agree quantitatively with the Pioneer-Venus and Venera 9 and 10 data. Concentrations of these particles are: in the B layer, up to 190/cu cm; in the C layer, up to 10/cu cm; and in the D layer, up to 130/cu cm. Layers have sharp boundaries with a significant vertical heterogeneity of the aerosol concentration field inside them

Mukhin, L. M.

Nenarokov, D. F.

Zhulanov, Y. V.

English

NASA Technical Reports Server

NASA TECHNICAL MEMORANDUM TM 88424
PRELIMINARY RESULTS OF MEASUREMENTS BY -'AUTOMATED PROBES VEGA _1 AND 2 OF
PARTICLE CONCENTRATION IN CLOUDS OF VENUS AT HEIGHTS 47-63™KM
Yu.V. Zhulanov, L.M. Mukhin and D.F. Nenarokov
Translation of "Predvaritel'nyye rezul'taty izmereniya na AMS
"Vega-1" i "Vega-2" kontsentratsiy chastits v oblakakh venery na
vysotakh 47-63 km", Pis'ma v AZh, vol. 12, No. 2, 1986,
pp. 123-130.
{NASA-Tfl-88424) MELIHJHftBX EESOLTS OF N86-30618
HEASOBEMENTS BY A01OMA1ED PBGEES VEGA 1 .AND
2 OB PARTICLE CGNCENTBATIGN IK-CLOUDS OF
VENUS AT HEIGHIS- 47-63 KH (National Unclas
Aeronautics and Space Administration^ 13 p G3/91 43511
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546 MAY 1986
https://ntrs.nasa.gov/search.jsp?R=19860021146 2020-03-20T13:26:28+00:00Z
ORIGINAL ?A©E IS
OF POOR QUALITY
TM 88424
2. G«*«m/».nt Acc«t««on H«.
A. Tt.u *4 Ukcu. PRELIMINARY RESULTS OF 3
 R.p<),, o.,.
MEASUREMENTS BY AUTOMATED PROBES VEGA 1 AND 2 OIMay 1986
PARTICLE CONCENTRATION IN CLOUDS OF ' ".
VENUS AT HEIGHTS 47-63 KM
1.
Yu.V. Zhulanov, L.M. Mukhin and D.F.
Nenarokov 10. V«<t Unit N«.
V. P«ilo»«»:«»g O«con.|«i.o« Norn* on4 A^^««
Leo Kanner Associates, Redwood City,
California 94063
II. Co«u«<» •• C<««< N«.
NASw-4005
Translation
I}. }p«nio'in) Ag«n<7 Nvm* w>4 A4tf««
National^Aeronautics and Space Ad-
ministration, Washington, D.C. 20546
u. Sc;;i.r-..»tc,,Noi.. Translation of "Predvaritel' nyye rezul'taty
izmereniya na AMS "Vega-1" i "Vega-2" kontsentra-tsiy chastits
v oblakakh venery na vysotakh 47-63 km", Pis'ma v AZh, vol.
j 12, No. 2, 1986, pp. 123-130.
(UDC 523.4)
le: '-o<«
Results of the preliminary processing of the Vega 1 and
Vega 2 descenders' data on the cloud layer structure of the
Venusian atmosphere are discussed. A photoelectric counter
for aerosol particles is described together with its optical
and pneumatic circuits and operation algorithm. Vertical
profiles of concentrations of particles with a diameter of
0.4 ym agree qualitatively with the Pioneer-Venus and Venera
9 and Venera 10 data. Concentrations of these particles are:
in the B layer, up to 1.9-102 cm~3; in the C layer, up to 10
cm-3, in the D layer, up to 1.3-102 cm~3. Layers have sharp
boundaries with ' a- significant vertical heterogeneity of the
aerosol concentration field inside them.
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37.
PRELIMINARY RESULTS OF MEASUREMENTS BY AMS VEGA 1 AND VEGA 2
OF PARTICLE CONCENTRATION IN CLOUDS OF VENUS AT HEIGHTS
47-63 KM
Yu.V. Zhulanov, L.M. Mukhin and D.F. -Nenarokov
Institute of Space Investigations, USSR Academy of Sciences
Moscow
In order to understand processes of the formation and evolution /I23*
of the Venusian atmosphere, particular features of circulation and
climate, investigations of its aerosol component are very important.
Together with the gas component, it basically determines the optical
and thermoradiation properties of the Venusian atmosphere and pro-
cesses of the absorption and scattering of solar radiation. In this
connection, within the framework of the "Venera" program, an experi-
ment was planned on the landers to study the vertical concentration
profile and the spectrum of particle dimensions in the cloud layer
of Venus.
Method of the Investigation
As the method of investigation, a photoelectric method of ana-
lyzing aerosols was selected; this method provides for the conversion
of a parameter being measured (particle dimension) into an electrical
signal which is convenient for further processing and transmission to
earth. In order to ensure a constant and known discharge of atmos-
pheric air during landing, the forced pumping of gas to be analyzed
by a rotor pump was used. The broad range of working pressures and
the variable landing velocity prevented the use of the pneumatic /1.24
scheme which is traditional for photoelectric counters, in which a
flow of gas to be analyzed, which with a known and constant
* Numbers in the margin indicate pagination in the foreign text.
velocity intersects the illuminated sensitive volume in the "housing"
of the pure filtered air, forms in the intake capillary; this ensures
the stability and limited space of the flow of aerosol from the cap-
illary (Belyayev et al., 1981).
An optical scheme proposed by Deryagin et al. (1962) was used in
this work. An important feature of this scheme (for conditions of a
lander) is the possibility of separating for analysis a stream of the
necessary diameter from the total gas flow by an optical method,
rather than forming it with the help of a capillary.
In conducting the experiment in the Venusian atmosphere it was
essential to consider that the counting characteristic (the depend--
ence of the measured concentration on the true value) of the counters
is ambiguous (Oeseburg et:.al., -1979), i.e. that two- values for the
true concentration of the particles (one in the working section of
the counting characteristic, before the discontinuity and the second
after the discontinuity, when the device operates in the overflow
regime) correspond in principle to the concentration value measured
by the device. In this connection, the parameters of the optical
scheme were selected in such a way as to extend'-,the working section
of the counting characteristic into the range of high concentrations
(up to 103 cm"3). On the other hand, in individual sections of the
landing trajectory, the parameters of the air dispersed system were
determined; on the basis of these it is possible to do an independ-
ent calculation of the concentrations ..of particles using a method
described in the work of Zhulanov et al. (1984).
The Construction and Basic Nodes of the Counter
The photoelectric aerosol detector LSA which was installed in the
lander of AMS "Vega-1" and "Vega-2" consists of two basic blocks: a
block of an optical detector with a pumping system and an analysis
block. The optical detector ensures- recording of individual aerosol
particles as they intersect the sensitive volume and the
H)nepumcni> a
juagtpaiHt
Fig. 1. The optical line diagram of the LSA
detector
Key: a-Power meter
b-Light guide
c-Working chamber
d-Light source
e-Objective
f-Field diagram
g-Focussing mirror
h-Receiving objective
i-Receiving diaphragm
j-Modulator
k-FEU-69 photoreceiver
1-Analysis block
transformation of impulses of light scattered by the particle (light
carries information about its size) into an electrical signal (vol-
tage impulse). The analysis block ensures processing of incoming im-
pulses by the assigned program and the transmission of results to
earth.
a) The optical diagram of the aerosol detector consists of an
optical diagram of an illuminator and an optical diagram of a
receiver. The optical line diagram of the detector is shown in fig.
1. As the light source an incandescent halogen lamp was used. The
image of the filament was projected by the objective onto a. field
diaphragm with a rectangular slit of 1.2x0.2 mm. The image of the
illuminated slit is projected by the focussing mirror into the
working chamber. The illuminating light beam coming from the chamber
falls on the light guide which, bifurcating, divides it into two
parts. One part falls on the radiation power meter, from which,
during the entire working time of the detector, information is
received. The other part of the radiation falls on the mechanical
modulator which in the assigned period of time forms a parcel of
(10-15) light impulses which go to the photoreceiver. The amplitude
of these impulses is also transmitted to earth by telemetry.
Information from the power meter makes it possible to determine
deviations in the intensity of illumination of the sensitive volume
from the nominal value and from the amplitude of the calibrated im-
pulses to determine changes in the sensitivity of the recording
photoreceiver. On the whole, both control parameters make it pos-
sible to fix the deviation of the sensitivity of the detector from
that established during ground based calibrations of it by mono-
dispersed latex"aerosols.
The optical diagram of. the receiver consists of a receiving ob-
jective which collects light scattered by the particles in a solid
55° angle and focusses this light.on the receiving diaphragm behind
which is the photoreceiver. The pattern of the intersection of the
light beam and the aerosol flow in the working chamber is projected
by the objective onto the receiving diaphragm. In this case the
photoreceiver "sees" only part of the intersection pattern - the
sensitive volume - through the diaphragm. The diameter of the dia-
phragm and the thickness of the illuminating light beam in the work-
ing chamber determine the size of the sensitive volume. Thus, in the
optical diagram used, a small zone - the sensitive volume - is sep-
arated in the total flow of gas to be analyzed by an optical method.
According to Knollenberg and Hunten's (1979) data, the number of
particles of diameter >_0.6 ym in the cloud layer of the Venusian at-
mosphere reaches ~5«lo2 cm~3. Taking account of these data, the size
of the sensitive volume (5-10"^ cm3) was selected such that it was
possible to record concentrations up to 10^ cm~3 with an error of cor-
respondence of not more than 5%. According to data of Rossow et al. /126
(1980), the cloud layer of Venus is heterogeneous and it is not known
whether Knollenberg and Hunten's (1979) data refer to the region of
minimum or maximum concentrations and for this reason the maximum
concentration measurable by the LSA is taken with an .allowance.
Calibration of the aerosol detector, i.e. establishment of the
dependence of the amplitude of the impulse on particle size, was
done by a set of monodispersed latex aerosols. The sensitivity of
the detector itself was 0.3 ym and the broadening of the spectrum
of dimensions at the half altitude was -15%. At the established
nominal sensitivity, the current from the power meter and the ampli-
tude of the calibrated impulses from the photoreceiver were fixed.
b) The structural diagram of the analysis block is shown in
fig. 2. When the particle5:intersects the sensitive volume, the im-
pulse of the light scattered by it is recorded by the FEU-69 photo-
receiver, .from the output of which comes a current signal which is
proportional to the intensity of the scattered light. The "current-
voltage" transformer transformed the current impulses into voltage
impulses, the amplitude of which was proportional to the dimensions
of the particles. These impulses were recorded on four measurement
channels.
1. The first channel records impulses, the amplitude of which
exceeds the amplitude of impulses from particles of diameter >_0.35
ym, from the amplifier for the photocell.
2. The second channel, the input comparator of which is adjusted
to a higher threshold voltage than in the first channel, makes it
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possible- to obtain a ver-
tical profile of the con-
centrations of particles of
diameter ^ ,0.4 ym with the
same spatial resolution as
in the case in which during
the operation of the device
on the lander the adjust-
ments turn out to be above
the response threshold of
the comparator of the first
channel and it will be
blocked.
/127
Fig. 2. Structural diagram of the ana-
lysis block of the LSA
Key: a-Channel
b-Comparator
c-Counter
d-Output of a number of particles
in 0.43 s
e-Amplifier for photocell
f-"Current-voltage" transformer
g-Ten-channel analyzer
h-Output of the entire spectrum
in 200 s
i-Amplitude-time analyzer
j-Memory
k-Output of parameters in 200 s
1-Telemetry
3. The third channel
performs an amplitude ana-
lysis of the impulses com-
ing in from the detector
and it is a 10-channel dif-
ferential analyzer. It
makes it possible to obtain
a spectrum of the dimen-
sions of the particles in
the sample to be analyzed.
The number of particles in
each of the 10 channels is
by turns, with an interval
of 4.3 s, put out in digital form to the telemetry. The sensitivity
threshold of this channel was established to be still higher, it re-
cords particles of diameter >0.5 ym. This was also done from con-
siderations of duplication, in the case of blockage of both the
first and second channels during strong adjustments on board the
lander.
4. The fourth channel measures the amplitudes of the impulses
coining from the particles (with the help of a 256-channel amplitude
analyzer), their duration and the time until the next impulse. The /128
temporal diagram of the operation of this channel ensures that we
will obtain five spectra of the dimensions of particles which are
evenly arranged along the working section of the landing trajectory
(with an interval of -100 s). In this channel, calibrated impulses
from the mechanical modulator, which responded at the beginning of
the recording of each spectrum, were also recorded. The separation
of the calibrated impulses from the mass of impulses from the par-
ticles is done on the basis of their short duration (in comparison
with the duration of impulses from the particles) and the regularity
with which they come.
E xp e r ime n ta1 Results
During the experiment conducted on 11 and 15 June 1985, both
aerosol counters on the AMS "Vega-1" and,"Vega-2" landers were
switched on at altitude ~63 km and finished their work in the work-
ing section of the landing trajectory (to altitude ~47 km) in accord-
ance with the assigned program. An analysis of the control para-
meters revealed a drop in the sensitivity of the counters (-15%) in
comparison with that established during the ground calibration be-
cause the supply in the light source was lower than the nominal
value. Preliminary calculations showed that evidently, because of
this, the first channel recorded particles of diameter ^0. 4 ym.
The averaged vertical profiles of the concentrations of par-'
tides of diameter >_0.4 ym which were calculated from the data ob-
tained on the concentrations of particles (with interval 0.43 s) for
both experiments with temporal resolution 4.3 s are presented in
fig. 3. As is clear from the figure, in these experiments, which
were conducted on the night side of the planet at an interval of 4
days, identical concentration profiles were obtained (these coincide
in their basic features with the profiles obtained by ISAV-A de- '-
vices). This confirms the existence of a stable structure of the
0 -
62 SO 58 56 54 JO A.KM
Fig. 3. Vertical profiles of
the' concentrations of particles
of diameter >0.4 pm in the
cloud layer K=47-63 km accord-
ing to experimental data:
l-"Vega-l", 2-"Vega-2", 3-
"Pioneer-Venera" (Knollenberg
and Hunten, 1980).
Key: a-N, cm-3
b-h, km
cloud layer of the Venusian atmos-
phere. In the second experiment
the concentration of particles in
the upper cloud layer turned out
to be perceptibly lower than in
the first; this indicates its hor-
izontal heterogeneity which was
noted in works of Rossow et al.
(1980) and Moroz et al. (1982).
We must note also the significant
vertical variability of the con-
centrations of aerosols inside
the cloud layers.
According to the results of
previous experiments - nephelo-
metric experiments (Marov et al.,
1978;/Ragent and Blamont, 1980)
and the spectrometry of dimen-
sions (Knollenberg and Hunten,
1980), several stable cloud layers
are isolated in the cloud layer in
the range of altitudes from 47-63
km:
upper cloud layer, . --ysabbve'. 57 /km
layer D
intermediate layer C 50-57 km
lower cloud layer, 47-50 km
layer B
A comparison of the profiles of particle concentrations in the
cloud layer of the Venusian atmosphere obtained in the "Vega" experi-
ment with the profile obtained in the basic "Pioneer-Venera" probe
shows their good qualitative agreement. The following quantitative
differences exist:
a) The levels of particle concentrations in the upper (up to
1.4'102 cirr3) and lower (up to 1.9-102 cm~3) cloud layers are lower
than those obtained in the "Pioneer-Venera" experiment. The concen-
trations of particles (~10. cm~3) in intermediate layer C also turned
out to be substantially (by approximately one order of magnitude)
lower. The discrepancies found may result from the spatial and tem-
poral heterogeneities of the concentration field of aerosols in the
Venusian atmosphere.
b) A downward shift was observed in the boundaries of the sep-
arate cloud layers. The agreement of the boundaries of the cloud
layers in the two experiments at 4 day intervals on the night side
and their upward shift on the day side may indicate that these boun-
daries are related to definite temperature levels (isotherms). On
the day side the isotherms rise and the rise in the boundaries of
the cloud layers in "Pioneer-Venera" is related to this; on the
night side the isotherms drop and this is accompanied by a drop in
the boundaries of the cloud layers. The relation between the boun-
daries of the cloud layers and the isotherms and the clarity of these
boundaries allow us to propose that they result from phase conver-
sions of the components of the Venusian atmosphere which are accom-
panied by the formation of a dispersed phase. This is confirmed by
the fact that the sharpness of the boundaries of the cloud layers is
maintained under conditions of well-developed vertical turbulence.
Preliminary Conclusions
1. The structure of the cloud layer of the Venusian atmosphere
in the range of altitudes of 47-63 km which was obtained by a photo-
electric method in the "Vega" experiment basically agrees with the
results of the "Venera-9", "Venera-10", "Pioneer-Venera" and "Vega"
(ISAV-A) device experiments. The vertical particle concentration
profiles which were obtained indicate pronounced boundaries between
layers B, C and D.
2. The levels of concentrations of particles of diameter >0.4 ym
which were measured on the night side in all layers (especially in
layer C) are substantially lower than in the similar experiment done
on "Pioneer-Venera" on the day side of the planet.
3. Cloud layers are evidently formed during phase conversions
of components of the Venusian atmosphere and their position is deter-
mined by the. altitude of the isotherms which correspond to these
phase conversions.
10
Belyayev, S.P., Nikoforova, N.K., Smirnov, V.V. and Shchelchkov, G.
(illeg.), Optiko-elektronnyye metody izucheniya aero20ley [Op-
tical- e lee trorTIF~metKoHT^±sTu5yIng^erosoT^Energoizdat,
Moscow, (illeg.), p. 25.
Deryagin, B.V., Vlasenko, G.Zh. and Storozhilova, A.I. J. (illeg.)
Sci. l]_, 605 (1962) .
Knollenberg, R.G. and Hunten, D.M., Science 203, 792 (1979).
Knollenberg, R.G. and Hunten, D.M., J. Geophys. Res. 85, 8039 (1980).
Marov, M.Ya., Lystsev, V.Ye. and Lebedev, V.N., Preprint IPM AN
SSSR, 144 (1978). ""
Moroz, V.I., Moshkin, B.Ye., Ekonomov, A.P., Golovin, Yu.M., Gnedykh,
V.I. and Grigor'yev, A.V. Pis'ma Astron. zhurn. 8_, 409 (1982).
Oeseburg, F., Mooij, Ch.H., Roos, R., J. Aerosol. Sci 10, 591 (1979).
Ragent, B.,and Blamont, J., J. Geophys. Res. 85, 8089M1980).
Rossow, W.B., Del Genio, A.D., Limaye, A.D. and Travis, L.D., J.
Geoph. Res. 85, 8107 (1980).
Zhulanov, Yu.V., Lushnikov, A.A. and Nevskiy, I.A., J. Aerosol.
Sci. 15, 69 (1984).
11


Preliminary results of measurements by automated probes Vega 1 and 2 or particle concentration in clouds of Venus at heights 47-63 KM

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