Thermal structure measurements obtained by the two Vega balloons show the Venus atmosphere in the middle cloud layer to be near-adiabatic, on the whole; but discrete air masses are present that differ slightly from one another in potential temperature and entropy. The Vega 1 temperatures are 6.5 K warmer than measured by Vega 2 at given pressures. Measurements taken by the Vega 2 lander on descent through these levels agree with the Vega 2 balloon data

Blamont, J.

Crisp, D.

Elson, E.

Frank, G. A.

Hlyustova, L. I.

Ignatova, S. P.

Ingersoll, A. P.

Kerzhanovich, V. V.

Linkin, V. M.

Lipatov, A. N.

Malique, C.

Preston, R.

Ragent, B.

Seiff, A.

Shurupov, A. A.

Terterashvili, A. V.

Young, R.

Caltech Authors - Main

19
86
Sv
AL
..
.1
2.
..
15
L the average backscatter level. On the whole these 
variations anticorrelate with the ambient temperature. 
An absence of large density variations in the 
Venus middle cloud layer has been reported from ear-
lier probe missions2 and is consistent with intensive 
convection and zonal flow in the atmosphere, as well 
as with a long survival time for the cloud particles. 
The decreases in the amount of coud-particle 
backscatter recorded on relatively long time scales 
might have occurred as the balloon sank into a less 
dense zone of clouds, as is apparent, for example, 
from comparison against the cloud-structure observa-
tions by various probes of the Venus atmosphere. 
The authors have discussed these wind and other 
meteorological measurements further in two of the 
Science papers. 3 , 4 
1R. S. Kremnev, A. S. Selivanov, V. M. Linkin, et al., Pis'ma 
Astron.Zh. !Z,, 19(1986) [Sov.Astron.Lett.12, 7 (1986)]. 
2R. Knollenberg, L. Travis, M. Tomasko, et al., J. Geophys. Res. 
§2., 8059 (1980) [in: Pioneer Venus, Am. Geophys. Union, Washing-
ton]. 
3 R. z. Sagdeev, V. M. Linkin, V. V. Kerzhanovich, et al., Sci-
ence ill, 1411 (No. 4 7 44) (March 1986) • 
4V. M. Linkin. v. V. Kerzhanovich, A. N. Lipatov, et al., Sci-
ence ill, 1417 (1986). 
Thermal structure in the Venus middle cloud layer 
V.M. Linkin,1 A. N. Lipatov,1 A. A. Shurupov,1 S. P. lgnatova,1 G. A. Frank,1 
L. I. Khlyustova,1 A. V. Terterashvili,1 V. V. Kerzhanovich, 1 J. E. Blamont,2 C. Malique,3 
A. Seiff,4 B. Ragent,4 A. E. Young,4 L. S. Elson,5 R. A. Preston,5 A. P. lngersoll,6 and D. Crisp6 
Institute for Space Research, USSR Academy of Sciences, Moscow, 1 
Centre National d'Etudes Spatiales, Paris, 1 
Service d'Aeronomie du Centre National de la Recherche Scientifique, Verrieres-le-Buisson, Essonne, 3 
NASA Ames Research Center, Moffett Field, California, 4 
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 5 
and Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena6 
(Submitted October 25, 1985) 
Pis'ma Astron. Zh. 12, 36-40 (January 1986) 
Thermal structure measurements obtained by the two Vega balloons show the Venus atmosphere in the 
middle cloud layer to be near-adiabatic, on the whole; but discrete air masses are present that differ slightly 
from one another in potential temperature and entropy. The Vega I temperatures are 6.5 K warmer than 
measured by Vega 2 at given pressures. Measurements taken by the Vega 2 lander on descent through these 
levels agree with the Vega 2 balloon data. 
The two Vega balloons did not float calmly at 
their equilibrium height in the Venus atmosphere1 but 
from time to time moved vertically by a few kilometers 
because of the sizable vertical flows that they en-
countered. The concomitant temperature and pres-
sure variations contain some interesting information 
on the atmospheric structure between the 54- and 
50-km levels, a region that dominates the middle cloud 
layer. 2 • 3 As pointed out on an earlier occasion 4 the 
thermal stratification is slightly unstable there, and 
convection presumably is taking place. 
When plotted in the (P, T) plane the temperature 
and pressure measurement by each Vega balloon fall 
along a straight line; the departures in T amount to 
only about ± 0.5°K. Although some isolated points 
do deviate from the prevailing line by several de-
grees , they are generally confined to time intervals 
when an ambiguity was present in the most signi-
ficant bits of the temperature telemetry, which re-
ported readings every 10 min. Thus the (P, T) data 
obtained by each balloon separately exhibit a strong 
correlation between temperature and pressure. 
For equal pressures, however, the temperatures 
measured by the two balloon probes differ uniformly 
by about 6.5°K, the Vega 1 temperatures being high-
er. Since the balloons were deployed at points ap-
proximately symmetric relative to the equator (lati-
tudes 7°. 3 N, 6°. 6 S), the offset between the two 
(P, T) lines is rather surprising. 
Figure 1 plots the temperature and pressure 
measurements acquired in the 45°-180° interval of 
east longitude. Notice· that the differential between 
the (P, T) data sets for the two balloons shows no 
appreciable longitude dependence. The cause might 
be an inherent feature of balloon measurements - the 
tendency of a balloon to move along with some par-
ticular air mass. During their flight the two Vega 
balloons evidently were located within air masses that 
had different thermal histories, with each balloon 
spending most of its time in the same air mass as it 
floated one-third of the way around Venus. 
The source of this temperature differential is of 
great interest for the atmospheric dynamics. Waves 
in the atmosphere could induce an adiabatic com-
pression, but they would account for the tempera· 
ture disparity only if their wavelength were com-
parable with the planet's circumference; otherwise 
the temperature difference should vary with longi-
tude. Another possibility is that the difference in T 
reflects transient variability in the atmosphere, or 
it might be evidence for an asymmetry between the 
northern and southern hemispheres. 
To check on the calibration of the data sensors 
we have compared the P. T measurements by the 
Vega 2 balloon against the data returned by the 
Vega 2 landing capsule as it descended through the 
middle cloud layer. As Fig. 1 indicates , the bal-
loon and lander data lie along the same straight 
15 Sov. Astron. Lett. 12( 1 ), Jan.-Feb. 1 986 0360-0327/86/01 00-15•-03 $03.00 © 1 986 American Institute of Physics 15 
© American Institute of Physics • Provided by the NASA Astrophysics Data System 
19
86
Sv
AL
..
.1
2.
..
15
L p, mbar 
650 
6Z5 
600 
575 
JOO J05 JIO J15 JZIJ 
T,°K 
FIG. 1. Pressure and temperature measurements by the Vega 1 
and Vega 2 balloons. 
line; the deviations are less than 0.5°K. More-
over each balloon carried a second temperature sen-
sor, mounted inside the nephelometer. On both Vega 
1 and Vega 2 the temperatures measured by the two 
sensors are within :::1°K of each other on the planet's 
night side, where the nephelometer was not over-
heated by solar rdiation. 
Figure 2 shows the temperature profile mea-
sured by the Vega 2 lander down to the 50-km 
level. The float heights of both balloons are specified 
as well. Heights along the Vega 2 lander curve 
have been computed from the P, T measurements by 
that vehicle. We see that below 55 km the lander 
(P, T) relation is nearly adiabatic. 
The temperatures measured by the Pioneer 
Venus Large Probe 4 lie in between the values ob-
tained by the two balloons for corresponding pres-
sures. The derivatives dT/dP determined from the 
balloon data and from the Large Probe, which de-
scended through the atmosphere at latitude 4 °. 4 N, 
have nearly equal values. In hydrostatic equilibrium, 
dT/dz = - pg·dT/dP, so the vertical temperature 
gradients also are about the same. 
Although the mean temperature lapse rate can 
be calculated from the whole data set for each bal-
loon, it is best determined for separate measure-
ment periods. To illustrate, Fig. 3a plots the (T, 
P) data for Vega 2 frame B39, taken at a time of fast 
(wd = 2.5 ± 0.5 m/sec) downflow during which the 
balloon. droped by 0.57 km. The variation in mea-
sured T with P is essentially linear. Also plotted 
here is the adiabat corresponding to an entropy S : 
26.45R (R is the gas constant). Clearly the atmo-
sphere is practically adiabatic in this instance. (The 
slight departure of the points from the adiabat in 
this frame might be a regular effect, indicating a 
mildly stable stratification of about 0.3 °K/km.) The 
adiabat shown in Fig. 3a serves as a reference line 
in the other panels of this figure . 
H, km 
60 
t5 
H0 (Vega 1)' 
Hg(Vega 2) 
Vega 2 
-------------- ~·Vega 1 
0 
250 JOO 
50 100 
t, sec 
J50 T,sec 
FIG. 2. Temperature profile indicated by the Vega 2 landing 
module, compared with the adiabat ya. The bands at H 0 repre-
sent the balloon equilibrium float heights. 
ward motion dring this frame, with a vertical velocity 
wd = 2-4 m/sec. 
One interpretation of the offset between the 
adiabats in Fig. 3b could be that when air is flowing 
downward over the balloon from above, the sensors 
might find themselves either in a new air parcel, in 
an old one entrained by the downflow, or in a mixture 
of new and old air masses. Thus the measured tem-
perature might take values in the temperature range 
covered by these air parcels . During this telemetry 
period the downflow persisted for more than 30 min, 
and the air mass could have descended from a level 
several kilometers above the balloon. 
Similar (P, T) comparisons are shown in Figs. 
3c, d for two other periods when the Vega 2 balloon 
encountered smaller vertical velocities. The balloon 
spent most of frame B3 floating at nearly constant 
height (at any rate the vertical shift was no more 
than 100 m, the pressure varying between 534 and 
T, °K 
Frame BJ9 
316 UT=26h55m5qs a 
T, °K Frame 855 
UT=Jqh5amqqS 
Jfq b 
J1Z adiabat 
JIO 
JIZ 
JOB 
590 600 610 tiZO 6JO 6QO 650 600 610 620 6JQ qQQ 650 660 570 
P, mbar 
T, OK 0 
d ~ FrameBJ c / T, K J05 UT=Dz'117mz3s _/· 310 ame 650 
Figure 3b presents analogous data for frame B55, ./ UT=J2hz7mq6' 
taken just after the terminator was crossed. Again J04 /./ JOB 
the points follow an adiabat, but it is offset from the ...-::4. 0 
reference line by 0.6°K. Actually the data from this JOJ • ......-;,~ 0 308 
frame conform to two different adiabats, spaced O. 24 °K JOZ 00 301'--......i~:....J..-_l._ _ _J_ _ _,___ 
apart. The measured points migrate from one adiabat 530 5qo 550 560 570 500 590 P, mbar 
to the other, a behavior not attributable to erroneous FIG. 3. Thermal structure of the Venus middle cloud layer ac-
decoding of the telemetry (the ambiguity in the high- cording to measurements by the Vega 2 balloon during four brief 
order bits). Most likely the measurements are evid- telemetry intervals. The lines represent different adiabats, 
ence for a new air mass participating in the down- as explained in the text. 
18 Sov. Astron. Lett.12(1 ), Jan.-Feb. 1986 Linkin et al. 18 
© American Institute of Physics • Provided by the NASA Astrophysics Data System 
19
86
Sv
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..
15
L 542 mbar); the vertical atmospheric velocity ranged 
from +0.5 to -0.8 m/sec .. Nevertheless the measured 
temperatures are distributed between a pair of adia-
bats 0.6 °K apart, migrating between them four times, 
in 20 min. For a vertical atmospheric velocity Wa::: 
0.5 m/sec, this 5-min time scale would correspond to 
a vertical scale of :::150 m for the various air parcels) . 
Throughout frame B50, except for the last few 
points (T = 308 .O °K), the data lie between two 
adiabats separated by 0. 2 °K. In this instance the 
vertical wind velocity was -0.5±0.5 m/sec. 
We conclude by summarizing the main results 
from our preliminary analysis of the Vega balloon 
data bearing on the thermal structure of the middle 
cloud layer on Venus 5 : 1) during vertical excur-
sions of each balloon, temperature correlates strong-
ly with pressure; 2) Vega 1 and Vega 2 were im-
mersed in air masses differing systematically by 
6.5 °K (at given pressure) throughout the longitude 
range 180°-70° E; 3) in the middle cloud layer the 
atmosphere is nearly: adiabatic, confirming earlier 
probe soundings; 4) the slight deviations from a uni-
form adiabat suggest the presence of discrete, small-
scale air parcels . 
1 R. z. Sagdeev, V. M. Linkin, J. E. Blamont, et al., Pis'ma 
Astron. Zh. 12, 30 (1986) [Sov. Astron. Lett. lZ,, 12 {1986)]. 
2M. Ya. Marov, E. N. Lystsev, V. N. Lebedev, N. L. Lukashevich, 
and V. P. Shari, Icarus 44, 608 {1980). 
3 B. Ragent and J. E. Blamont, J.' Geophys. Res. !!2., 8089 (1980) 
[in: Pioneer Venus, Am. Geophys. Union, Washington]. 
4A. Seiff, D. B. Kirk, R. E. Young, et al., J. Geophys. Res. !!2., 
7903 {1980). 
5v, M. Linkin, v. V. Kerzhanovich, A. N. Lipatov, et al., Science 
z;!!, 1420 No. 4744) (March 1986). 
Mean zonal winds on Venus from Doppler tracking of the Vega 
balloons 
R. A. Andreev, 1•2 V. I. Altunin, 1 V. V. Kerzhanovich, 1 L. R. Kogan,1 V. I. Kostenko, 1 
V. D. Kustodiev, 1 V. M. Linkin,1 L. I. Matveenko,1 S. V. Pogrebenko,1 V. I. Puchkov,1 
I. Ya. Tarnoruder,1 N. A. Armand,2 R. V. Bakit'ko,2 E. P. Molotov,2 A. S. Vyshlov,2 
E. L. Akim,3 J. E. Blamont,4 L. Boloh,5 G. Laurans,5 Yu. N. Gorshenkov,6 
C. E. Hildebrand,7 R. A. Preston,7 C. T. Stelzried,7 N. M. lvanov,8 V. F. Tikhonov,8 
J. Morales,9 G. Petit,9 and A. S. Selivanov10 
Institute for Space Research, USSR Academy of Sciences, Moscow. 1 
Institute of Radio Engineering and Electronics, USSR Academy of Sciences, Moscow, 2 
Department of Computer Mathematics, USSR Academy of Sciences, Moscow, 3 
Centre National d'Etudes Spatiales, Paris,' 
Centre National d'Etudes Spatiales, Toulouse, 5 
Moscow Power Engineering Institute, 6 
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 7 
Kaliningrad Flight Center, 8 
Institut Geographique National, Saint-Mandi, Val-de-Mame, 9 
and Center for the Study of Natural Resources, State Meteorology Committee, Moscow10 
(Submitted October 25, 1985) 
Pis'ma Astron. Zh. 12, 41-45 (January 1986) 
Doppler measurements of the two balloons yield provisional estimates for the mean zonal wind velocity at the 
53-54 km level in the Venus atmosphere: 69 ± 1 m/sec for Vega 1 and 66 ± 1 m/sec for Vega 2, with 
westward flow. The wind data show a perturbation which might be evidence for solar tides. 
That strong winds might exist in the upper 
cloud layer of the Venus atmosphere was first sug-
gested by ultraviolet photography from the earth.1 
Subsequent Doppler tracking of the Venera probes,2 ,3 
followed by similar measurements of the Pioneer Ve-
nus probes, 4 showed that from the 65-km level down 
to heights of about 10 km the Venus atmosphere is 
caught up in a strong zonal flow moving in the same 
sense that the planet is rotating. This phenomenon 
has not yet been adequately explained, nor has it 
been studied phenomenologically. 
Fundamentally new information on the diurnal-
longitudinal variations in wind velocity can be ac-
quired by sounding the Venus atmosphere with bal-
loons. The wind velocity can be determined from 
measurements of the trajectory of a balloon comoving 
with the wind. We will have a complete three-di-
mensional picture of how the Vega balloons moved, 
as soon as the signals recorded by the global VLBI 
network of 20 radio telescopes 5 • 6 have been suitably 
procesed. To arrive at a provisional assessment of 
the mean zonal circulation as well as the small-scale 
turbulence, we have utilized Doppler measurements 
of the balloon signal frequency, carried out and in-
terpreted in much the same way as on the Venera 4 
to Venera 8 missions . 7 
Each Vega balloon transmitted a signal whose 
frequency was generated by a thermostatically con-
trolled quartz master oscillator. The departure of 
the reception frequency f 3 from its nominal value f 0 
is the sum of two terms: the Doppler shift fo, which 
is proportional to the line-of-sight projection of the 
balloon velocity relative to the reception point, and 
the running deviation b.f 1 (t) of the oscillator fre-
quency f1•om the nominal frequency. In determining 
the balloon velocity from the measured frequencies 
17 Sov. Astron. Lett. 12(1 ), Jan.-Feb. 1986 0360-0327/86/01 00'17-03$03.00 © 1986 American Institute of Physics 17 
© American Institute of Physics • Provided by the NASA Astrophysics Data System 


English

Thermal structure in the Venus middle cloud layer

1
9
8
6
S
v
A
L
.
.
.
1
2
.
.
.
1
5
L the average backscatter level. On the whole these 
variations anticorrelate with the ambient temperature. 
An absence of large density variations in the 
Venus middle cloud layer has been reported from ear-
lier probe missions2 and is consistent with intensive 
convection and zonal flow in the atmosphere, as well 
as with a long survival time for the cloud particles. 
The decreases in the amount of coud-particle 
backscatter recorded on relatively long time scales 
might have occurred as the balloon sank into a less 
dense zone of clouds, as is apparent, for example, 
from comparison against the cloud-structure observa-
tions by various probes of the Venus atmosphere. 
The authors have discussed these wind and other 
meteorological measurements further in two of the 
Science papers. 3 , 4 
1R. S. Kremnev, A. S. Selivanov, V. M. Linkin, et al., Pis'ma 
Astron.Zh. !Z,, 19(1986) [Sov.Astron.Lett.12, 7 (1986)]. 
2R. Knollenberg, L. Travis, M. Tomasko, et al., J. Geophys. Res. 
§2., 8059 (1980) [in: Pioneer Venus, Am. Geophys. Union, Washing-
ton]. 
3 R. z. Sagdeev, V. M. Linkin, V. V. Kerzhanovich, et al., Sci-
ence ill, 1411 (No. 4 7 44) (March 1986) • 
4V. M. Linkin. v. V. Kerzhanovich, A. N. Lipatov, et al., Sci-
ence ill, 1417 (1986). 
Thermal structure in the Venus middle cloud layer 
V.M. Linkin,1 A. N. Lipatov,1 A. A. Shurupov,1 S. P. lgnatova,1 G. A. Frank,1 
L. I. Khlyustova,1 A. V. Terterashvili,1 V. V. Kerzhanovich, 1 J. E. Blamont,2 C. Malique,3 
A. Seiff,4 B. Ragent,4 A. E. Young,4 L. S. Elson,5 R. A. Preston,5 A. P. lngersoll,6 and D. Crisp6 
Institute for Space Research, USSR Academy of Sciences, Moscow, 1 
Centre National d'Etudes Spatiales, Paris, 1 
Service d'Aeronomie du Centre National de la Recherche Scientifique, Verrieres-le-Buisson, Essonne, 3 
NASA Ames Research Center, Moffett Field, California, 4 
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 5 
and Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena6 
(Submitted October 25, 1985) 
Pis'ma Astron. Zh. 12, 36-40 (January 1986) 
Thermal structure measurements obtained by the two Vega balloons show the Venus atmosphere in the 
middle cloud layer to be near-adiabatic, on the whole; but discrete air masses are present that differ slightly 
from one another in potential temperature and entropy. The Vega I temperatures are 6.5 K warmer than 
measured by Vega 2 at given pressures. Measurements taken by the Vega 2 lander on descent through these 
levels agree with the Vega 2 balloon data. 
The two Vega balloons did not float calmly at 
their equilibrium height in the Venus atmosphere1 but 
from time to time moved vertically by a few kilometers 
because of the sizable vertical flows that they en-
countered. The concomitant temperature and pres-
sure variations contain some interesting information 
on the atmospheric structure between the 54- and 
50-km levels, a region that dominates the middle cloud 
layer. 2 • 3 As pointed out on an earlier occasion 4 the 
thermal stratification is slightly unstable there, and 
convection presumably is taking place. 
When plotted in the (P, T) plane the temperature 
and pressure measurement by each Vega balloon fall 
along a straight line; the departures in T amount to 
only about ± 0.5°K. Although some isolated points 
do deviate from the prevailing line by several de-
grees , they are generally confined to time intervals 
when an ambiguity was present in the most signi-
ficant bits of the temperature telemetry, which re-
ported readings every 10 min. Thus the (P, T) data 
obtained by each balloon separately exhibit a strong 
correlation between temperature and pressure. 
For equal pressures, however, the temperatures 
measured by the two balloon probes differ uniformly 
by about 6.5°K, the Vega 1 temperatures being high-
er. Since the balloons were deployed at points ap-
proximately symmetric relative to the equator (lati-
tudes 7°. 3 N, 6°. 6 S), the offset between the two 
(P, T) lines is rather surprising. 
Figure 1 plots the temperature and pressure 
measurements acquired in the 45°-180° interval of 
east longitude. Notice· that the differential between 
the (P, T) data sets for the two balloons shows no 
appreciable longitude dependence. The cause might 
be an inherent feature of balloon measurements - the 
tendency of a balloon to move along with some par-
ticular air mass. During their flight the two Vega 
balloons evidently were located within air masses that 
had different thermal histories, with each balloon 
spending most of its time in the same air mass as it 
floated one-third of the way around Venus. 
The source of this temperature differential is of 
great interest for the atmospheric dynamics. Waves 
in the atmosphere could induce an adiabatic com-
pression, but they would account for the tempera· 
ture disparity only if their wavelength were com-
parable with the planet's circumference; otherwise 
the temperature difference should vary with longi-
tude. Another possibility is that the difference in T 
reflects transient variability in the atmosphere, or 
it might be evidence for an asymmetry between the 
northern and southern hemispheres. 
To check on the calibration of the data sensors 
we have compared the P. T measurements by the 
Vega 2 balloon against the data returned by the 
Vega 2 landing capsule as it descended through the 
middle cloud layer. As Fig. 1 indicates , the bal-
loon and lander data lie along the same straight 
15 Sov. Astron. Lett. 12( 1 ), Jan.-Feb. 1 986 0360-0327/86/01 00-15•-03 $03.00 © 1 986 American Institute of Physics 15 
© American Institute of Physics • Provided by the NASA Astrophysics Data System 
1
9
8
6
S
v
A
L
.
.
.
1
2
.
.
.
1
5
L p, mbar 
650 
6Z5 
600 
575 
JOO J05 JIO J15 JZIJ 
T,°K 
FIG. 1. Pressure and temperature measurements by the Vega 1 
and Vega 2 balloons. 
line; the deviations are less than 0.5°K. More-
over each balloon carried a second temperature sen-
sor, mounted inside the nephelometer. On both Vega 
1 and Vega 2 the temperatures measured by the two 
sensors are within :::1°K of each other on the planet's 
night side, where the nephelometer was not over-
heated by solar rdiation. 
Figure 2 shows the temperature profile mea-
sured by the Vega 2 lander down to the 50-km 
level. The float heights of both balloons are specified 
as well. Heights along the Vega 2 lander curve 
have been computed from the P, T measurements by 
that vehicle. We see that below 55 km the lander 
(P, T) relation is nearly adiabatic. 
The temperatures measured by the Pioneer 
Venus Large Probe 4 lie in between the values ob-
tained by the two balloons for corresponding pres-
sures. The derivatives dT/dP determined from the 
balloon data and from the Large Probe, which de-
scended through the atmosphere at latitude 4 °. 4 N, 
have nearly equal values. In hydrostatic equilibrium, 
dT/dz = - pg·dT/dP, so the vertical temperature 
gradients also are about the same. 
Although the mean temperature lapse rate can 
be calculated from the whole data set for each bal-
loon, it is best determined for separate measure-
ment periods. To illustrate, Fig. 3a plots the (T, 
P) data for Vega 2 frame B39, taken at a time of fast 
(wd = 2.5 ± 0.5 m/sec) downflow during which the 
balloon. droped by 0.57 km. The variation in mea-
sured T with P is essentially linear. Also plotted 
here is the adiabat corresponding to an entropy S : 
26.45R (R is the gas constant). Clearly the atmo-
sphere is practically adiabatic in this instance. (The 
slight departure of the points from the adiabat in 
this frame might be a regular effect, indicating a 
mildly stable stratification of about 0.3 °K/km.) The 
adiabat shown in Fig. 3a serves as a reference line 
in the other panels of this figure . 
H, km 
60 
t5 
H0 (Vega 1)' 
Hg(Vega 2) 
Vega 2 
-------------- ~·Vega 1 
0 
250 JOO 
50 100 
t, sec 
J50 T,sec 
FIG. 2. Temperature profile indicated by the Vega 2 landing 
module, compared with the adiabat ya. The bands at H 0 repre-
sent the balloon equilibrium float heights. 
ward motion dring this frame, with a vertical velocity 
wd = 2-4 m/sec. 
One interpretation of the offset between the 
adiabats in Fig. 3b could be that when air is flowing 
downward over the balloon from above, the sensors 
might find themselves either in a new air parcel, in 
an old one entrained by the downflow, or in a mixture 
of new and old air masses. Thus the measured tem-
perature might take values in the temperature range 
covered by these air parcels . During this telemetry 
period the downflow persisted for more than 30 min, 
and the air mass could have descended from a level 
several kilometers above the balloon. 
Similar (P, T) comparisons are shown in Figs. 
3c, d for two other periods when the Vega 2 balloon 
encountered smaller vertical velocities. The balloon 
spent most of frame B3 floating at nearly constant 
height (at any rate the vertical shift was no more 
than 100 m, the pressure varying between 534 and 
T, °K 
Frame BJ9 
316 UT=26h55m5qs a 
T, °K Frame 855 
UT=Jqh5amqqS 
Jfq b 
J1Z adiabat 
JIO 
JIZ 
JOB 
590 600 610 tiZO 6JO 6QO 650 600 610 620 6JQ qQQ 650 660 570 
P, mbar 
T, OK 0 
d ~ FrameBJ c / T, K J05 UT=Dz'117mz3s _/· 310 ame 650 
Figure 3b presents analogous data for frame B55, ./ UT=J2hz7mq6' 
taken just after the terminator was crossed. Again J04 /./ JOB 
the points follow an adiabat, but it is offset from the ...-::4. 0 
reference line by 0.6°K. Actually the data from this JOJ • ......-;,~ 0 308 
frame conform to two different adiabats, spaced O. 24 °K JOZ 00 301'--......i~:....J..-_l._ _ _J_ _ _,___ 
apart. The measured points migrate from one adiabat 530 5qo 550 560 570 500 590 P, mbar 
to the other, a behavior not attributable to erroneous FIG. 3. Thermal structure of the Venus middle cloud layer ac-
decoding of the telemetry (the ambiguity in the high- cording to measurements by the Vega 2 balloon during four brief 
order bits). Most likely the measurements are evid- telemetry intervals. The lines represent different adiabats, 
ence for a new air mass participating in the down- as explained in the text. 
18 Sov. Astron. Lett.12(1 ), Jan.-Feb. 1986 Linkin et al. 18 
© American Institute of Physics • Provided by the NASA Astrophysics Data System 
1
9
8
6
S
v
A
L
.
.
.
1
2
.
.
.
1
5
L 542 mbar); the vertical atmospheric velocity ranged 
from +0.5 to -0.8 m/sec .. Nevertheless the measured 
temperatures are distributed between a pair of adia-
bats 0.6 °K apart, migrating between them four times, 
in 20 min. For a vertical atmospheric velocity Wa::: 
0.5 m/sec, this 5-min time scale would correspond to 
a vertical scale of :::150 m for the various air parcels) . 
Throughout frame B50, except for the last few 
points (T = 308 .O °K), the data lie between two 
adiabats separated by 0. 2 °K. In this instance the 
vertical wind velocity was -0.5±0.5 m/sec. 
We conclude by summarizing the main results 
from our preliminary analysis of the Vega balloon 
data bearing on the thermal structure of the middle 
cloud layer on Venus 5 : 1) during vertical excur-
sions of each balloon, temperature correlates strong-
ly with pressure; 2) Vega 1 and Vega 2 were im-
mersed in air masses differing systematically by 
6.5 °K (at given pressure) throughout the longitude 
range 180°-70° E; 3) in the middle cloud layer the 
atmosphere is nearly: adiabatic, confirming earlier 
probe soundings; 4) the slight deviations from a uni-
form adiabat suggest the presence of discrete, small-
scale air parcels . 
1 R. z. Sagdeev, V. M. Linkin, J. E. Blamont, et al., Pis'ma 
Astron. Zh. 12, 30 (1986) [Sov. Astron. Lett. lZ,, 12 {1986)]. 
2M. Ya. Marov, E. N. Lystsev, V. N. Lebedev, N. L. Lukashevich, 
and V. P. Shari, Icarus 44, 608 {1980). 
3 B. Ragent and J. E. Blamont, J.' Geophys. Res. !!2., 8089 (1980) 
[in: Pioneer Venus, Am. Geophys. Union, Washington]. 
4A. Seiff, D. B. Kirk, R. E. Young, et al., J. Geophys. Res. !!2., 
7903 {1980). 
5v, M. Linkin, v. V. Kerzhanovich, A. N. Lipatov, et al., Science 
z;!!, 1420 No. 4744) (March 1986). 
Mean zonal winds on Venus from Doppler tracking of the Vega 
balloons 
R. A. Andreev, 1•2 V. I. Altunin, 1 V. V. Kerzhanovich, 1 L. R. Kogan,1 V. I. Kostenko, 1 
V. D. Kustodiev, 1 V. M. Linkin,1 L. I. Matveenko,1 S. V. Pogrebenko,1 V. I. Puchkov,1 
I. Ya. Tarnoruder,1 N. A. Armand,2 R. V. Bakit'ko,2 E. P. Molotov,2 A. S. Vyshlov,2 
E. L. Akim,3 J. E. Blamont,4 L. Boloh,5 G. Laurans,5 Yu. N. Gorshenkov,6 
C. E. Hildebrand,7 R. A. Preston,7 C. T. Stelzried,7 N. M. lvanov,8 V. F. Tikhonov,8 
J. Morales,9 G. Petit,9 and A. S. Selivanov10 
Institute for Space Research, USSR Academy of Sciences, Moscow. 1 
Institute of Radio Engineering and Electronics, USSR Academy of Sciences, Moscow, 2 
Department of Computer Mathematics, USSR Academy of Sciences, Moscow, 3 
Centre National d'Etudes Spatiales, Paris,' 
Centre National d'Etudes Spatiales, Toulouse, 5 
Moscow Power Engineering Institute, 6 
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 7 
Kaliningrad Flight Center, 8 
Institut Geographique National, Saint-Mandi, Val-de-Mame, 9 
and Center for the Study of Natural Resources, State Meteorology Committee, Moscow10 
(Submitted October 25, 1985) 
Pis'ma Astron. Zh. 12, 41-45 (January 1986) 
Doppler measurements of the two balloons yield provisional estimates for the mean zonal wind velocity at the 
53-54 km level in the Venus atmosphere: 69 ± 1 m/sec for Vega 1 and 66 ± 1 m/sec for Vega 2, with 
westward flow. The wind data show a perturbation which might be evidence for solar tides. 
That strong winds might exist in the upper 
cloud layer of the Venus atmosphere was first sug-
gested by ultraviolet photography from the earth.1 
Subsequent Doppler tracking of the Venera probes,2 ,3 
followed by similar measurements of the Pioneer Ve-
nus probes, 4 showed that from the 65-km level down 
to heights of about 10 km the Venus atmosphere is 
caught up in a strong zonal flow moving in the same 
sense that the planet is rotating. This phenomenon 
has not yet been adequately explained, nor has it 
been studied phenomenologically. 
Fundamentally new information on the diurnal-
longitudinal variations in wind velocity can be ac-
quired by sounding the Venus atmosphere with bal-
loons. The wind velocity can be determined from 
measurements of the trajectory of a balloon comoving 
with the wind. We will have a complete three-di-
mensional picture of how the Vega balloons moved, 
as soon as the signals recorded by the global VLBI 
network of 20 radio telescopes 5 • 6 have been suitably 
procesed. To arrive at a provisional assessment of 
the mean zonal circulation as well as the small-scale 
turbulence, we have utilized Doppler measurements 
of the balloon signal frequency, carried out and in-
terpreted in much the same way as on the Venera 4 
to Venera 8 missions . 7 
Each Vega balloon transmitted a signal whose 
frequency was generated by a thermostatically con-
trolled quartz master oscillator. The departure of 
the reception frequency f 3 from its nominal value f 0 
is the sum of two terms: the Doppler shift fo, which 
is proportional to the line-of-sight projection of the 
balloon velocity relative to the reception point, and 
the running deviation b.f 1 (t) of the oscillator fre-
quency f1•om the nominal frequency. In determining 
the balloon velocity from the measured frequencies 
17 Sov. Astron. Lett. 12(1 ), Jan.-Feb. 1986 0360-0327/86/01 00'17-03$03.00 © 1986 American Institute of Physics 17 
© American Institute of Physics • Provided by the NASA Astrophysics Data System 


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Thermal structure in the Venus middle cloud layer

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