Accurate temperature and pressure measurements were made on the Vega-2 lander during its entire descent. The temperature and pressure at the surface were 733 K and 89.3 bar, respectively. A strong temperature inversion was found in the upper troposphere. Several layers with differing static stability were visible in the atmospheric structure

Blamon, Z.

Devyatkin, S. I.

Dyachkov, A. V.

Ignatova, S. I.

Kerzhanovich, V. V.

Linkin, V. M.

Lipatov, A. P.

Malyk, K.

Sanotskiy, Y. V.

Stadny, V. I.

English

NASA Technical Reports Server

VNASA TECHNICAL MEMORANDUM NASA TM-88420
VERTICAL THERMAL STRUCTURE OF THE VENUS ATMOSPHERE
PROM TEMPERATURE AND.PRESSURE MEASUREMENTS
V . M . Linkin, Zh. Blamon, A . P . Lipatov,
S.I. Devyatkin, A . V . D'yachtkov, S.I.
Ignatova, V .V. Kerzhanovich, K. Malyk,
V.I. Stadny^Ya^V. Sanotskiy, P.G. Stolyarchuk,
A.V. Terterashvili, A.A. Shurupov, and
L.I'. Khlyustova
Translation of "Vertikal'naya terraicheskaya struktura atmo-
sfery Venery po dannym izmereniy temperatury i davleniya
posadochnym apparatom 'Vega-2 ' . Predvaritel'nyye rezultaty,"
Pism'ma v AZh , Vol. 12, No. 2, 1986, pp. 100-105-
f
 l N a S A - T M - 8 8 4 2 0 ) VEETIC&1 THEB.MAL STBOCTORE N86-29752 i
Of THE V E N U S ATEOSFHERE FECH TEMPEH4TOBE. AND i
PBESSURE M E A S D R E M E N I S - (Naticnal. aeronautics
and Space AdministratioD) 9 p CSCL 03B OnclaE
• " G3/91 43476
NATIONAL AERONAUTICS AND SPACE.ADMINISTRATION
WASHINGTON, D.C. 205^6 MAY 1986
https://ntrs.nasa.gov/search.jsp?R=19860020280 2020-03-20T14:33:30+00:00Z
Till* «f>4
VERTICAL..THERMAL STRUCTURE OP THE VENUS
.ATMOSPHERE FROM TEMPERATURE' AND ' :::• •
"PRESSURE'MEASUREMENTS •
7. *»&«.(•> v.M. Linkin, Zh. Blamo'n, A.P.
Lipatov, S.I. Devyatkin, A.V. D'yachkov
S.I. Igna'tova, V.V. Kerzhanovich, K.
Malvkr B.I. Stadnvk.' et al
Leo Kanner Associates, Redwood City,
California 9,^063
National Aeronautics and Space Admini-
stration, Washington, D.C. 205^6
y'°f 98 6
10.
11. Con««cf «« C<«M N«
NASw-4005'
IX
Translation
li. lc;;l Hani
Translation of "Vertikal'naya termicheskaya struktura atmp-
sfery Venery po dannym izmereniy temperatury i davleniya
posadochnym apparatom 'Vega-2'. Predvaritel'nyye rezultaty,"
Pis'ma v AZh, Vol. 12, No. 2, 1986, pp. 100-105 "
(UDC 523.4)
Accurate temperature and pressure measurements were
made on the Vega-2 lander during its entire descent: The
temperature and pressure at the surface were 733 °K and
89.3 bar, respectively. A strong temperature inversion
was found in the upper troposphere. Several layers with
differing static stability were visible in the -atmospheric
structure.
17. K,r »c,<5. (Stlcclcd t>r Auirior(i))
Unclassified
II. OltOlbw'on }fot«a*nt
Unclassified-Unlimited
20.
Unclassified
77.
VERTICAL THERMAL STRUCTURE OP THE VENUS ATMOSPHERE
FROM TEMPERATURE AND PRESSURE MEASUREMENTS
V.M. Linkin, Zh. Blamon, A.P. Lipatov,
S.I. Devyatkin, A.V. D'yachkov, S.I.
Ignatova, V.V. Kerzhanovich, K. Malyk,
V.I. Stadnyk et al
1. Characteristics of sensors and measurement cyclogram. ' /10CH
The principal thermodynamic parameters of the ambient medium
were measured on board the Vega-2 lander using two temperature
sensors Tl and T2 and three pressure sensors PI, P2, and P3.
These sensors, together with the electronics bay, comprised the
"Meteo" instrument. Platinum resistance thermometers served as
the temperature sensors. The Tl sensor was made in the form of an
open platinum wire wound bifilarly on a ceramic frame so that
there were no mechanical stresses in it. The T2 sensor was also
a platinum wire, placed—for'-protection from the corrosive ambient
medium—inside a slender ceramic housing. The different construc-
tion of the temperature sensors.was selected based on the following
requirements: the need for a small time constant of the sensors,
resistance to considerable mechanical overloading and the corrosive
action of the ambient medium, and the need for different time'.con-
stants of the sensors for measurements with high sensitivity to small /101
temperature fluctuations over a wide temperature range. The first re-
quirement was satisfied best with a sensor made of an open thin wire.
As for this sensor, there were misgivings since a thin open wire had
been' used in the temperature sensors on four "Pioner-Venera" probes
(Seiff et al, 1980) and all these sensors gave invalid measurements
in the cloud cover (presumedly owing to their electrical short-circuit-
ing by cloud layer particles). Nonetheless, an open platinum wire
with additional protection against short-circuiting between the coil
turns and at the mounting areas was ultimately chosen as the ;
* Numbers in the margin indicate pagination in the foreign text.
1
low-inertia sensor. .The time, constants of the sensors under normal
conditions and with dry air sweeping past, them at a velocity of
approximately 7 . m/s. were as follows: T-, (sensors Tl) ^ 0.1 s;
T_ (sensor T2) ^ 3. s. The measurement range was from 200 to 800 °K;
the accuracy of measurements with allowance for errors in the .elec- •
tronics was +0.5 °K.
The sensors were mounted in the lower part of the lander, in
the gap between the toroidal shock absorber assembly and the hermetic
housing. The aerodynamic tests of the lander mockup showed that in
all the allowable descent regimes, the sensors were swept with a flow
that was unperturbed as to temperature.
The pressure sensors PI and P2 were designed for measurements
during the descent sectors that were of highest interest from the
standpoint of atmospheric structure: as the lander passed through
the cloud layers, the subcloud zone, and- the middle atmosphere.
Accordingly, sensors ensuring an accuracy of measurements higher
than on preceding landers and probes were^used. In these sensors
a quartz resonator connected to the. electrical circuit of )a_seif_-^__;
^excited^ oscillator was the sensitive element. The frequency of the
quartz resonator varied as a function of the mechanical stresses
transferred to it from the ambient pressure. Sensor P3 served in
measurements during the lower descent sector. A specific require-
ment was imposed. on it — exclusion of the possibility of dehermeti-
zation and thevincursion of the high ambient pressure, within the
hermetic housing of the lander through the inlet connection pipe
and the sensor housing. A membrane type pressure sensor, specially
developed for this experiment, with a capacitive method of measuring
membrane displacements was used. The range of measurements using
the pressure sensors PI, P2, and P3 was, respectively: 0-2, 0-20, and
2-110 bar, and the absolute accuracy of the measurements was '-^ 1,
and ^500 mbar, respectively, for API, AP2, and AP3.
•~- Sensors" PI and P2 were placed in the outer separate thermally
insulated hermetic container protecting them against high temperatures
and pressures to the;level_ ^30 bar. The measured pressure was/ap-
plied against the sensors via short tubes. The hermetic container
of the PI and ,P2 sensors was installed. on^h_e_"tora±daT_shpck absorber
assembly of the lander; the inlet openings of the tubes' were in the
lower part of the torus. . During the descent, the temperature inside
the hermetic container was monitored; at the instant the container
underwent dehermetization (v3Q bar) the temperature did not exceed
320 °K at an outside temperature of ^ 600 °K.
: a
P.ffOfl
b|
so
70
60
50
to
JO
20
10
T,K
650
550
150
J50
250
1000 2000 JOOO
Pig. 1. Results of measurements of tem-
perature (points) and pressure (crosses).
Time was measured. from the instant T3-.
Solid line—lander altitude as a function
of time
Key: a. bar b. km c. seconds
The P3 sensor was in- /102
stalled inside the main
hermetic housing of the
lander and operated dur-
ing both the descent and
on the surface.
In the results of
pressure and temperature
measurements present below,
no allowance was made for
the incident flow. Prom
the results of aerodynamic
measurements, these correc-
tions are insignificant.
In the following they will
be. introduced in the final
data of pressure and temper-
ature measurements.
The temperature measure-
ments began from the instant
T3 = 35 s before the lower
hemisphere of the lander was
jettisoned and continued during the entire descent and on the surface.
The pressure was measured from the instant T3"+ 3 s. The temperature
sensors were interrogated every 0.2 s; their signals together with
7103
JOO
Pig. 2. Temperature and pressure as functions of
altitude
Key: a. km b. bar
0.2 0.1
Pig. 3- Temperature ^inversion in
upper troposphere. Density and"
pressure also shown - -
Key: a. km b. bar
reference standard voltages ar-
rived at a 12-bit analog-to-
digital converter and "further,
in the form of two six-bit words
were fed to the memory of the
"Meteo" instrument. Prom the
memory of the instrument, the
data were outputted as a serial
binary file with a periodicity
of 200 s to the radio complex
of the lander. These data con-
taind the absolute temperature
measurements taken every 0.5 s
and the relative measurements
of temperature fluctuations (their
analysis will be made later).
The. periodicity of the pres-
sure-measurements was 0.43 s.
Prom the beginning of the measurements to the 2 bar level, the "Meteo"
instrument released data from the PI and P2 sensors in the form of
a parallel 12-bit code... When the pressure.around P2 = 2.8 bar, the
"Meteo" instrument automatically switched to sending data from the
P3 and P2 sensors. The P2 sensor ceased operating at a pressure of /104
^30 bar; its calibration measurements pertained to the,range 0-20 bar.
2. Results of measurements. The temperature and pressure were
measured over the entire sector of the descent in the Venusian atmo-
sphere. The measurement results are shown in Pig. 1. The measure-
ments with both temperature sensors are .in agreement everywhere to
within approximately 2 °K. The small difference between their read-
ings is regular in trend .and is associated mainly with the differ-
ence in the sensor time constants, which is easily seen in the regions
with a change in the temperature gradient at high lander descent rates
(the measurements of the T2 sensor lagged with respect to Tl). In
the following, mainly measurements by the Tl sensor are presented.
The results as to temperature, pressure, and altitude given in this
study are preliminary, since all corrections have not yet been incor-
porated .
Prom these data, the surface temperature is 733j:l °K; pressure,
89.3+; bar. Taking PQ = 92.1 bar as the zero reference level (RQ =
= 6052 km), adopted in the Venus International Reference Temperature,
VIRA (Sieff et al, 1984), we obtain the landing point altitude of
500 m. Prom the temperature and pressure measurements, in the hydro-
static approximation, with allowance for changes in the acceleration
due to gravity.with altitude and using the equation of state for car-
bon dioxide gas, the dependence of altitude over the landing site
on time H(t) was. calculated, also shown in Pig. 1. The altitude
^63.6 km corresponds to the beginning of pressure measurements.
The plots of the temperature and pressure as functions of alti-
tude over the landing site are shown in Fig. 2. With the exception,
of the upper sector, on the average their profile is in agreement
with the data .obtained by the.. "Venera" landers and by the "Pioner-
Venera" probes. In the lower 12-km region, the temperature and
altitude measurements have not previously been made with high ac-
curacy. Several features.of the vertical thermal structure are ob-
served, here for the first time. A strong temperature inversion at
the altitudes 62-64 km was noted (Fig.. 3). Here the minimum tempera-
ture directly under the inversion layer was 254 °K (at the altitude
of 62 km); above this level, the .temperature climbs rapidly, reaching
a maximum of 269 °K at the altitude of 63.6 km. The vertical temper-
ature profile can be clearly traced through several layers with dif-
ferent static stability. The boundaries between them occur at the
altitudes: ^8, ^38, ^45, ^56,..and ^62 km. A near-adiabatic tempera-
ture change is observed from 45 to 56 km and for the first time in
the layer to 8 km; at these altitudes thermal convection is possible.
In the remaining regions, the temperature gradient is smaller than
the adiabatic gradient and the stratification is stable.
REFERENCES /I05
1. Seiff, A., D.B. Kirk, R.E. Young et al, J. Geophys. Res. 83,
7903 (1980).
2. Seiff, A., .I.T. Schofield, A.I. Kliore et. al, in: Venus Inter-
national Reference Atmosphere, edited.by A. Kliore ,.'i.;V. Moroz,
and G. Keating, COSPAR, JPL, 1984.
Institute for Space Studies Received by editor
USSR Academy of Sciences, Moscow 25 October 1985
National Center for Space Research,
Paris, Prance
L'vov Polytechnic Institute
Astronomy Service, Verrier, Prance


Vertical thermal structure of the Venus atmosphere from temperature and pressure measurements

Vertical thermal structure of the Venus atmosphere from temperature and pressure measurements

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