V. S. Avduevsky

Preliminary results on the Venus atmosphere from the Venera 8 descent module

Abstract The Venera 8 descent module measured pressure, temperature, winds and illumination as a function of altitude in its landing on July 22, 1972, just beyond the terminator in the illuminated hemisphere of Venus. The surface temperature and pressure is 741 ± 7°K and 93 ± 1.5kgcm −2 , consistent with early Venera observations and showing either no diurnal variation or insignificant diurnal variation in temperature and pressure in the vicinity of the morning terminator. The atmosphere is adiabatic down to the surface. The horizontal wind speed is low near the surface, about 35m/sec between 20 and 40km altitude, and increasing rapidly above 48km altitude to 100–140m/sec, consistent with the 4-day retrograde rotation of the ultraviolet clouds. The illumination at the center of the day hemisphere of Venus is calculated to be about 1% of the solar flux at the top of the atmosphere, consistent with greenhouse models and high enough to permit photography of the Venus surface by future missions. The attenuation below 35km altitude is explained by Rayleigh scattering with no atmospheric aerosols; above 35km there must be substantial extinction of incident light.

Phobos-Grunt: Russian sample return mission

Abstract As an important milestone in the exploration of Mars and small bodies, a new generation space vehicle “Phobos-Grunt” is planned to be launched by the Russian Aviation and Space Agency. The project is optimized around a Phobos sample return mission and follow up missions targeted to study some main asteroid belt bodies, NEOs and short period comets. The principal constraint is use of the “Soyuz-Fregat” rather than the “Proton” launcher to accomplish these challenging goals. The vehicle design incorporates innovative SEP technology involving electrojet engines that allowed us to increase significantly the missions energetic capabilities, as well as highly autonomous on-board systems. Basic criteria underlining the “Phobos-Grunt” mission scenario, scientific objectives and rationale including Mars observations during the vehicles insertion into Mars orbit and Phobos approach maneuvers, are discussed and an opportunity for international cooperation is suggested.

Venera 8: Measurements of Temperature, Pressure and Wind Velocity on the Illuminated Side of Venus 1

Abstract Measurements of the temperature, pressure and wind speed in the atmosphere of Venus are reported. These were obtained with the interplanetary station Venera 8, which was the first entry probe to telemeter data from the solar-illuminated side of Venus. One component of the horizontal wind velocity was obtained, for the direction from the landing site to the sub-Earth paint,σ25° from the zonal direction. This component was found to decrease from σ100 m sec−1 at an altitude of 50 km to σ0 at the ground, with the direction of flow from the day side of the planet toward the night side at all altitudes.

A Tentative Model of the Venus Atmosphere Based on the Measurements of Veneras 5 and 6

Abstract Following the flight of Venera 4 in October 1967, new in-situ measurements of the temperature, pressure and density of the Venus atmosphere were made on 16 and 17 May 1969 by the Venera 5 and 6 space probes. A description of the scientific devices and an analysis of the results of the data are presented. From the results it is concluded that all measurements performed are, in general, internally consistent. The data of the Venera 4, 5 and 6 and Mariner 5 flights which overlap in altitude agree quite well. Based on these spacecraft measurements, and taking into account some ground-based data and some additional assumptions, a tentative model of the Venus atmosphere is developed from the surface up to 300 km. The extrapolated values of temperature and pressure at the mean level of the planetary surface, taking into account possible large deviations from the adiabatic model, result in a surface temperature of 770±60K and a surface pressure of 97−30+15 atm, respectively.

Soft Landing of Venera 7 on the Venus Surface and Preliminary Results of Investigations of the Venus Atmosphere

Abstract A soft landing on the planet Venus was successfully accomplished by the automatic interplanetary station Venera 7. The temperature of the Venus atmosphere was measured during the descent and at the surface after landing. The variation of temperature and pressure with altitude on Venus was determined down to the surface by combining the temperature measurements with descent velocity derived from the Doppler shift data during the descent, and by considering the data collected previously during the flights of Veneras 4, 5 and 6.

Venera 8: Measurements of Solar Illumination Through the Atmosphere of Venus 1

Abstract Measurements of the flux of downward solar radiation through the atmosphere of Venus and at the planetary surface are reported. These were obtained with the interplanetary spacecraft Venera 8 which landed on the surface of Venus on 22 July 1972 after a 55-min parachute descent through the atmosphere. A significant flux of solar radiation was found to penetrate the entire thickness of the atmosphere, with the amount at the ground ∼1.5% of that incident on the top of the atmosphere. The variation of flux with altitude indicates that the clouds have a lower boundary at an altitude of σ35 km.

Heat Transfer in the Venus Atmosphere

Abstract The successful flights of the Venera 4, 5 and 6 probes resulted in direct, in situ measurements of the chemical composition, pressure, temperature and density of the Venus lower atmosphere, and gave rise to a tentative atmospheric model for the planet. These measurements permit a more definite discussion of the mechanisms responsible for the observed characteristics of the thermal conditions on Venus. In this paper, an approximate analysis of heat transfer processes in the Venus atmosphere is made, representing the continuing development of the preliminary study described by Avduevsky et al. Radiative fluxes have been calculated, a model of the convective motions in the lower atmosphere has been evaluated, and the importance of radiative and convective energy transfer in the planets total heat balance has been estimated.

Missions to Phobos and Other Minor Bodies

A space mission to Mars’ moon Phobos with a space vehicle of new generation currently developed by the Russian Aerospace Agency is discussed. The vehicle design incorporates innovative SEP technology focused on small propulsion electric engines which significantly improve the mission energetic capability. The project is optimized around a sample return (PSR) from Phobos and also offers an opportunity for rendezvous/sample return missions from several asteroids, comets, and NEO. Scenario, rationale, and basic profile of PSR mission are presented.