Venus: Mass, Gravity Field, Atmosphere, and Ionosphere as Measured by the Mariner 10 Dual-Frequency Radio System

Abstract

Analysis of the Doppler tracking data near encounter yields a value for the ratio of the mass of the sun to that of Venus of 408,523.9 +/- 1.2, which is in good agreement with prior determinations based on data from Mariner 2 and Mariner 5. Preliminary analysis indicates that the magnitudes of the fractional differences in the principal moments of inertia of Venus are no larger than 10(-4), given that the effects of gravity-field harmonics higher than the second are negligible. Additional analysis is needed to determine the influence of the higher order harmonics on this bound. Four distinct temperature inversions exist at altitudes of 56, 58, 61, and 63 kilometers. The X-band signal was much more rapidly attenuated than the S-band signal and disappeared completely at 52-kilometer altitude. The nightside ionosphere consists of two layers having a peak density of 10(4) electrons per cubic centimeter at altitudes of 140 and 120 kilometers. The dayside ionosphere has a peak density of 3 X 10(5) electrons per cubic centimeter at an altitude of 145 kilometers. The electron number density observed at higher altitudes was ten times less than that observed by Mariner 5, and no strong evidence for a well-defined plasmapause was found.

Venus Atmospheric Thermal Structure and Radiative Balance

“…The feasibility of the radio occultation technique to obtain atmospheric profiles of temperature and density with altitude was first demonstrated by Mariner 4 at Mars (Kliore et al 1965) and then at Venus by Mariner 5 (Kliore et al 1967) using both one way (spacecraft to Earth), and two way (Earth to spacecraft to Earth) occultations (Howard et al 1974), generally at two frequencies (X and S band). Venera 9/10 occultations at 32 cm (Kolosov et al 1978;) and 15/16 at 5 and 13 cm wavelengths (Yakovlev et al 1987) orbiters also obtained radio occultation profiles by using these radio frequencies.…”

Radio occultation experiment of the Venus atmosphere and ionosphere with the Venus orbiter Akatsuki

“…Above the cloud the temperature increases monotonically with latitude, leading to the weakening of the mid-latitude jets with height (Newman et al, 1984). The static stability is near neutral in the middle and lower cloud region (50-55 km), implying vertical convection driven by upwelling thermal radiation, while it is weakly stable below this height and strongly stable above (Fjeldbo et al, 1971;Howard et al, 1974;Tellmann et al, 2009). The overall stable stratification sustains vertical propagation of gravity waves; wavy temperature structures which might be associated with gravity waves have been observed by radio occultation (Howard et al, 1974;Hinson and Jenkins, 1995).…”

Venus cloud properties: Infrared opacity and mass mixing ratio

“…Then, with R = 2 x 106 cm 2 sec -2 K -', g = 870 cm sec -2 , and y = 5 K km -1 , which is very close to the average lapse rate at the levels of interest according to the Mariner 10 radio science investigation (Howard, et al, 1974;cf. Fig.…”

“…This follows from comparing the brightness temperature at normal incidence (T, = 255 K) with the temperature profile inferred from the Mariner 10 radio science investigation (Howard, et al, 1974;see Thus, even though inhomogeneities are known to exist in the Venus cloud structure, there is evidence that they may not be so severe as to come into serious conflict with a homogeneous model. Also, certain quantities, such as the particulate mass mixing ratio, are important mainly in the mean; and the mean values should be fairly independent of the degree of homogeneity.…”

“…In addition, many other studies have contributed to the growing body of knowledge about the Venus clouds. Among these are studies based on the data provided by the various Mariner and Venera space probes, which contribute information on the temperature profile (Fjeldbo, et al, 1971;Howard, et al, 1974) and molecular composition (Vinogradov, et al, 1968) of the atmosphere, as well as information on inhomogeneities within the clouds themselves (Murray, et al, 1974); polarization studies which contribute to the determination of refractive indices and particle sizes (Coffeen and Gehrels, 1969;Hansen and Arking, 1971;Hansen and Hovenier, 1974); spectroscopic studies in the near infrared which provide cloud opacities in this region of the spectrum (Belton, 1968;Belton, et al, 1968); and intermediate infrared limb darkening studies, which provide cloud opacity data complementary to those of the present study (Westphal, 1966;Samuelson, 1968;Chase, et al, 1974).…”