Pioneer Venus Probe

TGS is still used for the highest performance pyroelectric detectors, although it may soon be largely replaced by LiTaOj. The recent successful operation of radiometers in the Pioneer Venus probe [8.41,41a] and of met. satellites such as TIROS N [8.42] has demonstrated the capabilities of TGS devices. 

One important point should be emphasized here. This is the paucity of spacecraft data on the chemical composition and thermal structure of Venus lower atmosphere below —22 km altitude (von Zahn et al., 1983). About 80% of Venus atmospheric mass is below this altitude. Furthermore, altitudes of 0-12 km span the region where the atmosphere is interacting with the surface. However, with three exceptions we have no data on the chemical composition of Venus nearsurface atmosphere. First is the older measurements of CO2 and N2 from crude chemical experiments on the Venera 4-6 landers. Second, the water-vapor profile measured by the Pioneer Venus large probe neutral mass spectrometer. Third, the measurements of water-vapor and gaseous sulfur by spectrophotometer experiments on the Venera II-I4 landers. The gas chromatograph and mass spectrometer experiments on... 

Aug. 8, 1978 Pioneer Venus 2, bus probes Atm. entry Dec. 9, 1978 (bus, large probe, 3 small probes), first successful gc and ms analyses of atm... 

Another important question is which, if any, gases in Venus atmosphere are buffered by mineral assemblages on Venus surface. Interpretations of data from Pioneer Venus and the Venera and Vega probes about the chemistry of Venus lower atmosphere and surface are based upon this assumption, which has not been verified experimentally. Instead, research shows kinetic control of reactions of SO2 and water vapor with minerals at Venus surface temperatures (Fegley and Prinn, 1989 Johnson and Fegley, 2000). 

The Pioneer Venus mission (1978) explored the atmosphere of Venus. One of the payloads was a GC system equipped with two gas columns and a TCD detector. Tlie system was used to analyze samples of the atmosphere during the probe s descent to determine the composition of Venus lower atmosphere. From these measurements, deductions were made of the gaseous sources of infrared opacity, the degree of differentiation of Venus interior, the degree of similarity between the solid bodies of Earth and Venus, and the evolution of Venus atmosphere to determine the composition atmospheric composition measurements [50]. 

Hoffman, J.H., Hodges, R.R., Wright, W.W., Blevins, V.A., Duerksen, K.D., Brooks, L.D. (1980) Pioneer Venus sounder probe neutral gas mass-spectrometer. IEEE Transactions on Geoscience and Remote Sensing, 78(1), 80-84. 

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