Interpretation of Mariner 5 and Venera 4 Data on the Upper Atmosphere of Venus

Abstract Calculations have been completed on the structure of the ionosphere of Venus. Comparisons between these calculations and the results of the Mariner 5 and Venera 4 flights yield the following information on the structure of the Venus upper atmosphere: the ionosphere of Venus is of the F1 type; no more than 2% of the CO2 in the Venus ionosphere is dissociated; the relative abundance of N2 is ≤10%, in rough agreement with the Venus 4 limit of 7%; the exospheric temperature is 700±100K, the uncertainty in this result reflecting uncertainties in the CO2 vibrational deactivation coefficient and beating efficiency.