Pioneer Venus Orbiter radio occultations of the Venus atmosphere in direct comparison with Venus Express VeRa and Akatsuki radio occultations

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The radio science experiment VeRa on Venus Express sounded the atmosphere and ionosphere of Venus from 2007 to 2014 by radio waves and provided the largest Venusian radio occultation set of 900 temperature, pressure, neutral number density and electron density profiles, respectively, to date. Another large data set was provided by the Pioneer Venus Orbiter (PVO) radio occultation experiment (PVO ORO) from 1978 to 1988. The PVO ORO profiles, however, are not or not easily available in public archives, but the raw data files recorded by The NASA Deep Space Network antennas, in a binary readable data format, are.We propose to reprocess these raw PVO ORO data files with modern software routines, actually used for Venus Express and Mars Express in daily routine, in order to process, archive, and therefore preserve these PVO ORO higher science data products for the future. Important scientific objectives are the direct comparison of the PVO ORO profiles observed during one of the strongest solar cycles with those from VEX-VeRa and Akatsuki, observed during the current relatively weak solar cycle, to reveal long term changes in neutral atmosphere temperature, in absorptivity by gaseuos H2SO4, and in ionospheric electron density. First attempts have shown that the altitude uncertainty of the PVO ORO profiles can be reduced significantly by using the newly processed and much more accurate PVO orbit file which by itself would justify a reprocessing to preserve this valuable scientific data set for future generations. We are currently the only team on this planet able and experienced for this reprocessing and the full exploitation of this special data set.