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Observations of the nightside Venus ionosphere: Final encounter of the Pioneer Venus Orbiter Ion Mass Spectrometer
Author(s) -
Cloutier P. A.,
Kramer L.,
Taylor H. A.
Publication year - 1993
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/93gl02423
Subject(s) - orbiter , venus , ionosphere , atmosphere of venus , physics , altitude (triangle) , radio occultation , ion , atmospheric entry , atmospheric sciences , astrobiology , astronomy , geometry , mathematics , quantum mechanics
During the last orbital sequences of the Pioneer‐Venus spacecraft prior to final encounter and atmospheric entry, data were obtained by the Orbiter Ion Mass Spectrometer (OIMS) at the lowest periapsis altitudes of the mission. These data verified OIMS observations of the nightside ionospheric peak reported earlier in the mission, and revealed additional details related to composition, energetics and maintenance of the nightside ionosphere. OIMS observations of the ion peak during the final encounter sequence are compared with radio occultation data and OIMS peak observations obtained earlier. OIMS ion density and Orbiter Electron Temperature Probe (OETP) electron density are found to correlate near the peak. Coupling of mass channels 30 and 32 during nightside passes is observed and its interpretation considered. Changes in high altitude composition of the nightside ionosphere, especially the relative changes in O + and H + , are described.