Conductivity and electron density in Titan's atmosphere as deduced from Mutual Impedance measurements by the PWA-HASI instrument on HUYGENS
Résumé
During the descent of the HUYGENS Probe through the atmosphere of Titan, January 14th, 2005, the permittivity, Waves and Altimetry (PWA), a subsystem of the HUYGENS Atmospheric Structure Instrument (HASI) detected an ionized layer around the altitude of 60 km with two different instruments, the Relaxation Probe (RP) and the Mutual Impedance Probe (MIP). For both instruments a more detailed data analysis, including unforeseen environmental effects, was necessary to reach precise quantitative estimations of the electrical conductivity. The present work is dedicated to the MIP data analysis. New laboratory tests have been performed to correct and validate the calibration data. Temperature effects have been included and two different numerical models of MIP electrodes and circuits in the HUYGENS body environment have been used. The effect of motion of HUYGENS in the ionized atmosphere that was neglected in the first analysis is revealed and analytical estimations of this effect allow to derive more accurate values of the conductivity. The final results are discussed, compared to the RP results and electron density profiles are deduced showing more precisely the lower ionized layer.