PWA-HASI Measurements of Titan Surface Permittivity at Huygens Landing Point

After HUYGENS landing on Titan, ground permittivity measurements were performed by the mutual impedance (MI) technique during approximately 30mn. The MI probe designed mainly for atmospheric conductivity was set in a dedicated surface mode, working at 5 different frequencies between 45 and 5760 Hz. The measured impedance was processed in the Permittivity, Waves, and Altimetry (PWA) analyzer, a subunit of the Huygens Atmospheric Structure Instrument (HASI). The array configuration on the booms, together with the coupling between the soil and the atmosphere, required a careful evaluation of the attitude of the Huygens Probe on the surface for assessing the dielectric properties with good accuracy. As for atmospheric measurements a detailed numerical model of the HUYGENS conductive body on a flat surface was used for derivation of the ground permittivity. The ground was assumed homogeneous. The accuracy of the results as a function of the landing geometry is estimated and comparisons are made with laboratory samples measurements and CASSINI radar large scale measurements.