Polar ionic conductivity profile in fair weather conditions. Terrestrial test of the Huygens/Hasi-PWA instrument aboard the Comas Sola balloon

The permittivity wave and altimetry (PWA) instrument is a part of the CASSI NI/HUYGENS HASI experiment and was designed to determine the electrical par ameters of the atmosphere of Titan in 2004. In December 1995, a balloon cam paign was conducted in Leon, Spain, to test the HASI onboard hardware and s oftware using a HUYGENS probe mock-up in an electromagnetic-disturbance-fre e environment (mainly from power emission lines at 50 Hz). This work is con cerned with the measurements of small ion polar conductivities and DC field s using the PWA relaxation probes (RP). The two RP electrodes were periodic ally set to +/-5 V relative to the conductive surface of the mock-up and al lowed to discharge in the surrounding atmosphere, The polar components of c onductivity are calculated from the discharge time, and the DC field from t he floating potential differences once the electrodes reach equilibrium. In spite of some observed effects, such as mock-up charging or oscillations i n the measurement of potential, the conductivity measurements are coherent and in good agreement with the obtained results in other experiments. The c onductivity data were collected in 'fair-weather' conditions, up to 30 km d uring a 4-h flight, every 72 s, giving an attitude resolution better than 4 00 m. We also discuss the DC field data that do not lead, in presence of ch arging effects, to a straightforward measurement of the natural DC field. T he Comas Sold balloon flight, first real test of the PWA experiment in the terrestrial atmosphere, confirmed the validity of the ionic conductivity me asurements but raised the problem of a reliable interpretation of the DC fi eld. (C) 2001 Elsevier Science Ltd. All rights reserved.