?Measuring the electrical properties of materials can provide important constraints on the characteristics of planetary environments.Quadrupolar probes are particularly suitable for this measurement due to their flexibility and immunity to interface effects 1.Flight instruments have been built for atmospheric and surface investigations(Huygens,Rosetta Lander). Atmospheric investigations are comparatively straightforward due to the homogeneity of the medium, but the measurements of surface and shallow subsurface material properties are more difficult due to the variability of composition,stratigraphy,and topography.In general,only the bulk characteristics of surface and subsurface materials can be measured.A limited assessment of the electrical characteristics of individual layers is possible by employing multiple arrays 2.However,the dimensions of the electrode arrays always limit the spatial resolution of such measurements.The Beagle2 lander onboard the European Mars Express Mission 3.will carry a so- called‘Mole’for the acquisition of subsurface samples 4.Apart from a temperature sensor,it will not carry any other instrumentation.Future versions of this type of vehicle can provide an attractive platform for the investigation of subsurface material properties.In this paper,we present a quadrupolar probe prototype for accommodation on a Mole-type instrument platform. The measurement principle and the basic architecture of the prototype instrument are explained.Laboratory test results are presented.The accuracy and spatial resolution of the prototype measurements are discussed,and the capabilities of this type of instrument for subsurface investigations are pointed out.
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