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Description
Enceladus Explorer (EnEx) is a proposed DLR space probe to explore Saturn's moon Enceladus for signs of extraterrestrial life. Geyser eruptions at the south pole indicate the presence of a salt water ocean with hydrothermal vents below the moon’s ice shell, a possible home for extraterrestrial life. The envisioned EnEx probe would land at a safe distance to one of Enceladus' active geysers and then deploy a steerable melting probe, ‘IceMole’, that will burrow through the ice until it arrives as a near-surface water pocket, and there perform in-situ tests for microbial life.
To sucessfully locate the water pocket and avoid obstacles, including cavities, rocks and soil, IceMole will need to possess a radar based sounding system to map its immediate surroundings in three dimensions and to estimate its position relative to the reference points of the lander, the suraface and the target water pocket. A chief consideration is the optimal frequency range, the size of IceMole limits the wavelength at which it can transmit, transmission of very high frequencies radio waves )f > 100 MHz). Hence such a system requires accurate knowledge of the dielectric properties of the ice on Enceladus at very high frequencies, and their further dependence on temperature, density, salinity and pH level. In particular the attenuation rate is thought to increase sharply at frequencies around 1 GHz, limiting the range and bandwidth (and hence resolution) of a given radar system. A field test in the Austrian Alps will be conducted in February next year to test the feasibility of frequency modulated radar as a distance reckoning method, and obtain accurate estimates of in-ice refractive index and attenuation rate.
