Simulation of radar and radiometer signals remote sensing cometary surface and subsurface structures

Results of numerical calculations in the microwave range are presented concerned with the reflection, backscattering, and emission coefficient of simulated cometary surfaces as a function of signal frequency, angle of incidence, polarization, and surface roughness. The variations of the dielectric permittivity and loss tangent are estimated as to be expected for typical cometary surface conditions. The spatial resolution of potential Rosetta radar measurements is discussed. The subsurface penetration depth is given and a one-layer model is introduced. Preliminary results from experimental investigations are also presented simulating radar measurements probing a cometary surface in the frequency range 8 to 12.5 GHz. A special calibration technique using time domain transformation is applied to resolve the cometary reflection coefficient against background noise as to be expected in a simulation chamber. The results are discussed for different surface conditions and it is shown how specific surface and subsurface parameters can be determined