A characterization of a comet nucleus interior:: inversion of simulated radio frequency data

Radio transmission through the nucleus of the comet Wirtanen, as developed in the CONSERT experiment on the ROSETTA mission, is designed to provide information on the electrical properties of the cometary interior. In order to determine what information can most readily be obtained, we first introduce an analytical model of the nucleus permittivity. We then use the WKB approximation to describe the propagation of waves through the nucleus model assuming a radio frequency of 90 MHz, the frequency chosen for the experiment. With one end of the propagation path on the surface of the comet, and the other in a vehicle orbiting the nucleus, it is shown that the signal at the orbiting end of the path must be back-propagated to the surface of the nucleus of the comet in order to obtain a correct interpretation of the data. We show how the mean permittivity along each propagation path can be obtained and how this can be used to obtain information about the large scale structure of the nucleus. Finally we discuss how the permittivity distribution found can be used to constrain the nature of the material in the interior of the nucleus. © 1999 Elsevier Science Ltd. All rights reserved.