CONSERT’s first constrains on the fine scale heterogeneity inside the nucleus of 67P/Churyumov-Gerasimenko

Abstract : Since the arrival of the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko in August 2014, a series of instruments have been observing the surface of the nucleus at distances ranging from more than 10 000 km down to less than one meter. The cameras onboard the Rosetta's main spacecraft (NAVCAM [1], OSIRIS [2]) and Philae lander (CIVA [3], ROLIS [4]) have revealed details of amazing structures giving some very partial hints about the internal structure of the nucleus. This is the case for the a few hundreds-of-meters deep pits [5] linked to the comet's activity; and the layers and terraces [6, 7, 8] revealed by the OSIRIS images. The CONSERT (Comet Nucleus Sounding Experiment by Radiowave Transmission) experiment [9] has been specifically designed to sound the interior of the nucleus and provide information on the nucleus structure at depth. The work presented here is based on the CONSERT data collected during the First Science Sequence and aims at constraining the small scale hetero-geneity inside the volumes investigated by CONSERT. The CONSERT data: The CONSERT experiment is a bistatic radar with receivers and transmitters on-board both Rosetta's main spacecraft and Philae lander. The instrument made use of electromagnetic waves at 90 MHz that propagated, during the First Science Sequence , back and forth between the transmitters and receivers onboard the lander and the orbiter through the small lobe of 67P. The data used here have been acquired with a sufficient enough signal to noise ratio (in green on Fig. 1) thus allowing a quantitative analysis of the measurements performed. Two data sets are available that correspond to approximately 30 min of measurements at West of Abydos and 90 min at East, at a rate of one sounding each 2.5 sec.