CONSERT

The CONSERT radar was to perform tomography of the nucleus by measuring electromagnetic wave propagation from the Philae lander and the Rosetta orbiter throughout the comet nucleus in order to determine its internal structures and to deduce information on its composition. The related lander and orbiter electronics were provided by France and both antennas were constructed in Germany. The experiment was designed and built in France by Laboratoire de Planétologie de Grenoble (LPG now IPAG) and by Service d'Aéronomie in Paris (SA now LATMOS), in Germany by the Max Planck Institute for Solar System Research (MPS) in Göttingen. The Principal Investigator of CONSERT is Dr. Wlodek Kofman (IPAG), Director of Research at CNRS.

On 13 November 2014, the experiment unexpectedly provided information to locate Philae after it had bounced into an unknown place.

Scientific objectives

The scientific objectives of the CONSERT experiment are the determination of the main dielectric properties and, through modelling, to set constraints on the cometary composition (materials, porosity, etc.), to detect large–size structures (several tens of meters) and stratification, to detect and characterise small–scale irregularities within the nucleus.

A detailed analysis of the radio–waves which have passed through all or parts of the nucleus will put real constraints on the materials and on inhomogeneities and will help to identify blocks, gaps or voids. From this information, scientists will attempt to answer some fundamental questions of cometary physics. How is the nucleus built up? Is it homogeneous, layered or composed of accreted blocks (cometesimals, boulders)? What is the nature of the refractory component? Is it chondritic as generally expected or does it contain inclusions of unexpected electromagnetic properties?

In more detail, the purpose of CONSERT experiment is to measure the following quantities:

• The mean permittivity of the comet nucleus is derived from the group delay of the main path introduced when the comet is inserted into the propagation path. The permittivity enables to identify the electrical properties of the material found in the comet nucleus.
• The mean absorption of the comet nucleus is derived from the radiowave path loss as the signal propagates through the comet nucleus. The absorption identifies the class of materials found in the comet nucleus.
• The structure of the received signal, the number of different paths and their variation with the propagation path are related to the size of the cometesimals and to the reflection coefficient at internal interfaces.
• The correlation length of the measured signal as a function of the orbit position is related to the size of the irregularities or small structures inside the comet.
• The volume scattering coefficient is derived from the nature of the observed signal. The volume scattering coefficient measures the homogeneity of the interior of the comet nucleus.