Rotational Parameters and Reference System of Mercury from MESSENGER Laser Altimetry and Stereo Topographic Models

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We propose to determine or improve rotational and reference system parameters of the planet Mercury, using stereo image and laser altimeter data obtained by the MESSENGER spacecraft, currently in orbit about this innermost Solar System planet. The rotational parameters (including the orientation of the rotational axis in space, the average spin rate, and slight oscillations in spin rate, i.e., librations) will be determined from precisely matching the large numbers of available laser altimeter profiles with large-area static stereo topographic models using data correlation techniques. Static offsets and trends between the two data sets will also be determined and enable us to correctly tie the stereo models topography to the planetary reference frame. Using the improved rotational model, a geometrically precise image map of the planet will be derived, which will be an important tool for planning future missions to Mercury. Rotational models bare on Mercurys interior structure and the characteristics of its liquid core. On the basis of the new derived rotational model, the interior of the planet and its thermal evolution will be critically discussed.