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

• Applicant: Professor Dr. Jürgen Oberst
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 265957274

• Final Report Year: 2019

Final Report Abstract

We improved rotational and reference system parameters of the planet Mercury, using stereo image and laser altimeter data obtained by the MESSENGER spacecraft, which operated in planet orbit from March 2011 until April 2015. Methods were developed for the precise matching of the numerous available laser altimeter range measurements with large-area stereo topographic models using data correlation techniques. Observed static offsets and trends between the two data sets enabled us to model rotational parameters (including the orientation of the rotational axis in space, the average spin rate, and slight oscillations in spin rate, i.e., librations) and to correctly tie the stereo models’ topography to the planetary reference frame. Hence, we provided the first measurement of Mercury’s annual libration using data from an orbiting spacecraft. Also, the orientation of the rotational axis and the rotational rate were re-determined. Mercury’s mean rotation was found to differ significantly from the resonant rotation rate, implying that the planet is possibly undergoing very long-period librations, caused by planetary perturbations. Using the improved rotational parameters, we created a new reference frame for Mercury, which allowed us to produce geometrically precise image and topographic maps. These constitute important tools for planning of image and altimetry data acquisition of BepiColombo, currently en route to Mercury. Our rotational models pose strong constrains on Mercury’s thermal evolution, its interior structure and the characteristics of its liquid core. In particular, the new data confirm that Mercury possesses a large molten outer core.

Publications

• (2015). First MESSENGER orbital observations of Mercury’s librations. Geophysical Research Letters, 42 (19), 7881–7889
  Stark, A., Oberst, J., Preusker, F., Peale, S. J., Margot, J.-L., Phillips, R. J., . . . & Solomon, S. C.
  
• (2015). Mercury’s resonant rotation from secular orbital elements. Celestial Mechanics and Dynamical Astronomy, 123 (3), 263–277
  Stark, A., Oberst, J., & Hussmann, H.
  
• (2015). Mercury’s rotational parameters from MESSENGER image and laser altimeter data: A feasibility study. Planetary and Space Science, 117, 64–72
  Stark, A., Oberst, J., Preusker, F., Gwinner, K., Peale, S. J., Margot, J.-L., . . . & Solomon, S. C.
  
• (2016). Observations of Mercury’s rotational state from combined MESSENGER laser altimeter and imaging data. Technische Universität Berlin, Fakultät VI - Planen Bauen Umwelt
  Stark, A.
  
• (2017). Toward high-resolution global topography of Mercury from MESSENGER orbital stereo imaging: A prototype model for the H6 (Kuiper) quadrangle. Planetary and Space Science, 142, 26–37
  Preusker, F., Stark, A., Oberst, J., Matz, K.-D., Gwinner, K., Roatsch, T., & Watters, T. R.
  
• (2018). High-Resolution Topography of Mercury from Messenger Orbital Stereo Imaging - the Southern Hemisphere Quadrangles. In The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences (Vol. XLII-3, pp. 1389–1394). ISPRS-Archives. Copernicus Publications
  Preusker, F., Oberst, J., Stark, A., & Burmeister, S.
  
• (2018). Mercury stereo topographic mapping using data from the MESSENGER orbital mission. In B. Wu, K. Di, J. Oberst, & I. Karachevtseva (Eds.), Planetary remote sensing and mapping (pp. 149–162). ISPRS Book Series. CRC Press
  Preusker, F., Oberst, J., Stark, A., & Burmeister, S.
  
• (2018). The reference frames of Mercury after the MESSENGER mission. Journal of Geodesy, 92 (9), 949–961
  Stark, A., Oberst, J., Preusker, F., Burmeister, S., Steinbrügge, G., & Hussmann, H.
  
• (2018). Thermal Effects on Camera Focal Length in MESSENGER Star Calibration and Orbital Imaging. In The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences (Vol. XLII-3, pp. 103–105). ISPRS-Archives. Copernicus Publications
  Burmeister, S., Elgner, S., Preusker, F., Stark, A., & Oberst, J.