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Rotation period of Venus estimated from Venus Express VIRTIS images and Magellan altimetry |
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| Authors: | NT Mueller J Helbert S Erard G Piccioni P Drossart |
| Institution: | 1. Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany;2. Institute of Planetary Research, DLR, Rutherfordstr. 2, 12489 Berlin, Germany;3. LESIA, Observatoire de Paris, 61 Avenue Observatoire, F-75014 Paris, France;4. IASF-INAF, via del fosso del cavaliere 100, Rome I-00133, Italy;1. Cornell University, Dept of Astronomy, 318 Space Sciences Building, Ithaca, NY, 14853, USA;2. Observatoire de Paris, LESIA, 5 Place Jules Janssen, 92195 Meudon Cedex, France;3. University of Wisconsin-Madison, Space Science and Engineering Center, 1225 West Dayton Street, Madison, WI 53706, USA;4. Jet Propulsion Laboratory, M/S 183-501, 4800 Oak Grove Drive, Pasadena, CA 91109 USA |
| Abstract: | The 1.02 μm wavelength thermal emission of the nightside of Venus is strongly anti-correlated to the elevation of the surface. The VIRTIS instrument on Venus Express has mapped this emission and therefore gives evidence for the orientation of Venus between 2006 and 2008. The Magellan mission provided a global altimetry data set recorded between 1990 and 1992. Comparison of these two data sets reveals a deviation in longitude indicating that the rotation of the planet is not fully described by the orientation model recommended by the IAU. This deviation is sufficiently large to affect estimates of surface emissivity from infrared imaging. A revised period of rotation of Venus of 243.023 ± 0.002 d aligns the two data sets. This period of rotation agrees with pre-Magellan estimates but is significantly different from the commonly accepted value of 243.0185 ± 0.0001 d estimated from Magellan radar images. It is possible that this discrepancy stems from a length of day variation with the value of 243.023 ± 0.002 d representing the average of the rotation period over 16 years. |
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