DDA 36th Meeting, 10-14 April 2005
Session 5 Posters
Display, Monday, April 11, 2005, 5:25-7:00pm

Previous   |   Session 5   |   Next

[5.07] The Orbits of the Major Saturnian Satellites and the Gravity Field of the Saturnian System

R. A. Jacobson, P. G. Antreasian, J. J. Bordi, K. E. Criddle, R. Ionasescu, J. B. Jones, R. A. Mackenzie, M. C. Meek, F. J. Pelletier, D. C. Roth, I. M. Roundhill, J. R. Stauch (JPL/Caltech)

Prior to the Cassini Tour of the Saturnian system Jacobson(2004 {\em AJ}\, 128, 492) determined the orbits of the Saturnian satellites and a revised Saturnian system gravity field from Earth-based astrometry and observations acquired with the Pioneer~11 and Voyager spacecraft. We have been extending that work to include additional Earth-based astrometry, Cassini Doppler tracking data, radiometric range, and optical navigation imaging. Results based on data taken during the Cassini close flyby of Phoebe and on through the first Titan flyby appeared in Jacobson {\em et al.} (2004 {\em BAAS} 36(4), 1097). In this paper we report on the current status of the orbits and gravity field. The data set now contains Cassini data acquired during the January 2005 encounter with Iapetus, the subsequent February and March encounters with Enceladus, and three additional flybys of Titan. The table below gives our latest values for the gravity parameters (parameters without uncertainties were not estimated). \vspace*{-2ex} \begin{center}\begin{array}{l@{\extracolsep{-1ex}}l l@{\extracolsep{+1ex}}l} \hline\hline \noalign{\smallskip}\multicolumn{1}{l}{Parameter} &\multicolumn{1}{c}{Value} & \multicolumn{1}{l}{Parameter} & \multicolumn{1}{c}{Value} \\ \noalign{\smallskip} \hline \noalign{\smallskip} \begin{array}{l} GM\rm system \end{array} &\hspace{1.5ex} \begin{array}{l@{\,±,}l} 37940500. & 36. \end{array} & \begin{array}{l} GM\rm Phoebe GM\rm Phoebe \end{array} &\hspace{2.3ex} \begin{array}{r@{\,±,}l} 0.553 & 0.001 \end{array} \\ \begin{array}{l} GM\rm Mimas\\ GM\rm Enceladus\\ GM\rm Tethys\\ GM\rm Dione\\ \end{array} &\hspace{5ex} \begin{array}{r@{\,±,}l} 2.540 & 0.016\\ 7.205 & 0.017\\ 41.210 & 0.008\\ 73.112 & 0.004 \end{array} &.\begin{array}{l} J2 \\ J4 \\ J6 \\ J8 \\ \end{array}}\times106 & \begin{array}{r@{\,±,}l} 16291.4&\phantom{0}0.9\\ -931.0&\phantom{0}5.2\\ 91.1& 12.9\\ \multicolumn{1}{r}{-10.\hphantom{00}\,}& \end{array} \\ \begin{array}{l} GM\rm Rhea\\ GM\rm Titan\\ GM\rm Hyperion\\ GM\rm Iapetus\\ \end{array} &\hspace{3ex} \begin{array}{r@{\,±,}l} 153.901 & 0.578\\ 8978.127 & 0.067\\ 0.381 & 0.011\\ 120.524 & 0.044\\ \end{array} & \begin{array}{l} \alpha\rm p \\ \delta\rm p \\ \dot{\alpha}\rm p \\ \dot{\delta}\rm p \\ \end{array} & \begin{array}{r@{\,±,}l} 40.5761 & 0.0016\\ 83.5378 & 0.0002\\ \multicolumn{1}{r}{-0.04229}& \\ \multicolumn{1}{r}{-0.00444}& \\ \end{array}\\ \noalign{\smallskip} \hline\hline \noalign{\smallskip} \multicolumn{4}{l}{GM\;units: (km^{3}sec^{-2})\hspace{3em} Saturn radius: 60330 km}\\ \multicolumn{4}{l}{Saturn pole orientation:\; \alpha\rm p,\delta\rm p(deg),\;\; \dot{\alpha}\rm p,\dot{\delta}\rm p(deg century^{-1})}\\ \end{array} \end{center}

The authors thank S. D. Gillam, W. M. Owen Jr., T-C. M. Wang, and V. Alwar (JPL) for their efforts in reducing the Cassini optical navigation data.

Previous   |   Session 5   |   Next

Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.