A non-hydrostatic rhea

Radiometric data obtained during Cassini's close flyby of Rhea, on 26 November 2005, has been subject to several published analyses aiming to determine the satellite's mass and quadrupole gravity moments. Combining aspects of two of these analyses we present our best, unbiased estimates of the gravity field parameters and point out how the constraint of hydrostatic equilibrium adopted by previous analysts affects the results. We present solutions based on a broad range of geophysical assumptions, such as the presence of degree 3 and 4 gravity field constrained at different levels. The result is a balanced approach which describes our current knowledge of Rhea's gravity field. In the case of a gravity field limited to second degree harmonics the most reliable estimates are GM = 153.9398 +/- 0.0008 km(3) s(-2), 10(6) J(2) = 931.0 +/- 12.0, 10(6) C(22) = 237.2 +/- 4.5, and 10(6) S(22) = 3.8 +/- 3.8.