Titan's Gravitational Field

Titan's gravitational field is inferred from an analysis of archived radio Doppler data for six Cassini flybys. The analysis considers each flyby separately in contrast to the approach of lumping all the data together in a massive inversion. In this way it is possible to gain an improved understanding of the character of each flyby and its usefulness in constraining the gravitational coefficient C₂₂ . Though our analysis is not yet complete and our final determination of C₂₂ could differ from the result we report here by 1 or 2 sigma, we find a best-fit value of C₂₂ equal to (13.21 × 0.17) × 10^-6, significantly larger than the value of 10.0 × 10^-6 obtained from an inversion of the lumped Cassini data. We also find no determination of the tidal Love number k₂. The larger value of C₂₂ implies a moment of inertia factor equal to 0.3819 × 0.0020 and a less differentiated Titan than is suggested by the smaller value. The larger value of C₂₂ is consistent with an undifferentiated model of the satellite. While it is not possible to rule out either value of C₂₂ , we prefer the larger value because its derivation results from a more hands on analysis of the data that extracts the weak hydrostatic signal while revealing the effects of gravity anomalies and unmodeled spacecraft accelerations on each of the six flybys.