THE MASSES OF URANUS AND ITS MAJOR SATELLITES FROM VOYAGER TRACKING DATA AND EARTH-BASED URANIAN SATELLITE DATA

Analysis of the Doppler-tracking data and star-satellite imaging from the Voyager 2 spacecraft combined with Earth-based astrometric satellite observations has yielded improved values for the masses of the Uranian system and the satellites Ariel, Umbriel, Titania, Oberon, and Miranda. The present results are consistent with those previously published-Tyler et al. [Science, 233, 79 (1986)], Anderson et al. [J. Geophys. Res., 92, 14877 (1987)], Laskar & Jacobson [A&A, 188, 212 (1987)], Brown et al. [Uranus, p. 513 (1991)]. Masses are expressed as the product GM, the universal gravitational constant G times the mass M of the body, in units of (km3 s-2). The satellite masses are (4.4 +/- 0.5) for Miranda, (90.3 +/- 8.0) for Ariel, (78.2 +/- 9.0) for Umbriel, (235.3 +/- 6.0) for Titania, and (201.1 +/- 5.0) for Oberon. The mass of the Uranian system is (5 794 548.6 +/- 7.0) and the ratio of the mass of the Sun to the mass of the Uranian system is (22 902.982 +/- 0.028). Quoted errors are standard errors and are our assessment of the true rather than the formal errors. The Uranus rotational pole orientation angles and gravity harmonic coefficients were fixed at the values determined by French et al. [Icarus, 73, 349 (1988)] from stellar occultations of the Uranian rings observed from both the Earth and Voyager 2 and from the occultation of the spacecraft radio signal.