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J. Aiello (JPL/CalTech)
The primary goals of a Europa orbiter mission will be to acquire high resolution global surface maps from low altitude and an accurate measurement of Europa's gravitational potential. Global surface mapping requires high inclination orbits, and gravity mapping is best accomplished by tracking the spacecraft, unperturbed by propulsive maneuvers, for a period of time of at least one complete orbit of Europa about Jupiter. Studies have shown, however, that low-altitude orbits with inclinations greater than ~45o above the equatorial plane are unstable and would therefore likely require frequent orbit maintenance maneuvers (perhaps as often as once per day). This maneuver activity would hinder measurements of the gravity field.
Analytic methods employing the Hill approximation have recently identified regions of relative stability about Europa in terms of orbit inclination, argument of periapse, and eccentricity. The work described here offers a detailed look at trajectories in these regions. Direct numerical integrations of low altitude orbits have been performed for sets of initial conditions acceptable for mapping orbits. Galilean satellite ephemerides, gravitational harmonics, and solar radiation pressure are modeled. A range of trajectories that could satisfy both mission goals are indicated. Characteristics of specific trajectories are presented with implications for science planning and operations.
The author(s) of this abstract have provided an email address for comments about the abstract: jaiello@jpl.nasa.gov
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.