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J.D. Anderson, E.L. Lau (JPL), G. Schubert, J.L. Palguta (UCLA)
Gravity science is a major component of the JUNO Mission, one of two selected by NASA for detailed study as a candidate for the next mission in the New Frontiers Program. The plan for JUNO is to insert a spinning spacecraft into an eccentric orbit with period of about 11 days and a periapse only a few thousand kilometers above Jupiter's surface. On each of a possible 32 orbits, the Jovian gravitational field is accessible for an observing interval of plus and minus six hours from closest approach. On each observing run, multi-link radio Doppler data are generated by the Deep Space Network (DSN) in the X-Band (~8.4 GHz) and Ka-Band (~34.3 GHz). This produces Doppler velocity measurements to an accuracy of about 0.005 mm/s at a sample interval of 60 s. We propose a gravity inversion technique that can yield an accuracy of 10-9 for lower degree normalized zonal harmonics through degree six, providing information on Jupiter's core, and higher degree harmonics, especially degree 12 through 30, can be measured to an accuracy of about 10-8. The requirement on the gravity measurements for a discrimination between solid-body rotation and rotation in deep zonal flows has been discussed by Hubbard (Icarus 137 357). The proposed inversion technique meets this requirement. In addition, over the total time interval of 32 orbits, or about one year, the polar precession rate can possibly be measured, and tides raised by the five Jovian satellites JI to JV, as reflected in the gravity data, can yield information on Jupiter's Love numbers kn at five different depths in the atmosphere.
The JPL contribution to this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. G.S. and J.L.P acknowledge support by grants from NASA through the Planetary Geology and Geophysics program.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.