Galileo gravity results and the internal structure of Io

Science

Volumn 272, Issue 5262, 1996, Pages 709-712

  Anderson, J D ^a   Sjogren, W L ^a   Schubert, G ^b  

^a CALIFORNIA INSTITUTE OF TECHNOLOGY   (United States)

^b UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

DOPPLER DATA; GALILEO; GRAVITATIONAL FIELD; METALLIC CORE; PLANETARY SATELLITE;

IO;

EID: 0029767551     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.272.5262.709     Document Type: Article

References (26)

1. For a description of Io and other Jupiter satellites, see D Morrison, Ed., Satellites of Jupiter(Univ of Arizona Press, Tucson, 1982): J. A. Burns and M S Matthews, Eds., Satellites (Univ of Arizona Press, Tucson, 1986).
2. For a description of Io and other Jupiter satellites, see D Morrison, Ed., Satellites of Jupiter(Univ of Arizona Press, Tucson, 1982): J. A. Burns and M S Matthews, Eds., Satellites (Univ of Arizona Press, Tucson, 1986).
3. An overview of the Galileo mission, including a description of the spacecraft configuration (orbiter and probe), can be found in T. V. Johnson and C. M. Yeates, Space Sci. Rev 60, 3 (1992).
4. 1/2, consistent with our data analysis
5. 1/2, consistent with our data analysis
6. We have placed the data in the public domain by transferring all data files used in our analysis to nine-track magnetic tape and sending copies to the National Space Science Data Center, Goddard Space Flight Center
7. -1 for both USO data and coherent Doppler data sampled at 60 s. For the 2 hours of USO data sampled at 10 s, the 1σ error was increased by a factor of √6. An ODP algorithm, applied automatically, increased the Doppler error at lower elevation angles with respect to the station's horizon
8. -1 for both USO data and coherent Doppler data sampled at 60 s. For the 2 hours of USO data sampled at 10 s, the 1σ error was increased by a factor of √6. An ODP algorithm, applied automatically, increased the Doppler error at lower elevation angles with respect to the station's horizon
9. 22 give the contributions to the gravitational potential of the spherical harmonics of degree / and order m for l = 2, m = 0 and l = 2, m = 2, respectively.
10. 22), were fixed at zero. We justified setting them to zero by obtaining a few fits to the Doppler data with other second-degree and -order and third-degree and -order coefficients. Our interpretation of these fits indicated that the amplitudes of nonhydrostatic components were no greater than that of noise.
11. A celestial mechanics experiment, similar to the Galileo experiment discussed here, was included on Pioneer 10 and 11 but not on Voyager. Previous results on the gravitational field of the Jupiter system can be found in G. W. Null, J. D. Anderson, S. K. Wong, Science 188, 476 (1975), J. D. Anderson, in Jupiter, T. Gehrels, Ed. (Univ. of Arizona Press, Tucson, 1976), pp 113-121; G. W. Null, Astron J 81, 1153 (1976); J. K. Campbell and S. P. Synnott, ibid. 90, 364 (1985). Because of the close Galileo flybys of Io and Europa, our recommended standard errors are considerably smaller than earlier realistic errors
12. A celestial mechanics experiment, similar to the Galileo experiment discussed here, was included on Pioneer 10 and 11 but not on Voyager. Previous results on the gravitational field of the Jupiter system can be found in G. W. Null, J. D. Anderson, S. K. Wong, Science 188, 476 (1975), J. D. Anderson, in Jupiter, T. Gehrels, Ed. (Univ. of Arizona Press, Tucson, 1976), pp 113-121; G. W. Null, Astron J 81, 1153 (1976); J. K. Campbell and S. P. Synnott, ibid. 90, 364 (1985). Because of the close Galileo flybys of Io and Europa, our recommended standard errors are considerably smaller than earlier realistic errors
13. A celestial mechanics experiment, similar to the Galileo experiment discussed here, was included on Pioneer 10 and 11 but not on Voyager. Previous results on the gravitational field of the Jupiter system can be found in G. W. Null, J. D. Anderson, S. K. Wong, Science 188, 476 (1975), J. D. Anderson, in Jupiter, T. Gehrels, Ed. (Univ. of Arizona Press, Tucson, 1976), pp 113-121; G. W. Null, Astron J 81, 1153 (1976); J. K. Campbell and S. P. Synnott, ibid. 90, 364 (1985). Because of the close Galileo flybys of Io and Europa, our recommended standard errors are considerably smaller than earlier realistic errors
14. A celestial mechanics experiment, similar to the Galileo experiment discussed here, was included on Pioneer 10 and 11 but not on Voyager. Previous results on the gravitational field of the Jupiter system can be found in G. W. Null, J. D. Anderson, S. K. Wong, Science 188, 476 (1975), J. D. Anderson, in Jupiter, T. Gehrels, Ed. (Univ. of Arizona Press, Tucson, 1976), pp 113-121; G. W. Null, Astron J 81, 1153 (1976); J. K. Campbell and S. P. Synnott, ibid. 90, 364 (1985). Because of the close Galileo flybys of Io and Europa, our recommended standard errors are considerably smaller than earlier realistic errors
15. B. D. Tapley, in Recent Advances in Dynamical Astronomy, B. D. Tapley and V. Szebehely, Eds (Reidel, Dordrecht, 1973), pp 396-425
16. 4 for Jupiter, and the right ascension and declination of Jupiter's pole. He made small corrections to the five GM values but left the Jupiter gravity parameters and the pole position unchanged from their spacecraft flyby values. The fitting model was fully relativistic, consistent with the ODP Relativistic terms in the satellite orbits are important for consistency but are too small to provide tests of general relativity.
17. E.R Cohen and B. N Taylor, Rev Mod. Phys. 57, 1121 (1987).
18. -3 Hz; however, it was too optimistic for the lower frequency Jupiter mass signal. We therefore retained the formal errors for the satellite gravity parameters but increased the formal Jupiter mass error by a factor of 3. Consequently, all errors adopted for this report were our best estimates of realistic standard error
19. For example, W M. Kaula, An Introduction to Planetary Physics. The Terrestrial Planets (Wiley, New York, 1968), W. B Hubbard and J. D Anderson, Icarus 33, 336 (1978), S. F. Dermott, ibid. 37, 310 (1979), V N. Zharkov, V. V Leontjev, A. V Kozenko, ibid 61, 92 (1985).
20. For example, W M. Kaula, An Introduction to Planetary Physics. The Terrestrial Planets (Wiley, New York, 1968), W. B Hubbard and J. D Anderson, Icarus 33, 336 (1978), S. F. Dermott, ibid. 37, 310 (1979), V N. Zharkov, V. V Leontjev, A. V Kozenko, ibid 61, 92 (1985).
21. For example, W M. Kaula, An Introduction to Planetary Physics. The Terrestrial Planets (Wiley, New York, 1968), W. B Hubbard and J. D Anderson, Icarus 33, 336 (1978), S. F. Dermott, ibid. 37, 310 (1979), V N. Zharkov, V. V Leontjev, A. V Kozenko, ibid 61, 92 (1985).
22. For example, W M. Kaula, An Introduction to Planetary Physics. The Terrestrial Planets (Wiley, New York, 1968), W. B Hubbard and J. D Anderson, Icarus 33, 336 (1978), S. F. Dermott, ibid. 37, 310 (1979), V N. Zharkov, V. V Leontjev, A. V Kozenko, ibid 61, 92 (1985).
23. -3 These values and their estimated uncertainties are consistent with Table 2.
24. M. Segatz, T. Spohn, M N. Ross, G. Schubert, Icarus 75, 187 (1988); M. Wienbruch and T. Spohn, Planet. Space Sci. 43, 1045 (1995)
25. M. Segatz, T. Spohn, M N. Ross, G. Schubert, Icarus 75, 187 (1988); M. Wienbruch and T. Spohn, Planet. Space Sci. 43, 1045 (1995)
26. This experiment was coordinated at JPL by the Galileo Radio Science Support Team (R. G. Herrera, team leader) The radio Doppler data were generated with the support of the Office of Tracking and Data Acquisition and the DSN. The data analysis depended on the availability of software and personnel of the Galileo Project Navigation Team (W E Kirhofer, team leader). We thank all concerned for their help and advice. We also thank E. L. Lau for generating plots from ODP computer files. The research described here was carried out by JPL, California Institute of Technology, and was sponsored by the Galileo Project through an agreement with the National Aeronautics and Space Administration