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Testing theories of gravity in the solar system: Cassini and BepiColombo

Testing theories of gravity in the solar system: Cassini and BepiColombo. Luciano Iess Università La Sapienza IFSI/INAF. At which level is General Relativity violated?.

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Testing theories of gravity in the solar system: Cassini and BepiColombo

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  1. Testing theories of gravity in the solar system: Cassini and BepiColombo Luciano Iess Università La Sapienza IFSI/INAF

  2. At which level is General Relativity violated? • Recent theoretical developments, based upon inflationary cosmology, link the accuracy of GR to the expansion of the universe and indicate that violations may occur at levels as large as 10-5. • The theoretical uncertainties are so large that every experiment able to improve over previous tests is significant. • Violations of GR would have profound consequences in fundamental physics and cosmology.

  3. Measuring the metric tensor in the solar system. Deflection of light Solar Gravity Time delay Frequency shift = 72 km for a grazing beam  810-10 for a grazing beam

  4. SCE1 30 days continuous coverage from DSN

  5. The trajectory of Cassini in the sky during SCE1 LASCO images - SOHO

  6. B.Bertotti, L.Iess, P.Tortora: “A test of general relativity using radio links with the Cassini spacecraft” Nature, 425, 25 Sept. 2003, p. 374  = 1 +( 2.1  2.3 ) 10-5

  7. ODP pseudo X-band plasma and troposphere calibratedfrequency residuals (SCE1) rms=1.210-4 Hz Relative frequency shift rms = 1.4 10-14 Equivalent range-rate rms = 2.1 10-6 m/s Two-way Doppler frequency residuals (Hz) Dates (YY-MM-DD)

  8. Cassini Radio Science Elements (Gravity) Dedicated onboard instrumentation Ka- band ground instrumentation and media calibration system A stable platform

  9. Saturn-centered B-plane plot of the Cassini orbital solutions TCA estimate (HH.MM.SS.FF) R (Km) T (Km) TCA 1-s (seconds) From AAS paper on “Cassini navigation during solar conjunctions”P.Tortora, L.Iess, J.J. Bordi, J.E. Ekelund, D. Roth

  10. WHAT’S NEXT? FUNDAMENTAL PHYSICSAT MERCURY • PN parameter (controlling the non-linearity in the superposition of gravitational fields), from the precession of Mercury’s perihelion. • PN parameter (controlling the space curvature produced by a unit mass), from the time delay and frequency shift of radio signals. • PN parameters a1and a2(related to the existence of preferred frames of cosmological origin). • Test of theStrong Equivalence Principlethrough the Nordtvedt effect. • Flattening of the solar gravitational field (J2), from Mercury’s nodal precession. • Time variations of the gravitational “constant” G.

  11. Expected Accuracies

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