Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session E6: Experimental Tests of General Relativity |
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Sponsoring Units: GGR Chair: Marc Favata, Cornell University Room: Hyatt Regency Dallas Cumberland J |
Saturday, April 22, 2006 3:30PM - 4:06PM |
E6.00001: Tests of the Gravitational Inverse-Square Law at the Dark-Energy Length Scale Invited Speaker: |
Saturday, April 22, 2006 4:06PM - 4:42PM |
E6.00002: Science, Technology and Mission Design for the Laser Astrometric Test of Relativity Invited Speaker: The Laser Astrometric Test of Relativity (LATOR) is a Michelson-Morley-type experiment designed to improve current tests of Einstein's general theory of relativity by more than four orders of magnitude. The space experiment uses laser interferometry between two laser sources placed on two small spacecraft separated by 1 degree (as seen from the Earth), whose lines of sight several times pass close by the Sun, to measure accurately the deflection of light by the solar gravitational field. The key element of the experimental design is a redundant geometry optical truss provided by a long-baseline ($\sim$100m) Michelson stellar optical interferometer that is used to measure the angle between the two spacecraft (with accuracy of 0.1 picoradian). The three arms of the light triangle formed by three space nodes are monitored with laser metrology (accurate to $\sim$1 cm). By using a combination of independent time-series of highly accurate measurements of gravitational deflection of light in the immediate proximity to the Sun, along with measurements of the Shapiro time delay on the interplanetary scales, LATOR will significantly improve our knowledge of relativistic gravity in the solar system. The experiment will measure the key post-Newtonian Eddington parameter $\gamma$ with accuracy of 1 part in $10^9$ and will also conduct a number of other unique measurements of the gravity effects on light propagation. This primary measurement pushes to unprecedented accuracy the search for cosmologically relevant scalar-tensor theories of gravity by looking for a remnant scalar field in today's solar system. LATOR will lead to very robust advances in the tests of fundamental physics: this mission could discover a violation or extension of general relativity and/or reveal the presence of an additional long range interaction in the physical law. In this talk we will discus the science, technology and mission design for the LATOR experiment. [Preview Abstract] |
Saturday, April 22, 2006 4:42PM - 5:18PM |
E6.00003: Anomalous Acceleration of Pioneer 10 and 11 Invited Speaker: Coherent radio Doppler data generated by the Deep Space Network with the Pioneer 10 and 11 spacecraft show an anomalous, constant, frequency drift that can be interpreted as an acceleration directed towards the Sun of magnitude (8.74 $\pm$ 1.33) $\times$ 10$^{-10}$ m s$^{-2}$ at distances between 20 and 70 AU (Anderson et al., {\it Phys. Rev. Lett.} {\bf 81}, 2858; Anderson et al., {\it Phys. Rev. D} {\bf 65}, 082004). Launched in 1972 and 1973 on the first mission to Jupiter, these two relatively simple spinning spacecraft are exceptionally useful as probes of solar-system gravitation. Although it is suspected that there is a systematic origin to the anomalous acceleration, none has been unambiguously demonstrated. The observational basis for the measurement and its error budget are reviewed. Then recent and ongoing data analysis is discussed, including earlier data for both spacecraft, and some sparse later data generated for Pioneer 10 between July 1998 and March 2006 at distances between 70 and 90 AU. [Preview Abstract] |
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