Testing Gravitational Time Delay Predictions of General Relativity测试广义相论引力时延预测.pptVIP

Measurement of the Gravitational Time Delay Using Drag-Free Spacecraft and an Optical Clock Mission Concept Outline Motivation for proposed mission Description of mission Orbits optical clocks drag-free capabilities uncertainty analysis results of analysis Motivation Proposed mission design Spacecraft clock noise Drag-free spacecraft Shapiro time delay (Log term) Gravitational Time Delay Noise Analysis The function Changes in the round-trip travel time Simulations including the effects oforbit determination uncertainties Additional science measurements-gravitational frequency shifts Conclusions References Epoch determination Summary of contributions to uncertaintyin g * Neil Ashby, Dept. of Physics, UCB 390, University of Colorado, Boulder, CO 80309-0390. e-mail: ashby@boulder.nist.gov Peter Bender, JILA, Boulder, CO Scott Diddams, NIST, Boulder, CO Steve Jefferts, NIST, Boulder, CO Nathan Newbury, NIST, Boulder, CO Chris Oates, NIST, Boulder, CO Tests of Gravity Workshop Cleveland, OH May 19-21, 2009 OBJECTIVE: measure g to 10-8 It is important to test Gravitational Theories—General Relativity in particular— wherever they can be tested. Accurate measurement of time delay is a promising method for detecting possible deviations from General Relativity (GR). Some scalar-tensor extensions of GR predict deviations from general relativity in the range The best measurement of g came from the Cassini mission: (Bertotti, Iess, Tortora, Nature 425, 374 (2003). Two-way measurements between a “near” spacecraft orbiting at the L-1 point, 1.5 million km from earth, and a distant spacecraft in the ecliptic plane, with orbital period 2 years and eccentricity 0.37. Solar conjunctions occur 1, 3, 5 years after launch. The most accurate time delay measurements are assumed to be made over roughly 8 day time periods around each solar conjunction. Nearly continuous measurements over longer periods are expected to improve the accuracy for g by