We improve, using a larger set of observations including Voyager 2 Neptune flyby data, previous bounds on the amount of dark matter (DM) trapped in a spherically symmetric distribution about the sun. We bound DM by noting that such a distribution would increase the effective mass of the sun as seen by the outer planets and by finding the uncertainty in that effective mass for Uranus and Neptune in fits to the JPL Developmental Ephermeris residuals, including optical data and those two planets' Voyager 2 flybys. We extend our previous procedure by fitting more parameters of the developmental ephemerides. Additionally, we present here the values for Pioneer 10 and 11 and Voyager 1 and 2 Jupiter ranging normal points (and incorporate these data as well). Our principal result is to limit DM in spherically symmetric distributions in orbit about the sun interior to Neptune's orbit to less than an earth mass and interior to Uranus' orbit to about 1/6 of an earth's mass.
A new test of the isotropy of the one-way velocity of light has been performed using NASA's Deep Space Network (DSN). During five rotations of the Earth, we compared the phases of two hydrogen-maser frequency standards separated by 21 km using an ultrastable fiber optics link. Because of the unique design of the experiment, it is possible to derive independent limits on anisotropies that are linear and quadratic in the velocity of the Earth with respect to a preferred frame. Assuming that the anisotropies have not been partially canceled by systematic environmental effects on the instrumentation, the best limits that can be inferred from the data are AC/C < 3.5 x lo-' and Ac/c < 2x l o -* for linear and quadratic dependencies, respectively, on the velocity of the Earth with respect to the cosmic microwave background. The theoretical interpretation of the experiment is discussed.
Earth gravity assist, we regularly obtained frequency measurements of the spacecraft clock-an ultrastable crystal oscillator (USO) supplied by Frequency Electronics, Inc. The solar gravitational redshift in frequency was readily detectable, and because of the unique variations in heliocentric distance we could separate the general relativistic effects from the USO's intrinsic frequency variations. We have verified the total frequency shift predicted by general relativity to 0.5% accuracy, and the solar gravitational redshift to 1% accuracy. This is the first test of the solar redshift with an interplanetary spacecraft.
A derivation of the gravitational redshift effect to order c 4 is presented. The calculation is performed within the framework of the parametrized post-Newtonian formalism for analyzing metric theories of gravity, which includes corrections to second order in the Newtonian potential, gravitomagnetic contributions, and preferred-frame terms. We briefly discuss how to generalize our results to include possible violations of local Lorentz invariance or local position invariance which can arise in nonmetric theories. Our results are useful for analyzing possible new redshift experiments which may be sensitive to second-order effects, such as a space mission involving a close solar flyby.
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