Timothy P. Krisher

Voyager 2 Test Of The Radar Time-Delay Effect

By analyzing radio range measurements generated during the solar conjunction of the Voyager 2 spacecraft in 1985, the relativistic time-delay effect has been tested accurately with a spacecraft at a distance of 3 x 10 to the 9th km from the earth. Because the range measurements were generated simultaneously at two frequencies on the downlink, it was possible to derive calibrations for the delay resulting from intervening solar plasma. In addition, a record of attitude thruster firings was used to model small accelerations of the spacecraft that could have produced a range error. It was thereby possible to determine the parameterized post-Newtonian parameter gamma to an accuracy of 3 percent with only a sparse amount of range data.

A POTENTIAL NEW TEST FOR UNSEEN MATTER IN THE OUTER SOLAR SYSTEM

The recent development of trapped-ion frequency standards, which offer high stability over long time periods, provides us with a potential new method for detecting unseen matter in the outer solar system. A distribution of matter or a planetary body could produce a measurable gravitational redshift of the radio signal received from a spacecraft equipped with an ultrastable frequency standard. Trapped-ion standards have a potential frequency stability of 1 part in 10(exp 16) or better over long time periods (greater than 10(exp 6) s). We consider the potential improvements this method could yield over conventional dynamical tests for unseen matter in the outer solar system possible now or anticipated in the near future.