The solar test of the equivalence principle

The Earth-Mars-Sun-Jupiter system allows for a sensitive test of the strong equivalence principle (SEP) that is qualitatively different from that provided by lunar laser ranging. Using analytic and numerical methods, we demonstrate that Earth-Mars ranging can provide a useful estimate of the SEP parameter eta. Two estimates of the predicted accuracy are derived and quoted, one based on conventional covariance analysis, and another (called ''modified worst case'' analysis) that assumes that systematic errors dominate the experiment. If future Mars missions provide ranging measurements with an accuracy of sigma meters, after 10 years of ranging the expected accuracy for the SEP parameter eta will be of order (1-12) x 10(-4)sigma. These ranging measurements will also provide the most accurate determination of the mass of Jupiter, independent of the SEP-effect test.