THE SOLAR TEST OF THE EQUIVALENCE PRINCIPLE

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