Long-range tests of the equivalence principle

The equivalence principle can be tested using accurate tracking of the Moon, planets, and interplanetary spacecraft. Tests with solar system bodies probe the dependence of the equivalence principle on self-energy. Analysis of lunar laser ranges yields the difference in the ratio of the gravitational and inertial masses for the Earth and Moon of ({-0.7}±1.5)×10-13. In conjunction with laboratory tests of the equivalence principle and spacecraft and VLBI tests of PPN γ, one derives |β-1|⩽0.0005. Planetary tests are feasible, in particular tests using Mars. Improvements in Doppler accuracies under development may allow tests with interplanetary spacecraft.