Measurement of the de Sitter Precession of the Moon: A Relativistic Three-Body Effect

We analyzed lunar laser-ranging data, accumulated between 1970 and 1986, to estimate the deviation of the precession of the Moon's orbit from the predictions of general relativity. We found no deviation from this predicted de Sitter precession rate of nearly 2 angular sec per century (sec/cy), to within our estimated standard error of 0.04 sec/cy. This standard error, 2% of the predicted effect, incorporates our assessment of the likely contributions of systematic errors, and is about threefold larger than the statistical standard error.