THE DIPOLE OBSERVED IN THE COBE DMR 4 YEAR DATA

The largest anisotropy in the cosmic microwave background (CMB) is the approximate to 3 mK dipole assumed to be due to our velocity with res pect to the CMB. Using the 4 year data set from all six channels of th e COBE Differential Microwave Radiometers (DMR), we obtain a best-fit dipole amplitude 3.358+/-0.001+/-0.023 mK in the direction (l, b)=(264 .degrees 31+/-0.degrees 04+/-0.degrees 16, +48.degrees 05+/-0.degrees 02+/-0.degrees 09), where the first uncertainties are statistical. and the second include calibration and combined systematic uncertainties. This measurement is consistent with previous DMR and FIRAS results.