Allan Variance in Earth rotation time series

Allan Variance is currently used in Time frequency metrology for estimation of the stability of primary frequency standards. It is also applied in the time domain for characterization of the stability of atomic clocks or atomic time scales. More recently, the Allan Variance analysis was applied to the field of Earth Orientation metrology. At first it can be used to characterize at various time scales, the internal noise of the time series describing the Earth Rotation variations that are derived from the different geodetic techniques like Laser Ranging to artificial Satellites (SLR), Very Large Baseline Interferometry (VLBI) and GPS. In these series much of the noise is white phase noise or flicker phase noise. The uncertainties given for the various series are derived, from the data analysis and generally do not correspond to the "true" precision. A second application of the Allan Variance as a statistical tool is to intercompare these series and their internal precision in order to give them a proper weight for their general combination. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.