A KALMAN-FILTER-BASED APPROACH TO COMBINING INDEPENDENT EARTH-ORIENTATION SERIES

An approach, based upon the use of a Kalman filter, that is currently employed at the Jet Propulsion Laboratory (JPL) for combining independ ent measurements of the Earth's orientation, is presented. Since chang es in the Earth's orientation can be described as a randomly excited s tochastic process, the uncertainty in our knowledge of the Earth's ori entation grows rapidly in the absence of measurements. The Kalman-filt er methodology allows for an objective accounting of this uncertainty growth, thereby facilitating the intercomparison of measurements taken at different epochs (not necessarily uniformly spaced in time) and wi th different precision. As an example of this approach to combining Ea rth-orientation series, a description is given of a combination, SPACE 95, that has been generated recently at JPL.