Tempo: Determining, Combining, and Predicting Earth Orientation Parameters for Spacecraft Navigation

Abstract

In support of spacecraft tracking and navigation at the Jet Propulsion Laboratory (JPL), Earth orientation measurements are currently acquired, processed, and delivered twice-per-week to the JPL navigation teams by the Time and Earth Motion Precision Observations (TEMPO) project. Because the Earth’s orientation changes rapidly and unpredictably, measurements must be acquired frequently and processed rapidly in order to meet the near-real-time Earth orientation calibration requirements of the navigation teams. These requirements are currently met by (1) conducting twice-per-week single baseline VLBI observing sessions; (2) rapidly processing the VLBI data to determine the baseline variation-of-latitude and UTO components of the Earth’s orientation; and (3) using the Kaiman Earth Orientation Filter (KEOF) to combine the TEMPO VLBI measurements with other publicly available Earth orientation measurements, including determinations and forecasts of the axial component of the atmospheric angular momentum (AAM), in order to generate and deliver the Earth orientation calibrations (polar motion and UT1) required by the navigation teams.