Updating Terrestrial Reference Frame using Sequential Computation Method

JTRF2020 is a recent contribution by NASA Jet Propulsion Laboratory to IERS as part of their effort to determine ITRF2020.  JTRF2020 is estimated daily using a sequential computational method (called "SREF") based on the SRIF and DMCS algorithms which are respective variants of the Kalman filter and smoother.  The filtering algorithm allows us to make timely update of the reference frame, as newer geodetic analysis data become available beyond those ingested into JTRF2020.  Benefits of such frame updating are examined using hindcasting experiments, which are presented here.  Also, some of the standard formulas used in terrestrial reference frame realizations are not immediately suitable for sequential formulation required by the algorithms like the Kalman filter.  We thus describe our sequential re-formulation of these formulas, including the intrinsic constraints, week-long EOP arcs, and lack of initial conditions.