***************************************************************************=
***
dorisreport             12-Oct-2021 15:44:55 Message No 5416
***************************************************************************=
***


Author: "Lemoine, Frank G. (GSFC-61A0)" <frank.g.lemoine@nasa.gov>
Subject: Update of gscwd50 SINEX Series.


We have updated the gscwd50 SINEX series, the solution we submitted
for inclusion in ITRF2020. The weekly solutions starting
in 2008 were recomputed because some individual satellite series had
an inconsistent a priori, because they were computed with a slightly
earlier version of DPOD2014. This resulted in a linear shift for some of the
matrices in the weekly combination before the computation of the
least squares solution. To be sure that the entire
gscwd50 series was pristine, we have recomputed the solutions
and redelivered the SINEX series. In addition, we extended the
SINEX series to June 27, 2021.

A detailed technical description is available at the IDS Data Centers,
but we remind the users that this  gscwd50 series includes the
following satellites:

 SPOT-2, SPOT-3, SPOT-4, SPOT-5,
 TOPEX/Poseidon, Jason-1, Jason-2, Jason-3,
 Envisat, HY-2A, Cryosat-2, Saral.=20

Key features of this series are as follows:
I. New background gravity model used as a priori (GOCO05s). This model
   is adapted for the period prior to 2003.0 to avoid apply linear rates de=
termined
   solely over the GRACE era.
II. The SPOT-5 radial offset is adjusted weekly over the duration
     of the SPOT-5 mission.
III. We used 3.5day arcs from 1999 to 2003, instead of 7.0 day
     arcs in the previous series, for SPOT-2, SPOT-4, SPOT-5, and Envisat.
     In addition, when the solar flux was very high (> 180), we adjusted
     empirical accelerations for the along and cross track components
     every 6 hrs and with a correlation time constraint of 6 hrs as well.
     (This was tested in the series gscwd39).
IV. The elevation cutoff is 7.0 deg.
V. We apply an elevation-dependent weighting function on the DORIS data:
       1/sqrt(sin(elevation))
VI. Other features of the series implemented upon recommendation of IDS CC
   during the preparatory work on ITRF2020.
(1)We adjusted the radial offset on SPOT-2 after 2007-DOY143
(2) We adjusted the radial offset on Jason-1 over its entire data span.
(3)We add ENVISAT only after 2004-11-04, based on the performance
      of the single-satellite SINEX solutions and the recommendation=20
(4) We eliminated SPOT-4 after 2013-01-11, based on the poor performance of=
 the satellite in the single-satellite solutions after that date.=


Please do not reply directly to this message, but send 
comments and suggestions to IDS.central.bureau@cls.fr