[IGSREPORT-5327] Wk 0975 GPS Earth Orientation

[IERS]

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IGS Electronic Report    Thu Sep 17 11:11:02 PDT 1998      Message Number 5327
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Author: IERS Sub-bureau for Rapid Service and Predictions
Subject: Wk 0975 GPS Earth Orientation

Subject: Earth Orientation Contributions to IERS Bulletin A
Date: 17 Sep 98


In this report, individual Earth orientation time series are compared
to the IERS Bulletin A combination.  For further information, including
the raw time series, refer to http://maia.usno.navy.mil/bulletin-a.html.

The first table below shows some comparison results for those series
included in Bulletin A during the last 30 days.  All data are aligned to
the system defined by ITRF94 and the current ICRF by removing a priori mean
bias, rate, annual and semiannual terms.  (No corrections are applied to 
the NEOS VLBI and the NEOS Intensives series for UT1-UTC.)

Units: milliseconds of arc for x, y; milliseconds of time for UT1-UTC

Contributor   Latest      #         Mean          Standard Deviation
Series         Day               (series-BullA)
                                x     y  UT1-UTC    x     y  UT1-UTC

NEOS Int.    51068.90    24                .004                .034

NEOS VLBI    51065.25     5   -.04   .15  -.003    .17   .08   .005

CSR SLR      51071.06    11   -.01   .11  -.043*   .42   .24   .077*

TUD SLR      51066.00    10    .00  -.13           .36   .17

IAA SLR      51071.00    30   -.18   .33           .13   .18

MCC SLR      51065.00    30   -.11  -.01           .27   .17

UTX LLR      51069.44     4               -.048                .159

IGS Final    51061.50    30    .00  -.01           .02   .02

IGS Rapid    51071.50    10    .07  -.06           .08   .06

             51071.50     3                .010*               .029*

USNO GPS     51071.50    14               -.002*               .018*

EMR GPS      51071.50    14                .000*               .011*

* All satellite techniques provide information on the rate of change of
  Universal Time contaminated by effects due to unmodelled orbit node
  motion.  VLBI-based results have been used to minimize drifts in UT
  estimates.


The following tables show comparisons for other related time series during
the last 30 days.  All IGS series are final solutions except for the USNO
series.  No a priori systematic corrections have been applied.

Units: milliseconds of arc for x, y; milliseconds of time for UT, LOD 

IGS           Latest   #              Mean                Standard Deviation
Series         Day               (series-BullA)
                             x     y     UT*    LOD*    x     y      UT*   LOD*

COD          51067.5  30    .33  -.06   6.51   .018    .08   .08    .24   .016

ESA          51061.5  30    .28  -.12         -.014    .20   .14          .041

EMR          51068.5  30    .20  -.01 -13.74   .017    .17   .21    .09   .030

GFZ          51061.5  30    .29  -.04   -.01   .002    .07   .05    .05   .033

JPL          51061.5  30    .25  -.03 -12.03   .015    .09   .10    .10   .047

NGS          51068.5  30    .32  -.12          .021    .17   .18          .069

SIO          51061.5  30    .32  -.02         -.008    .10   .11          .050

USN (Rapid)  51071.5  30    .21   .11          .013    .17   .19          .049

USNO GPS UT  51071.5  30                 .47                        .04

IGS Final    51061.5  30    .29  -.05    .00   .001    .05   .04    .02   .023

IGS Rapid    51071.5  30    .29  -.02    .02  -.004    .12   .09    .08   .035

* All satellite techniques provide information on the rate of change of
  Universal Time contaminated by effects due to unmodelled orbit node
  motion.  The UT results for COD and JPL are integrations of LOD estimates.
  EMR estimates UT and LOD separately by applying a priori orbit constraints.
  GFZ and IGS use VLBI-based results to minimize drifts in their UT estimates
  and thus the standard deviations are not representative of the intrinsic
  capabilities of GPS alone for monitoring UT variations.  USNO estimates
  UT using long-term models for orbit plane rotations.


IERS Central Bureau Series:

Series       Latest    #          Mean                Standard Deviation
              Day            (series-BullA)
                             x     y  UT1-UTC           x     y  UT1-UTC

Bulletin B   51029.   30    .19   .07   .011           .04   .08   .030

97C04        51070.   30    .12   .17   .004           .09   .14   .036


Plots of the residuals are available at http://maia.usno.navy.mil/plots.html.
------------------------------------------------------------------------------
The IERS Sub-bureau for Rapid Service and Prediction is an activity of the
National Earth Orientation Service and is performed by the Earth Orientation
Department at the U.S. Naval Observatory.
--
Dennis D. McCarthy                       dmc at maia.usno.navy.mil
Director, Directorate of Time            phone: (202) 762-1837
U.S. Naval Observatory                   fax: (202) 762-1563
Washington, DC 20392-5420


[Mailed From: Dennis McCarthy <dmc at maia.usno.navy.mil>]