[IGSREPORT-5278] Wk 0973 GPS Earth Orientation

[IERS]

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IGS Electronic Report    Fri Sep  4  5:50:41 PDT 1998      Message Number 5278
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Author: IERS Sub-bureau for Rapid Service and Predictions
Subject: Wk 0973 GPS Earth Orientation

Subject: Earth Orientation Contributions to IERS Bulletin A
Date:  3 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.    51054.78    24                .010                .030

NEOS VLBI    51051.18     5    .04   .21  -.003    .08   .06   .005

CSR SLR      51056.25    11    .11   .05   .028*   .59   .24   .073*

TUD SLR      51051.00    10   -.23  -.24           .27   .37

IAA SLR      51056.00    30   -.21   .37           .13   .18

MCC SLR      51051.00    30   -.32  -.06           .20   .31

UTX LLR      51057.17     2                .016                .007

IGS Final    51047.50    30    .00  -.02           .02   .03

IGS Rapid    51057.50    10    .00  -.03           .04   .03

             51057.50     3               -.016*               .005*

USNO GPS     51056.50    14                .001*               .019*

EMR GPS      51057.50    15               -.002*               .019*

* 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          51052.5  30    .31  -.07   6.76   .004    .10   .07    .07   .015

ESA          51047.5  30    .19   .07         -.010    .29   .19          .035

EMR          51047.5  30    .30   .04 -13.41   .015    .12   .21    .18   .030

GFZ          51047.5  30    .35  -.04   -.03   .014    .06   .06    .03   .030

JPL          51047.5  30    .26  -.04 -11.75   .028    .08   .09    .27   .035

NGS          51051.5  30    .36  -.03          .001    .22   .19          .063

SIO          51047.5  30    .33  -.05         -.005    .07   .10          .040

USN (Rapid)  51057.5  30    .18   .05          .002    .10   .15          .041

USNO GPS UT  51056.5  29                 .52                        .09

IGS Final    51047.5  30    .30  -.05    .00   .000    .04   .05    .02   .022

IGS Rapid    51057.5  30    .27   .00    .05  -.012    .11   .08    .07   .027

* 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   .08   .008           .03   .05   .029

97C04        51054.   30    .17   .12  -.001           .06   .09   .036


Plots of the residuals are available at http://maia.usno.navy.mil/plots.html.
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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>]