[IGSREPORT-4825] Wk 0954 GPS Earth Orientation

[IERS]

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IGS Electronic Report    Thu Apr 23 12:54:56 PDT 1998      Message Number 4825
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Author: IERS Sub-bureau for Rapid Service and Predictions
Subject: Wk 0954 GPS Earth Orientation

Subject: Earth Orientation Contributions to IERS Bulletin A
Date: 23 Apr 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.    50916.65    21                .004                .018

NEOS VLBI    50918.25     4   -.08   .04   .006    .19   .11   .010

CSR SLR      50915.70    11   -.14  -.39  -.085*   .35   .24   .127*

TUD SLR      50919.00    10   -.16  -.20           .55   .57

IAA SLR      50924.00    30   -.03  -.17           .23   .15

MCC SLR      50919.00    10    .00  -.12           .29   .33

UTX LLR      50918.38    11                .054                .083

IGS Final    50914.50    30    .00   .02           .04   .03

IGS Rapid    50924.50    10    .04   .05           .09   .11

             50924.50     7               -.028*               .054*

USNO GPS     50924.50    15               -.003*               .023*

* 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          50921.5  30    .36  -.05   7.55   .022    .05   .07    .20   .014

ESA          50914.5  30    .33   .01         -.031    .18   .10          .027

EMR          50921.5  30   -.20   .44 -11.46  -.018    .17   .13    .06   .034

GFZ          50921.5  30    .36  -.02    .03  -.027    .10   .10    .17   .026

JPL          50914.5  30    .28  -.12  -8.05   .021    .11   .10    .23   .039

NGS          50916.5  30    .49   .04         -.030    .21   .22          .041

SIO          50914.5  30    .27  -.09          .019    .15   .19          .039

USN (Rapid)  50924.5  30    .19   .21         -.022    .15   .22          .052

USNO GPS UT  50924.5  30                 .34                        .10

IGS Final    50914.5  30    .30  -.02    .01  -.006    .07   .05    .02   .020

IGS Rapid    50924.5  30    .31   .07    .10  -.016    .12   .12    .07   .023

* 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 UT estimates.
  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   50874.   30    .09   .18   .005           .14   .11   .036

97C04        50924.   30    .16   .03   .002           .12   .08   .044


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>]