[IGSREPORT-5298] Wk 0974 GPS Earth Orientation

[IERS]

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IGS Electronic Report    Thu Sep 10 13:12:49 PDT 1998      Message Number 5298
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Author: IERS Sub-bureau for Rapid Service and Predictions
Subject: Wk 0974 GPS Earth Orientation

Subject: Earth Orientation Contributions to IERS Bulletin A
Date: 10 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.    51060.76    24                .015                .023

NEOS VLBI    51058.25     5    .05   .18  -.002    .10   .12   .007

CSR SLR      51060.11    11    .04   .13  -.093*   .49   .16   .186*

TUD SLR      51060.00    10   -.09  -.10           .32   .22

IAA SLR      51063.00    30   -.17   .35           .13   .19

MCC SLR      51058.00    30   -.35  -.10           .20   .27

UTX LLR      51057.17     2               -.018                .149

IGS Final    51054.50    30    .00  -.02           .03   .03

IGS Rapid    51064.50    10    .00  -.02           .07   .03

             51064.50     4               -.010*               .016*

USNO GPS     51063.50    14               -.005*               .018*

EMR GPS      51064.50    15               -.006*               .034*

* 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          51060.5  30    .33  -.07   6.66   .010    .10   .07    .17   .015

ESA          51054.5  30    .29  -.06         -.012    .25   .18          .041

EMR          51061.5  30    .22   .01 -13.64   .017    .16   .22    .13   .030

GFZ          51061.5  30    .30  -.03   -.01   .002    .07   .05    .04   .031

JPL          51054.5  30    .24  -.05 -11.92   .016    .09   .09    .18   .045

NGS          51058.5  30    .32  -.06          .006    .20   .15          .074

SIO          51054.5  30    .33  -.02         -.013    .09   .11          .044

USN (Rapid)  51063.5  30    .17   .08          .011    .13   .15          .050

USNO GPS UT  51063.5  29                 .48                        .05

IGS Final    51054.5  30    .30  -.05    .00   .000    .05   .05    .01   .022

IGS Rapid    51064.5  30    .27   .00    .03  -.004    .12   .08    .08   .033

* 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   .008           .04   .06   .031

97C04        51065.   30    .16   .12   .036           .07   .14   .068


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>]