******************************************************************************
IGLOS Electronic Mail 03 Dec 14:37:33 PST 2002 Message Number 695
******************************************************************************
Author: IGLOSS-PP AC Coordinator
IGX Orbit Combination - Week 1175 (Jul 14, 2002 - Jul 20, 2002)
Contact: Robert Weber (rweber @ luna.tuwien.ac.at)
Elisabeth Fragner (efragner @ luna.tuwien.ac.at)
COMBINATION STRATEGY
--------------------
Ephemeris are combined as weighted averages computed over all centres.
Each centre and satellite is given a position weight computed from the centers
absolute deviation to the unweighted average orbit after removing small
differences in the reference frames. These weights were applied in a
second iteration to estimate Helmert transformation parameters for each
center. Finally the transformation parameters with respect to the combined
solution and the RMS of the fit are reported in Tables 2.1175.
The Earth Orientation Parameters (EOPs) are fixed to the values of the
final IGS (GPS) combination.
SOFTWARE:
---------
The GPS long arc orbit analysis software used here for individual center
ephemeris evaluation (Table 1) was developed by Beutler et al. at the
Astronomical Institute of the University of Bern (AIUB).
The weighted average (Tables 2. and 3.) software was developed by R.Weber
according to
Springer T., Beutler G., 1993, Towards an official IGS Orbit by
combining the results of IGS processing centers.
Proceedings of the IGS Workshop 1993, pp.242-249.
Beutler G., Kouba J. and T. Springer, 1995, Combining the orbits of the IGS
Analysis Centers, Bulletin Geodesique, 69, pp 200-222.
Weber R., 2000, IGS Technical Report 1999
PRODUCTS GENERATED:
-------------------
The combined IGEX-ephemerides are written to daily files in the SP3-format.
The satellite accuracy codes in the header are based on the weighted rms.
for each satellite. Note, that the result files contain all satellites
that were analysed by at least one center. We refer to the 'REMARKS' section
below, in case a satellite or center was excluded from the combination.
The following naming convention is used for the result files:
igx11750-6.sp3 IGEX Glonass ephemerides files for days 0-6
of GPS Week 1175 in the SP3 format.
igx11757.sum Combination Report for GPS Week 1175.
REMARKS concerning the IGEX Orbit Combination:
1. The satellite clock values in the combined orbit files are broadcast
clock values.
The value of 999999.999999 microseconds, according to the sp3 format
convention, is used to indicate that no clock solution is available.
2. The following orbit solutions were excluded from the combination because
they were biasing the weighted average (generally indicated by long arc RMS).
Day | Centre | SAT list
-----+--------+----------
| |
3. Until Wk 1020 the combined orbits refer to the ITRF96.
Until Wk 1142 the combined orbits refer to the ITRF97.
Since Wk 1143 the combined orbits refer to the ITRF2000.
ORBIT COMBINATION AND EVALUATION STATISTICS:
--------------------------------------------
Table 1 summarizes the statistics for a long-arc (seven days) analysis.
It gives for each satellite the position rms. for each individual center
and for the combined orbit.
Table 2 contains the transformation parameters w.r.t. the combination for
each center and each day (Tables 2.1175.0-6).
Table 3 contains the daily RMS for each satellite and center w.r.t. the
combination together with the computed satellite position RMS values
for the combined orbits (Tables 3.1175.0-6).
Table 1.1175 GPS week : 1175 MJD: 52469.0-52475.0
Long Arc Evaluation
Satellite position RMS for the individual centers' orbits
and for the combined orbit (IGX).
"E" flags eclipsing satellites.
"*" less than 7 days of data available.
"--" not (continuously) available in center solution.
Units: cm.
------------------------------
| SAT | BKG ESA MCC IGX |
------------------------------
| 3 | 5 9 11 6 |
| 5 | -- 87 -- 86 |
| 6 | 5 13 7 5 |
| 7 | 5 12 -- 6 |
| 8 | 6 99 -- 33 |
| 17 | 5 13 -- 6 |
| 18 | 14 9 -- 11 |
| 24 | 7 10 9 5 |
------------------------------
|MEDIAN| 5 13 9 6 |
------------------------------
Table 2: Daily transformation parameters w.r.t. the combined orbit.
Units: meters (DX, DY, DZ, RMS), mas (RX, RY, RZ), ppb (SCL).
Table 2.1175.0 GPS week: 1175 Day: 0 MJD: 52469
|-----------------------------------------------------|
| CENT STA| DX DY DZ RX RY RZ SCL RMS|
|-----------------------------------------------------|
| BKG 35| -.01 .00 -.04 -.18 .01 .20 -.7 .21|
| ESA 45| .02 .00 .12 .38 .00 -2.31 3.2 .51|
| MCC --| -.01 .01 -.05 .12 .05 1.45 -1.7 .19|
|-----------------------------------------------------|
Table 2.1175.1 GPS week: 1175 Day: 1 MJD: 52470
|-----------------------------------------------------|
| CENT STA| DX DY DZ RX RY RZ SCL RMS|
|-----------------------------------------------------|
| BKG 35| .00 -.01 -.08 -.10 -.12 .30 -.4 .11|
| ESA 45| .00 .02 .20 .41 .24 -1.31 2.9 .67|
| MCC --| -.01 -.01 -.08 -.01 -.09 .65 -.9 .19|
|-----------------------------------------------------|
Table 2.1175.2 GPS week: 1175 Day: 2 MJD: 52471
|-----------------------------------------------------|
| CENT STA| DX DY DZ RX RY RZ SCL RMS|
|-----------------------------------------------------|
| BKG 35| -.01 .00 -.16 -.13 -.45 -.28 -.5 .24|
| ESA 45| .01 -.01 .16 .31 .26 .16 1.4 .61|
| MCC --| -.01 -.02 -.15 -.03 -.33 -.67 -.8 .17|
|-----------------------------------------------------|
Table 2.1175.3 GPS week: 1175 Day: 3 MJD: 52472
|-----------------------------------------------------|
| CENT STA| DX DY DZ RX RY RZ SCL RMS|
|-----------------------------------------------------|
| BKG 35| -.03 .01 -.13 -.05 -.27 -.61 -.4 .34|
| ESA 45| .02 .00 .21 .07 .21 .91 .8 .47|
| MCC --| .02 -.01 -.05 .09 .19 -1.54 -.6 .14|
|-----------------------------------------------------|
Table 2.1175.4 GPS week: 1175 Day: 4 MJD: 52473
|-----------------------------------------------------|
| CENT STA| DX DY DZ RX RY RZ SCL RMS|
|-----------------------------------------------------|
| BKG 35| .00 .00 -.06 -.06 .05 -.10 -.5 .18|
| ESA 45| -.01 .00 .22 .26 .09 -.27 1.9 .43|
| MCC --| .01 .01 -.06 -.11 -.18 .50 -.7 .12|
|-----------------------------------------------------|
Table 2.1175.5 GPS week: 1175 Day: 5 MJD: 52474
|-----------------------------------------------------|
| CENT STA| DX DY DZ RX RY RZ SCL RMS|
|-----------------------------------------------------|
| BKG 35| .01 .00 -.09 -.06 .05 -.21 -.8 .18|
| ESA 45| -.01 .00 .20 .11 -.03 .90 2.4 .39|
| MCC --| .00 .00 -.05 .03 -.18 -.34 -1.3 .13|
|-----------------------------------------------------|
Table 2.1175.6 GPS week: 1175 Day: 6 MJD: 52475
|-----------------------------------------------------|
| CENT STA| DX DY DZ RX RY RZ SCL RMS|
|-----------------------------------------------------|
| BKG 35| .00 .00 -.09 -.11 .17 .55 -.6 .18|
| ESA 45| .00 .01 .25 .06 -.28 1.22 2.0 .39|
| MCC --| .01 .00 -.03 .06 -.06 -.89 -.4 .07|
|-----------------------------------------------------|
Table 3: Daily RMS difference w.r.t. combination per satellite and center.
The IGX column gives the weighted RMS of the combination
according to the accuracy codes in the SP3-file.
"E" marks eclipsing satellites.
Units: cm.
Table 3.1175.0 GPS week: 1175 Day: 0 MJD: 52469
Weighted Average
---------------------------
| SAT | BKG ESA MCC IGX |
---------------------------
| 03 | 8 9 8 6 |
| 05 | -- 0 -- 51 |
| 06 | 7 16 16 13 |
| 07 | 2 7 -- 6 |
| 08 | 36 102 -- 51 |
| 17 | 4 11 -- 6 |
| 18 | 4 11 -- 6 |
| 24 | 14 14 22 13 |
---------------------------
|Median| 7 11 16 |
---------------------------
Table 3.1175.1 GPS week: 1175 Day: 1 MJD: 52470
Weighted Average
---------------------------
| SAT | BKG ESA MCC IGX |
---------------------------
| 03 | 4 14 8 13 |
| 05 | -- 0 -- 51 |
| 06 | 3 14 17 13 |
| 07 | 1 10 -- 13 |
| 08 | 22 160 -- 51 |
| 17 | 2 16 -- 13 |
| 18 | 2 16 -- 13 |
| 24 | 5 16 18 13 |
---------------------------
|Median| 3 16 17 |
---------------------------
Table 3.1175.2 GPS week: 1175 Day: 2 MJD: 52471
Weighted Average
---------------------------
| SAT | BKG ESA MCC IGX |
---------------------------
| 03 | 5 10 6 6 |
| 05 | -- 0 -- 51 |
| 06 | 3 12 14 13 |
| 07 | 3 9 -- 6 |
| 08 | 55 153 -- 51 |
| 17 | 5 13 -- 13 |
| 18 | 4 11 -- 13 |
| 24 | 5 10 12 13 |
---------------------------
|Median| 5 11 12 |
---------------------------
Table 3.1175.3 GPS week: 1175 Day: 3 MJD: 52472
Weighted Average
---------------------------
| SAT | BKG ESA MCC IGX |
---------------------------
| 03 | 7 7 6 6 |
| 05 | -- 0 -- 51 |
| 06 | 4 11 8 6 |
| 07 | 5 8 -- 6 |
| 08 | 73 108 -- 102 |
| 17 | 7 11 -- 13 |
| 18 | 6 9 -- 6 |
| 24 | 6 8 9 6 |
---------------------------
|Median| 6 9 8 |
---------------------------
Table 3.1175.4 GPS week: 1175 Day: 4 MJD: 52473
Weighted Average
---------------------------
| SAT | BKG ESA MCC IGX |
---------------------------
| 03 | 7 15 10 13 |
| 05 | -- 0 -- 51 |
| 06 | 12 9 13 13 |
| 07 | 3 10 -- 13 |
| 08 | 37 102 -- 51 |
| 17 | 3 8 -- 6 |
| 18 | 3 8 -- 6 |
| 24 | 11 8 11 13 |
---------------------------
|Median| 7 9 11 |
---------------------------
Table 3.1175.5 GPS week: 1175 Day: 5 MJD: 52474
Weighted Average
---------------------------
| SAT | BKG ESA MCC IGX |
---------------------------
| 03 | 7 14 15 13 |
| 05 | -- 0 -- 51 |
| 06 | 6 4 9 6 |
| 07 | 4 9 -- 6 |
| 08 | 35 85 -- 51 |
| 17 | 4 8 -- 6 |
| 18 | 4 10 -- 6 |
| 24 | 9 9 10 13 |
---------------------------
|Median| 6 9 10 |
---------------------------
Table 3.1175.6 GPS week: 1175 Day: 6 MJD: 52475
Weighted Average
---------------------------
| SAT | BKG ESA MCC IGX |
---------------------------
| 03 | 7 15 7 13 |
| 05 | -- 0 -- 51 |
| 06 | 8 4 5 6 |
| 07 | 4 9 -- 6 |
| 08 | 29 72 -- 51 |
| 17 | 4 9 -- 6 |
| 18 | 4 10 -- 6 |
| 24 | 9 8 4 6 |
---------------------------
|Median| 7 9 5 |
---------------------------
End of Report: Week 1175
--
___________________________________________________________________________
Robert Weber Tel: ++43-1-58801-12865
Department of Advanced Geodesy Fax: ++43-1-58801-12896
University of Technology, Vienna E-Mail: rweber @ luna.tuwien.ac.at
Gusshausstrasse 27-29 robert.weber @ aiub.unibe.ch
A-1040 Vienna, Austria
___________________________________________________________________________