[IGSREPORT-0910] IGS Final Orbit Comb(735)
Analysis
Analysis
Wed Apr 20 11:44:06 PDT 1994
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IGS Electronic Report Wed Apr 20 11:44:06 PDT 1994 Message Number 0910
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Author: Analysis Centres Coordinator / Geodetic Survey of Canada
Subject: IGS Final Orbit Comb(735)
IGS Final Orbit Combination Week 0735 (Feb 06, 1994 - Feb 12, 1994)
Contacts: F. Lahaye (lahaye at geod.emr.ca), J. Kouba (kouba at geod.emr.ca)
COMBINATION STRATEGY:
For a complete description of combination strategy, please refer to the report
posted on CDDIS (IGS07357.SUM).
SOFTWARE:
The weighted average software used was developed by T. Springer and G. Beutler
during 1993. The GPS long arc orbit analysis software used here for individual
centre ephemeris evaluation was developed by Beutler et al. at the Astronomical
Institute of the University of Bern (AIUB). For more details on the orbit
combination and complete references for both software see:
Beutler, Kouba, Springer, 1993, Combining orbits of the IGS processing
centres, in IGS Analysis Centre Workshop, October 12-14, Ottawa, pp 19-55.
PRODUCTS GENERATED:
The resulting average ephemeris and clocks are output to daily files in SP3
format. The satellite accuracy codes displayed in the header are based on the
weighted RMS for each satellite. Note that each file contains all the
satellites that appear in any of the centre ephemeris files. If a satellite or
centre was excluded from combination, a note in the REMARKS section of this
report will identify the exclusion and the reason.
The IGS Final Orbit files generated and uploaded into CDDIS @ NASA/GSFC are:
IGS07350-6.SP3 IGS GPS ephemeris files for days 0-6, week 0735 in SP3 format.
IGS07357.ERP Earth rotation parameters (ERP) associated with ephemerides.
IGS07357.SUM Complete report.
The old Rapid Service files have been renamed to:
IGR07350-6.SP3 Rapid Service ephemeris files for days 0-6.
IGR07357.ERP Rapid Service earth rotation parameters (ERP).
IGR07357.SUM Rapid Service complete report.
REMARKS on IGS Final Orbit Combination:
1. Only the GFZ "exact" clock corrections (one epoch out of two) are included
in the combination and RMS computation (no "interpolation" values).
2. The large clock correction RMS for COD on day 3 (Feb 9), 5 and 6 (Feb 11-12)
are due to clock shifts for PRN03 that were likely not acknowledge by
broadcast message but observed by all centres. These broadcast clock
corrections were therefore not used in the estimation of the initial GPS
time aligmnent parameters.
3. Several clock solutions were excluded from combination due to large clock
shifts or outliers but were kept for RMS computation. The following table
lists the exclusions:
Day (Date) | PRN | Centres | Shift/Outliers
-----------+---------+---------+---------------
0 (Feb 06) | All | EMR | Noise ~100ns.
2 (Feb 08) | All | EMR | Moise ~100ns.
4. There was a maneuvre of PRN22 on day 3 (Feb 9) (ref. NANU 041-94038). The
ESA solution which modeled the maneuvre is provided for that satellite on
that day as the combined solution. An associated accuracy code of 0
(unknown) was given since there was no redundancy. The NGS and SIO solutions
for PRN22 on the day of maneuvre were excluded from combination based on the
assumption that they are extrapolation instead of actual modeling.
5. A state vector reset was modeled for PRN22 on day 3 (Feb 9) for all centres.
6. Several other orbit solutions were excluded from combination because they
were driving the weighted average out (based on long arc RMS). These were
still used for statistics computation. The following table lists the
exclusions:
Day (Date) | PRN | Centres
-----------+-------+--------
2 (Feb 08) | 04 | NGS
3 (Feb 09) | 03 | SIO
3 (Feb 09) | 22 | NGS,SIO
6 (Feb 12) | 03 | NGS,SIO
6 (Feb 12) | 25 | NGS
7. Sparse tracking data for PRN03 on day 6 (Feb 12) caused the disagreement
between the weighted average and CODE solutions. As indicated by the long
arc process results, CODE solution may, in this case, be close to the truth
during intervals without data.
ORBIT COMBINATION AND EVALUATION STATISTICS:
For a complete description of tables and statistics, please refer to the report
posted on CDDIS (IGS07357.SUM).
Table 1: Week 0735 summary. (Feb 06, 1994 - Feb 12, 1994)
Table 1.0735.a GPS week: 0735 MJD: 49389.0-49395.0
Mean and standard deviations of transformation parameters.
WRMS - orbit RMS weighted by the SP3 header accuracy codes.
Units: meters, mas, ppb, nano-sec, nano-sec/day.
CENT| DX DY DZ RX RY RZ SCL RMS WRMS | TOFT TDRFT RMS
----|---------------------------------------------------|---------------------
cod | .00 .02 .02 .56 -.26 .28 .1 .12 .12 | 2.8 2.1 1232.8
| .01 .01 .01 .18 .36 .30 .1 | 1.5 2.3
emr | .02 .00 .00 .77 .19 .27 -.4 .18 .18 | 265.4 193.8 59.9
| .01 .01 .02 .40 .37 .09 .1 | 204.6 72.5
esa | .01 .01 .00 .61 .07 -.47 .1 .21 .20 | -14.5 -6.4 24.3
| .00 .00 .01 .49 .49 .30 .2 | 19.7 37.7
gfz | -.04 .01 .01 .13 1.25 -.44 -.4 .14 .13 | -269.9 -28.2 12.3
| .01 .01 .01 .12 .19 .13 .1 | 37.0 4.5
jpl | .00 -.02 .02 .62 .12 .11 -.1 .12 .12 | -276.3 -20.6 13.8
| .01 .01 .01 .22 .28 .25 .1 | 36.0 5.0
ngs | .03 .01 -.05 .87 -.05 .61 1.7 29.40 16.17 | .0 .0 .0
| .02 .05 .02 .72 .50 .47 .5 | .0 .0
sio | .01 -.02 -.06 1.08 .29 -.10 .6 29.41 29.41 | .0 .0 .0
| .01 .01 .01 .18 .35 .32 .3 | .0 .0
Table 1.0735.b GPS week : 0735 MJD: 49389.0-49395.0
Satellite position sigmas for the combined orbits
(coded in the IGS SP3 orbit files).
"E" flags eclipsing satellites.
Units: cm.
Day of GPS week
PRN | 0 1 2 3 4 5 6 | Remarks
------|-----------------------------|------------------------------------------
1 | 6 6 7 6 5 7 6 |
2E | 7 6 7 7 6 8 7 |
3 | 4 4 5 6 11 4 24 | Sparse tracking on days 4 and 6.
4 | 8 8 6 7 5 7 6 |
5E | 7 7 7 6 7 6 6 |
7 | 6 9 4 6 6 5 6 |
9 | 5 6 6 5 4 6 5 |
12 | 5 6 4 4 3 5 5 |
13 | 5 6 6 5 5 7 4 |
14E | 6 6 8 7 8 7 5 |
15 | 6 9 9 6 6 7 6 |
16E | 6 10 7 11 6 7 7 |
17 | 5 5 5 5 5 4 6 |
18 | 5 4 6 6 5 5 5 |
19 | 4 4 5 5 6 5 5 |
20E | 8 7 9 5 5 6 7 |
21E | 6 8 7 6 6 6 5 |
22E | 7 8 6 0 19 8 8 | Maneuvre on day 3.
23E | 7 8 7 6 6 7 9 |
24 | 6 7 10 7 7 6 6 |
25 | 6 8 10 6 9 7 15 |
26 | 5 6 4 5 5 8 6 |
27 | 4 4 6 5 5 4 4 |
28 | 5 7 6 5 7 7 8 |
29 | 5 5 5 7 5 5 5 |
31 | 6 6 6 5 5 5 8 |
For Table 2 and Table 3 statistics, please refer to the report posted on
CDDIS (IGS07357.SUM).
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