Subject: [IGSREPORT-0912] IGS Final Orbit Comb(737)
From: Analysis Centres Coordinator / Geodetic Survey of Canada
Date: Wed, 20 Apr 1994 11:50:28 PDT

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IGS Electronic Report    Wed Apr 20 11:50:28 PDT 1994      Message Number 0912
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Author: Analysis Centres Coordinator / Geodetic Survey of Canada
Subject: IGS Final Orbit Comb(737)

IGS Final Orbit Combination Week 0737             (Feb 20, 1994 - Feb 26, 1994)

Contacts: F. Lahaye ([email-masked]), J. Kouba ([email-masked])

COMBINATION STRATEGY:

For a complete description of combination strategy, please refer to the report
posted on CDDIS (IGS07377.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:

 IGS07370-6.SP3  IGS GPS ephemeris files for days 0-6, week 0737 in SP3 format.
 IGS07377.ERP    Earth rotation parameters (ERP) associated with ephemerides.
 IGS07377.SUM    Complete report.

The old Rapid Service files have been renamed to:

 IGR07370-6.SP3  Rapid Service ephemeris files for days 0-6.
 IGR07377.ERP    Rapid Service earth rotation parameters (ERP).
 IGR07377.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 0 (Feb 20) and 4 (Feb 24) are
   due to clock shifts for PRN21 and PRN03 respectively 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
           -----------+--------------+---------+---------------
           2 (Feb 22) | All          | JPL     | Few 100ns.
           5 (Feb 25) | All          | JPL     | Few us.
           5 (Feb 25) | 14,15,18,22, | ESA     | Few 100ns.
                      | 25,28,31     |         |
           6 (Feb 26) | All          | EMR     | Noise ~100ns.

4. Note the anomalous rotations in X and Z for SIO on days 2-6 (Feb 22-26).
   The SIO solutions for those days were not included in the orbit combination.

5. Several 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  
               -----------+----------+--------
               0 (Feb 20) | 22       | NGS
               2 (Feb 22) | 14       | NGS
               3 (Feb 23) | 20,22,25 | NGS
               5 (Feb 25) | 1,22,25  | NGS
               6 (Feb 26) | 28       | NGS,SIO

ORBIT COMBINATION AND EVALUATION STATISTICS:

For a complete description of tables and statistics, please refer to the report
posted on CDDIS (IGS07377.SUM).

Table 1: Week 0737 summary.                       (Feb 20, 1994 - Feb 26, 1994)

Table 1.0737.a   GPS week: 0737   MJD: 49403.0-49409.0

         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 | -.01  .01  .00   .30   .06   .48   .1   .15   .14 |    2.4    3.7 1027.7
    |  .01  .01  .01   .40   .57   .29   .2             |    1.4    3.0
emr |  .02  .01 -.01   .22   .10   .20   .0   .20   .20 |  222.1  121.3   10.1
    |  .02  .01  .01   .40   .52   .30   .2             |  206.6  109.7
esa |  .00  .02  .01   .67  -.32  -.97   .2   .19   .18 |  -14.3   -1.6   34.2
    |  .01  .01  .02   .32   .36   .22   .2             |   21.4    9.9
gfz | -.03  .02  .00   .30  1.61  -.56  -.4   .18   .14 |-241600  -18.4   11.6
    |  .01  .00  .02   .19   .22   .20   .1             |98788.2   15.3
jpl |  .01 -.03  .01   .61   .33   .41   .0   .12   .12 | -854.1  517.8 1512.7
    |  .01  .01  .01   .42   .38   .19   .1             | 1635.5 1278.0
ngs |  .01 -.02  .00   .27  -.45   .42   .9  1.96   .66 |     .0     .0     .0
    |  .08  .04  .04  1.77   .92  1.21   .8             |     .0     .0
sio |  .02 -.02 -.08 -3.34 -1.96   .19  1.0   .26   .26 |     .0     .0     .0
    |  .02  .02  .01  4.10   .81   .49   .2             |     .0     .0

Table 1.0737.b   GPS week : 0737   MJD: 49403.0-49409.0

         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  |   8   8  10  11   6   9   8 |
   2  |   5   6   9   6   6   8   8 |
   3  |   6   4   4   6   4   9   8 |
   4  |  10   7   7   7   6   9  11 |
   5  |   8   6   6  10   5   6   7 |
   7  |   6   5   7   7   7   7  12 |
   9  |  10   8   8   6  11   6   9 |
  12  |   6   5   6   6   6   5   8 |
  13  |   6   5   5   6   6   5   7 |
  14E |   8   8   7  12   8  10  11 |
  15  |   8   8   7   8  11   9   9 |
  16E |  10   9  10   8   7  12  12 |
  17  |   6   5   5   6   5   8   8 |
  18  |   6   5   5   7   6   7  11 |
  19  |   5   5   5   5   6   6   8 |
  20  |   6  11   5   7   5   8   6 |
  21E |  10   9   8   9   8   7   8 |
  22  |   9   7  10   7  12  11  13 |
  23E |  13  12  14  12   9   8   8 |
  24  |  10   6  10   6   7   8   7 |
  25  |   7   9   9   8   9   9   9 |
  26  |   7   9   8   6   6   9  10 |
  27  |   8   7   9   8   5   6   8 |
  28  |   8   9   9   8   8   7  15 |
  29  |   5   6   6   6   6   5   7 |
  31  |   8  10   6   8   7   8  10 |

For Table 2 and Table 3 statistics, please refer to the report posted on
CDDIS (IGS07377.SUM).