Subject: [IGSREPORT-0911] IGS Final Orbit Comb(736)
From: Analysis Centres Coordinator / Geodetic Survey of Canada
Date: Wed, 20 Apr 1994 11:47:40 PDT

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IGS Electronic Report    Wed Apr 20 11:47:40 PDT 1994      Message Number 0911
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Author: Analysis Centres Coordinator / Geodetic Survey of Canada
Subject: IGS Final Orbit Comb(736)

IGS Final Orbit Combination Week 0736             (Feb 13, 1994 - Feb 19, 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 (IGS07367.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:

 IGS07360-6.SP3  IGS GPS ephemeris files for days 0-6, week 0736 in SP3 format.
 IGS07367.ERP    Earth rotation parameters (ERP) associated with ephemerides.
 IGS07367.SUM    Complete report.

The old Rapid Service files have been renamed to:

 IGR07360-6.SP3  Rapid Service ephemeris files for days 0-6.
 IGR07367.ERP    Rapid Service earth rotation parameters (ERP).
 IGR07367.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, 3, 5 and 6 (Feb 13, 16, 18
   and 19) are due to a delay in acknowledging clock resets of several micro-
   seconds on PRN 03 by broadcast message. Consequently, PRN03 broadcast clock
   corrections were not used in the estimation of the initial GPS time
   alignment parameters.

3. 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 13) |  03   | EMR,NGS
               3 (Feb 16) |  03   | NGS,SIO
               4 (Feb 17) |  03   | NGS

ORBIT COMBINATION AND EVALUATION STATISTICS:

For a complete description of tables and statistics, please refer to the report
posted on CDDIS (IGS07367.SUM).

Table 1: Week 0736 summary.                       (Feb 13, 1994 - Feb 19, 1994)

Table 1.0736.a   GPS week: 0736   MJD: 49396.0-49402.0

         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   .66   .55   .24   .1   .14   .13 |    3.4    3.4  600.4
    |  .01  .00  .01   .26   .33   .21   .2             |    1.1    2.5
emr |  .01  .01 -.01   .74   .60   .10  -.1   .58   .16 |  258.8   51.8   10.7
    |  .01  .01  .01   .40   .39   .28   .1             |  232.5   89.2
esa |  .00  .00  .00   .68   .16  -.72   .1   .23   .22 |  -24.3   -5.9   13.2
    |  .01  .01  .01   .38   .72   .47   .1             |   16.1    7.9
gfz | -.03  .01  .01   .08  1.81  -.45  -.4   .15   .12 |  -64.2  -24.2    8.1
    |  .01  .01  .01   .13   .38   .17   .2             |  474.8   12.3
jpl |  .01 -.03  .02   .86   .70   .39   .0   .12   .12 |  -68.5  -16.0   14.4
    |  .01  .00  .01   .19   .42   .19   .1             |  475.4   10.0
ngs |  .02 -.02  .00   .90   .54   .50   .9  6.62   .38 |     .0     .0     .0
    |  .02  .02  .03   .29   .51   .74   .7             |     .0     .0
sio |  .03 -.03 -.08  1.38  1.60  -.12   .7   .50   .50 |     .0     .0     .0
    |  .02  .01  .02   .30   .37   .32   .2             |     .0     .0

Table 1.0736.b   GPS week : 0736   MJD: 49396.0-49402.0

         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   5   7   5   5   6   7 |
   2E |   5   5   7   7   7   7   5 |
   3  |  21   4   6  28  14   5  10 | Sparse tracking on day 0 and 3.
   4  |   6   6   7   6   6   8   8 |
   5E |   5   6   7   6   4   6   7 |
   7  |   6   4   5   5   5   5   6 |
   9  |   5   5   6   5   5   5   7 |
  12  |   4   5   6   6   5   7   7 |
  13  |   5   7   6   6   5   6  13 |
  14E |   5   5   8   6   5   8  10 |
  15  |   5   6   6   6   7   6   6 |
  16E |   8   9   9   8   9   9  19 |
  17  |   4   4   6   5   5   5   6 |
  18  |   4   5   6   7   5   4   5 |
  19  |   4   4   4   4   4   4   5 |
  20E |   7   7   8   6   5   6   7 |
  21E |   6   6   6  10   9   9   9 |
  22E |   8   7  13   6  10   9   8 |
  23E |   7  10  10  10  12  12  11 |
  24  |   6   5  11   6   7   8   9 |
  25  |   7   5  11  10   7   7   7 |
  26  |   6   5   5   5   5   5   8 |
  27  |   4   5   5   5   5   5   4 |
  28  |   6   6   7   7   8   6   5 |
  29  |   4   5   5   6   5   6   4 |
  31  |   7   6   6   5   5   7   6 |

For Table 2 and Table 3 statistics, please refer to the report posted on
CDDIS (IGS07367.SUM).