Subject: [IGSREPORT-0836] IGS Final Orbit Comb(733)
From: Analysis Centres Coordinator / Geodetic Survey of Canada
Date: Thu, 10 Mar 1994 11:55:11 PST

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IGS Electronic Report    Thu Mar 10 11:55:11 PST 1994      Message Number 0836
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Author: Analysis Centres Coordinator / Geodetic Survey of Canada
Subject: IGS Final Orbit Comb(733)

IGS Final Orbit Combination Week 0733             (Jan 23, 1994 - Jan 29, 1994)

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

COMBINATION STRATEGY:

For a complete description of the combination strategy, see IGSMAIL #832.

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:

 IGS07330-6.SP3  IGS GPS ephemeris files for days 0-6, week 0733 in SP3 format.
 IGS07337.ERP    Earth rotation parameters (ERP) associated with ephemerides.
 IGS07337.SUM    Complete report.

The old Rapid Service files have been renamed to:

 IGR07330-6.SP3  Rapid Service ephemeris files for days 0-6.
 IGR07337.ERP    Rapid Service earth rotation parameters (ERP).
 IGR07337.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. EMR satellite clock corrections were excluded from combination on days 2 and
   4 (Jan 25 and 27) due to unusually large RMS (~ 100 nanosec.).

3. COD satellite clock corrections (broadcast) exhibit breaks on day 2
   (Jan 25). Since COD values are used for alignment to broadcast clocks and 
   since ESA clocks are the closest to GPS time, all centres were initially 
   aligned to ESA on day 2 (Jan 25).

4. Exceptionaly and contrary to our usual practice of including all satellite
   orbital data submitted, PRN 24 was excluded from combination from day 2 and
   on (Jan 25-29). This is due to the inexistent or sparse tracking data
   internationaly obtained from this satellite during those days.
   Since the amount of data collected from PRN 24 during this time span is    
   very small, we assume this will not inconvenience IGS orbit users.

5. The anomalous NGS solution for PRN03 on day 0 (Jan 23) was not included in
   combination but used in statistics computation (see Table 2.0733.0 and
   Table 3.0733.0) and long-arc orbit evaluation.

6. Satellite state vector resets were modeled for PRN02 and PRN05 on day 3
   (Jan 26) in the long-arc analysis.

ORBIT COMBINATION AND EVALUATION STATISTICS:

For a complete description of tables and statistics, see IGSMAIL #832.

Table 1: Week 0733 summary.                       (Jan 23, 1994 - Jan 29, 1994)

Table 1.0733.a   GPS week: 0733   MJD: 49375.0-49381.0

         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  .00  .01  1.33  -.05   .16   .0   .13   .12 |   -5.2    4.3   74.4
    |  .01  .01  .01   .35   .07   .09   .2             |    6.3    9.9
emr |  .00  .00  .00  2.02   .89   .04  -.1   .10   .10 |  -86.0  -22.3   60.4
    |  .01  .00  .01   .55   .23   .20   .1             |  108.4   38.7
esa |  .01  .00  .02  1.58  -.12  -.60   .1   .19   .17 |     .7     .4    2.3
    |  .01  .01  .01   .28   .35   .53   .2             |   10.4   11.1
gfz | -.02  .00  .01  1.20  1.89  -.28  -.6   .17   .12 |  -61.4  -16.7     .7
    |  .01  .01  .00   .21   .23   .22   .1             |   40.1   10.2
jpl | -.01  .04 -.01  1.22   .38  -.01   .2   .13   .13 |  -61.7  -17.2     .8
    |  .01  .01  .01   .44   .17   .12   .1             |   40.6   10.6
ngs |  .03 -.05 -.02   .56  -.84   .58  1.7   .77   .37 |     .0     .0     .0
    |  .01  .01  .03   .42   .45   .19   .3             |     .0     .0
sio |  .02 -.04 -.03  1.91   .64   .13   .4   .19   .20 |     .0     .0     .0
    |  .01  .01  .01   .19   .33   .08   .1             |     .0     .0

Table 1.0733.b   GPS week : 0733   MJD: 49375.0-49381.0

         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  |   5   4   5   5   5   4   5 |
   2E |   8   6   9   8   6   7   8 |
   3  |   9   4   4   5   4   4   4 |
   4  |   6   8   6   7   5   6   6 |
   5E |   7   7   7   7   9   6   6 |
   7  |   5   5   5   5   4   3   4 |
   9  |   4   5   4   5   5   8   4 |
  12  |   4   4   4   5   5   6   4 |
  13  |   6   7   5   6   5   4   3 |
  14  |   4   5   4   4   4   5   5 |
  15  |   6   5   6   5   5   5   6 |
  16  |   7   5   5   5   8   7   6 |
  17  |   5   5   4   4   4   4   4 |
  18  |   4   4   5   4   5   4   5 |
  19  |   3   4   4   3   4   3   3 |
  20E |   7   7   8   9   7  24  10 |
  21  |   5   6   5   5   5   5   4 |
  22E |   5   7   7   9  16   6   9 |
  23  |   6   8   7   5   5   6   5 |
  24  |   8  11 --- --- --- --- --- | Sparse or no tracking data on days 2-6.
  25  |   5   6   5   7   7   7   5 |
  26  |   6   6   6   6   5   5   6 |
  27  |   4   4   3   4   4   4   4 |
  28  |   4   4   4   5   5   4   4 |
  29  |   4   3   3   4   3   4   4 |
  31  |   4   5   5   5   5   5   5 |

For tables 2 and 3, please refer to the complete report (IGS07337.SUM) posted
on CDDIS.