[IGSREPORT-0834] IGS Final Orbit Comb(731)

[Analysis]

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IGS Electronic Report    Thu Mar 10 11:50:09 PST 1994      Message Number 0834
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Author: Analysis Centres Coordinator / Geodetic Survey of Canada
Subject: IGS Final Orbit Comb(731)

IGS Final Orbit Combination Week 0731             (Jan 09, 1994 - Jan 15, 1994)

Contacts: F. Lahaye (lahaye at geod.emr.ca), J. Kouba (kouba at geod.emr.ca)


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:

 IGS07310-6.SP3  IGS GPS ephemeris files for days 0-6, week 0731 in SP3 format.
 IGS07317.ERP    Earth rotation parameters (ERP) associated with ephemerides.
 IGS07317.SUM    Complete report.

The old Rapid Service files have been renamed to:

 IGR07310-6.SP3  Rapid Service ephemeris files for days 0-6.
 IGR07317.ERP    Rapid Service earth rotation parameters (ERP).
 IGR07317.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. ESA satellite clock corrections were not incuded in the combination since
   they exhibit systematic effects at the 10 nano-seconds level due to not
   accounting for relativistic effects.
  
3. On day 3 (Jan 12), JPL and GFZ clock are excluded from combination due to a
   clock reset at ALGO. The EMR solution, properly aligned, is provided here.

4. A satellite state vector reset was modeled for PRN05 on day 3 (Jan 12) at
   0h00 UTC in the long arc process.


ORBIT COMBINATION AND EVALUATION STATISTICS:

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


Table 1: Week 0731 summary.                       (Jan 09, 1994 - Jan 15, 1994)

Table 1.0731.a   GPS week: 0731   MJD: 49361.0-49367.0

         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  .02  1.18   .05   .18   .0   .12   .10 |     .5     .0   74.7
    |  .01  .01  .01   .28   .45   .09   .0             |    1.9    1.0
emr |  .00  .00  .00  1.95   .27   .11  -.1   .18   .14 | -524.1  -38.2     .7
    |  .01  .01  .01   .50   .55   .32   .2             |   68.7    6.6
esa |  .01  .01  .00  1.64   .03  -.44   .0   .24   .18 |     .1   -8.3   12.0
    |  .01  .01  .01   .45   .49   .55   .3             |   12.4   16.7
gfz | -.04  .00  .01  1.25  1.52  -.29  -.4   .12   .12 |  -87.8  -26.5   71.2
    |  .01  .01  .01   .30   .48   .22   .1             |  173.6   24.1
jpl |  .01  .04 -.01  1.22   .28   .09   .1   .16   .18 |  -91.5  -18.8   71.1
    |  .01  .00  .01   .39   .31   .16   .2             |  178.2    5.9
ngs |  .00 -.04 -.02   .73  -.61   .45  1.7   .36   .33 |     .0     .0     .0
    |  .03  .02  .03   .52  1.20   .41   .3             |     .0     .0
sio |  .02 -.04 -.05  2.66   .37   .04   .4   .28   .29 |     .0     .0     .0
    |  .02  .02  .01   .39   .34   .38   .3             |     .0     .0

Table 1.0731.b   GPS week : 0731   MJD: 49361.0-49367.0

         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  |   7   5   5   7   5   6   7 |
   2E |   7   7   6   6   6   6   6 |
   3  |   5   4   4   5   4   5   4 |
   4E |   9   6   8   9  25   6   6 |
   5E |  24  16   7  46   7   8  17 |
   7  |   5   4   5   5   4   5   4 |
   9  |   6   6   5   9   6   6   5 |
  12  |   6   6   5   9   4   4   5 |
  13  |   7   6   5   6   6   6   5 |
  14  |   4   4   5   5   4   6   5 |
  15E |   5   4   5   7   6   7   6 |
  16  |   5   5   6   9   5   6   5 |
  17E |   6   7   6   6   5   5   5 |
  18  |   3   3   4   6   4   4   4 |
  19  |   5   4   4   4   4   4   3 |
  20E |   7   7   8  11   8   6   8 |
  21  |   5   3   6   5   6   5   4 |
  22E |   5   8   6   6   6   6   6 |
  23  |   6   7   8   6   7   7   6 |
  24E |   9   9   6  10   6   7   6 |
  25  |   7   5   6   8   6   6   5 |
  26  |   6   6   6   6   7   5   7 |
  27  |   5   4   4   4   4   4   4 |
  28  |   4   4   4   4   5   4   4 |
  29  |   3   4   5   3   4   5   4 |
  31  |   6   5   4   7   6   5   5 |

For tables 2 and 3, please refer to the complete report (IGS07317.SUM) posted
on CDDIS.