Subject: [IGSREPORT-0909] IGS Final Orbit Comb(734)
From: Analysis Centres Coordinator / Geodetic Survey of Canada
Date: Wed, 20 Apr 1994 11:39:13 PDT

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IGS Electronic Report    Wed Apr 20 11:39:13 PDT 1994      Message Number 0909
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Author: Analysis Centres Coordinator / Geodetic Survey of Canada
Subject: IGS Final Orbit Comb(734)

IGS Final Orbit Combination Week 0734             (Jan 30, 1994 - Feb 05, 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 (IGS0734.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:

 IGS07340-6.SP3  IGS GPS ephemeris files for days 0-6, week 0734 in SP3 format.
 IGS07347.ERP    Earth rotation parameters (ERP) associated with ephemerides.
 IGS07347.SUM    Complete report.

The old Rapid Service files have been renamed to:

 IGR07340-6.SP3  Rapid Service ephemeris files for days 0-6.
 IGR07347.ERP    Rapid Service earth rotation parameters (ERP).
 IGR07347.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. Starting with week 0734 the USNO Bulletin B pole used as reference is first
   corrected with the parameters published in the IERS 1992 Annual Report,
   page II-17 (Table II-3), which align the pole series with the ITRF
   (see COMBINATION STRATEGY above).

3. There was a maneuvre of PRN16 on day 3 (Feb 2) (ref. NANU 032-94033). 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 PRN16 on the day of maneuvre were excluded from combination based on the
   assumption that they are extrapolation instead of actual modeling.

4. Data from PRN16 on day 3 was excluded from long arc analysis and a state
   vector reset was modeled on the following day for that satellite for all
   centres and the combined orbit.

5. 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 01) |  All    | JPL     | Few us.
           3 (Feb 02) |  All    | JPL     | Few us.
           5 (Feb 04) |  All    | EMR     | Noise ~100 ns.

7. 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 (Jan 30) |  24   | NGS
               3 (Feb 02) |  16   | NGS, SIO
               4 (Feb 03) |  16   | JPL
               6 (Feb 05) |  04   | NGS

8. Permanent implementation of AS occured on day 1 (Jan 30).

ORBIT COMBINATION AND EVALUATION STATISTICS:

For a complete description of tables and statistics, please refer to the report
posted on CDDIS (IGS0734.SUM).

Table 1: Week 0734 summary.                       (Jan 30, 1994 - Feb 05, 1994)

Table 1.0734.a   GPS week: 0734   MJD: 49382.0-49388.0

         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  .01  .03  1.03   .13   .41   .1   .15   .15 |    4.6    -.7   75.0
    |  .01  .01  .01   .48   .31   .13   .2             |    4.5    9.5
emr |  .03  .00 -.02  1.30   .79   .42  -.1   .23   .23 | -208.8   62.4   42.8
    |  .03  .02  .02   .31   .30   .49   .2             |   54.1   53.1
esa |  .01  .02  .00   .95  -.14  -.44   .0   .21   .19 |   -3.1  -19.6   15.4
    |  .00  .01  .01   .37   .31   .48   .2             |    6.4    7.2
gfz | -.02  .01  .00   .78  1.83  -.41  -.4   .14   .13 | -149.2   -4.4   15.4
    |  .01  .01  .01   .52   .32   .15   .1             |   35.7   59.3
jpl | -.01 -.02  .02  1.21   .55   .17  -.1   .65   .66 |  768.7 -993.615503.9
    |  .01  .03  .01   .60   .41   .22   .1             | 1836.7 3514.3
ngs |  .02 -.02 -.01   .74  -.42   .62  1.6706.27124.15 |     .0     .0     .0
    |  .02  .04  .05   .48   .49   .92   .6             |     .0     .0
sio |  .02 -.04 -.08  1.44   .43  -.23   .6706.68706.68 |     .0     .0     .0
    |  .01  .02  .02   .77   .36   .25   .2             |     .0     .0

Table 1.0734.b   GPS week : 0734   MJD: 49382.0-49388.0

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

For Table 2 and Table 3 statistics, please refer to the report posted on
CDDIS (IGS0734.SUM).