Subject: [IGSMAIL-0703] Wk 751-754 Final IGS orbits
From: AC Coordinator
Date: Mon, 8 Aug 1994 9:43:30 PDT

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IGS Electronic Mail      Mon Aug  8  9:43:30 PDT 1994      Message Number 0703
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Author: AC Coordinator
Subject: Wk 751-754 Final IGS orbits

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IGS Final orbits/clocks completed and put onto CDDIS (Weeks 751 - 754)
                                                     ( May 29 - June 25, 1994)
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According to the recommendations of the Analysis Centre Workshop the IGS
Rapid Orbits were recomputed using up to date orbits and the final EOP values
of Bulletin B, published by IERS. ( Daily values, page 2 of Bull. B were
used). The EOP were corrected for the difference between the IERS pole series 
and ITRF as published in the IERS 1992 Annual Report (p. II-17, Table II-3),
so both the IGS orbits and associated ERP files are consistent with ITRF92
(current epoch).

We have downloaded all submitted ephemeris and ERP files from CDDIS before
the final orbit/clock combination to ensure that the sets are complete and up
to date. In the final combination we have largely followed the actions taken
during the Rapid orbit generation and since there were very few orbit
resubmissions, both the IGS Rapid  and Final orbits are virtually same except
for the the orientation difference (the current Bull.A and final Bull.B).
Orbit evaluation are also nearly the same, since we used centre specific ERP
in these long arc evaluations. For more information see the corresponding
summary files on CDDIS.

Starting with the GPS week 742 a new clock combination scheme was put in
place for the final orbit/clock combinations. The clock solution alignment
and centre clock weight assignment are based on non SA broadcast  satellite
corrections only (PRN12, 15, 20). This should result in more realistic and
objective clock weighting than employed before, provided that the non SA
satellites are representatives of each centre clock solution quality.

PRODUCTS GENERATED:

The resulting final IGS ephemeris and clocks are in daily files in the SP3
format. The sat. orb. accuracy codes displayed in the headers are based on
weighted RMS for each satellite. Note that each file contains all the submitted
satellites. If satellite or centre had to be excluded from the combination it
is noted in the summary file along with the reason for doing so.

The IGS FINAL ORBIT files generated and uploaded into CDDIS @ NASA/GSFC are:

IGS07510-6.SP3   IGS GPS orbit/clock files for days 0-6, week 0751
IGS07520-6.SP3   IGS GPS orbit/clock files for days 0-6, week 0752
IGS07530-6.SP3   IGS GPS orbit/clock files for days 0-6, week 0753
IGS07540-6.SP3   IGS GPS orbit/clock files for days 0-6, week 0754

IGS07517.ERP    EOP associated with the above orbits (Bull. B aligned to ITRF)
IGS07527.ERP    EOP associated with the above orbits (Bull. B aligned to ITRF)
IGS07537.ERP    EOP associated with the above orbits (Bull. B aligned to ITRF)
IGS07547.ERP    EOP associated with the above orbits (Bull. B aligned to ITRF)

IGS07517.SUM    Complete summary/statistics report
IGS07527.SUM    Complete summary/statistics report
IGS07537.SUM    Complete summary/statistics report
IGS07547.SUM    Complete summary/statistics report

The old Rapid Orbit files have been renamed (on CDDIS) to:
(Note this is temporary, based on discussions with AC and GB and may be
changed )

IGR07510-6.SP3   Rapid service orbits/clocks for days 0-6, week 751
IGR07520-6.SP3   Rapid service orbits/clocks for days 0-6, week 752
IGR07530-6.SP3   Rapid service orbits/clocks for days 0-6, week 753
IGR07540-6.SP3   Rapid service orbits/clocks for days 0-6, week 754

IGR07517.ERP     Rapid service EOP associated with the above orbits (Bull A)
IGR07527.ERP     Rapid service EOP associated with the above orbits (Bull A)
IGR07537.ERP     Rapid service EOP associated with the above orbits (Bull A)
IGR07547.ERP     Rapid service EOP associated with the above orbits (Bull A)

IGR07517.SUM     Rapid service complete summary/statistic report 
IGR07527.SUM     Rapid service complete summary/statistic report 
IGR07537.SUM     Rapid service complete summary/statistic report 
IGR07547.SUM     Rapid service complete summary/statistic report 

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REMARKS/CORRECTIONS:

None

[Mailed From: Jan Kouba <[email-masked]>]