Subject: [IGSMAIL-5518]: GPS week 1400 model changes made at CODE
From: Stefan Schaer <[email-masked]>
To: igsmail <[email-masked]>
Date: Fri, 22 Dec 2006 15:52:02 +0100

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IGS Electronic Mail      22 Dec 06:52:16 PST 2006      Message Number 5518
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Author: Stefan Schaer, Urs Hugentobler

Dear IGS colleagues,

A remarkable number of model changes/improvements was activated in
CODE's IGS analysis starting with GPS week 1400. Note that changes that
must be considered as mandatory for IGS analysis are indicated in our
listing with "+":

* Absolute GNSS PCV model (APCV):
   + Switch to the absolute GNSS PCV model IGS05_1400 (latest version:
     IGS05_1402). For details see: IGS Mails 5272, 5318, 5438.
   + Consideration of receiver antenna radome codes (actually done since
     week 1367) became relevant with the use of the absolute PCV model.
   - For ionosphere analysis, this model change has an effect on L1-L2
     receiver PCV, but not on satellite PCV correction (L1-L2=0).

* Terrestrial reference frame (TRF):
   + Use of IGS05 TRF realization. Note: IGS05 and ITRF2005 velocity
     vectors are identical. IGS05 is conform to the absolute PCV model,
     ITRF2005 to relative PCV. For details see: IGS Mails 5447, 5455.
   - List of IGS05 fiducial stations was completed with (12) antenna
     sharing stations:
       -----------------------------------
       IGS05           Added      Category
       -----------------------------------
       DARW 50134M001  DARR       IGLOS
       DAV1 66010M001  DAVR       IGLOS
       GODE 40451M123  GODZ       IGLOS
       GOLD 40405S031  GOL2       IGS
       IRKT 12313M001  IRKM       IGS
       MADR 13407S012  MAD2       IGS
       ONSA 10402M004  OS0G       IGLOS
       BAHR 24901M002  S051       NGA
       THU3 43001M002  THU2       IGLOS
       TIDB 50103M108  TID1/TID2  IGS
       YAR1 50107M004  YAR2       IGS
       -----------------------------------
     Note: An interesting detail is the fact that YAR1 (inactive), not
     YAR2 (active) is declared as IGS05 reference station.

* Changes concerning CODE weekly analysis reports:
   - Verification of geodetic datum definition: Residuals wrt IGS05 are
     provided for the (extended) list of IGS05 fiducial stations in our
     weekly analysis summary files. See:
       http://igscb.jpl.nasa.gov/mail/igsreport/2006/msg01133.html
       http://igscb.jpl.nasa.gov/mail/igsreport/2006/msg01150.html
       http://igscb.jpl.nasa.gov/mail/igsreport/2006/msg01168.html
       http://igscb.jpl.nasa.gov/mail/igsreport/2006/msg01184.html
       http://igscb.jpl.nasa.gov/mail/igsreport/2006/msg01210.html
       http://igscb.jpl.nasa.gov/mail/igsreport/2006/msg01234.html
     "R" indicates fiducial stations rejected from datum definition,
     like, e.g., MKEA (due to recent earthquake).
   - The 7 parameters of the corresponding Helmert transformation are
     listed. These transformation parameters should be consistent to
     those provided, e.g. for week 1400, in:
       http://igscb.jpl.nasa.gov/mail/igsreport/2006/msg01137.html
       http://igscb.jpl.nasa.gov/mail/igsreport/2006/msg01139.html
   - In addition, retrievals of weekly geocenter coordinates are given
     (in the TRF used).

* SINEX:
   + GNSS antenna offset parameters (constrained to IGS05 PCV model
     values) are included in SINEX for both the GPS and the GLONASS
     satellite constellation.
   - We do no longer provide CoM weekly station coordinates (translation
     defined by geocenter, geocenter coordinates assumed to 0/0/0) but
     started to submit SINEX containing CoN coordinates (conform to the
     used TRF not only in terms of rotation but also in terms of
     translation).
   - Geocenter coordinates (constrained to 0/0/0) are included.

* Troposphere modeling:
   - Mapping function: changed from Niell to GMF (Global MF).
   - A priori model for hydrostatic component: changed from a
     Saastamoinen-based to GPT (Global Pressure Temperature) model.
     Note: GMF/GPT models were developed by Johannes Boehm, TU Vienna.
   - Gradient model: refined.
     Note: Elevation mask angle of 3 degrees remains unchanged.

* Solar radiation pressure (RPR) a priori model:
   - Start to use CODE RPR model coefficients for GLONASS.
   - Use updated model coefficients for GPS. This update is relevant in
     particular for all Block II-R satellites.
   - Special RPR handling of R18 (behaving differently compared to other
     GLONASS satellites) turned out to be erroneous and was switched back
     to the zero model (starting with week 1406). This RPR modeling
     problem will be further investigated.

* Ocean tide loading (OTL):
   + CMC (center of mass) correction applied in GNSS POD process,
     based on the FES2004 OTL model (already used since week 1367).
   + hardisp.f (developed by Duncan Agnew, UCSD) implemented to consider
     displacements from a total of 141 constituent tides (see also
     IGS Mail 5300).

* Application of Shapiro effect for GNSS:
   + Shapiro (relativistic signal propagtion delay) effect is taken into
     account to be in accordance with the absolute GNSS PCV model.

* Mean pole:
   - Mean pole computed according to IERS2003 standards.

* Phase windup:
   - Not only the geometrical part of the polarization effect is
     considered but the effect due to the nominal attitude motion of the
     GNSS satellites is taken into account. Note that this model change
     does just affect our clock results.

* Format changes:
   + SINEX: Inclusion of satellite antenna offset parameters (see above).
   + SP3: Added 4th header comment line according to IGS standard:
============================================================
/* PCV:IGS05_1400 OL/AL:FES2004  NONE     YN ORB:CoN CLK:CoN
============================================================
     Legend:
       PCV model used
       Ocean/atmospheric tidal loading (OL/AL) model used
       CMC applied (for OL and for AL, respectively)
       Reference frame definition concerning orbits included
       Reference frame definition concerning clocks included
   + CLK: Clock RINEX with additional header records to specify
       PCV model used and
       DCB (differential code bias) model used (see also IGS Mail 5490):
================================================================================
G GPSEST V5.1       IGS05_1400                              SYS / PCVS 
APPLIED
G GPSEST V5.1       P1C1.DCB @ ftp.unibe.ch/aiub/CODE/      SYS / DCBS 
APPLIED
================================================================================
     Note: We did not change the clock RINEX format version number (2.00)
     because not all mandatory records of format 3.00 can be included.

Best regards,

The CODE AC Team