[IGSREPORT-27564] Wk 2122 MIT T2 RNAAC Analyis Report

[Tom Herring]

Author: Thomas Herring

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MIT R/GNAAC  ANALYSIS REPORT GPS-WEEK 2122    Dates: 20sep06  to  20sep12 
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MIT (Massachusetts Institute of Technology) 
Room 54-332
77 Massachusetts Avenue, 
Cambridge,  MA  02139
e-mail: tah at mit.edu 
tel:    (617)253-5941 (Tom Herring)
fax:    (617)253-6385

PRODUCTS GENERATED:
The following products are generated and uploaded into CDDIS @ NASA/GSFC
   MIT2122p.SNX   RNAAC combination sinex file from all available analysis centers
                  with the GNAAC sinex files.
   MIT2122p.SUM   Name of this summary file

0.0 Starting Week 1934, Switched to IGS14 realization of the reference frame.

0.1 Starting Week 1632, Switched to IGb08 realization of the reference frame.

0.2 Starting Week 1395, adopted IGS05 for reference frame.  The combination
    is now minimum constraint.

0.3 Starting Week 1239 we adopted IGb00 reference system (given in
    IGS03P33_RS99.snx)

0.4 Starting Week 1016 we starting using ITRF97

0.5 Starting Week 0939 we starting using ITRF96 and its reference site list.  

0.6 Starting Week 0901 we started using a new apriori file not Non-ITRF94 coordinates
    based on the analysis of week 0822-0900 sinex files.  This change will 
    effect the corrdinate corrections given in this summary. 
 
1.0 Analysis Procedures:

(1) Each centers sinex solutions are de-constrained before
 combination.  When center constraints are available, the
 constraints are loosened to +-1 meters.
 
(2) Covariance matrices from each center are re-scaled based
 on the change in chi**2 when the RNAAC's sinex file is
 combined with the loose combination of the GNAAC's 
 sinex files.  To generate reasonable sigmas, the scale factor
 is set at 0.3 times the chi**2/degree of freedom increment.
 
(3) Reference frame is defined translation, rotation to the IGS14
 reference frame defined by the IGS14P_core.txt list.  List
 hierarchical.

Earth rotation parameters are estimated for each center (even when not given
in the original SINEX files.  In this case the partial derivatives are
computed from the station coordinates).

(4) The summary below gives 
    (a) The RMS difference between the GNAAC loose analysis and
the GNAAC+RNAAC loose analysis.  If this RMS is small then the 
RNAAC combination is not effecting the global coordinates solution
significiantly.
    (b) For each RNAAC Center we give:
        (b.1)  the VARIANCE rescaling factors used (determined as 
discussed above) and
        (b.2)  the adjustment to the apriori coordinates
of the sites for each RNAAC which are not included in the GNAAC
analyses.  The apriori coordinates are based on the analysis
of the first five weeks of RNAAC sinex files.  When an RNAAC
has no unique sites, the adjustments are given for all sites
in the center based on the analysis from that center alone.
 
 SUMMARY OF POSITIONS FOR WEEK 2122
 
 IMPACT OF RNAACs on GNAAC Loose solution
 
 CENTER RESULTS