IGS Analysis Center Workshop - IGS - NASA

2.2 Analysis Center System DesignFigure 4 shows the activities of a GAC. Note that there is no direct link to RAC’S orNAC’s; communication of products takes place through the Data Centers.Figure 5 shows the activities of a RAC. Feedback on problems with orbits or referenceframe is sent to the data center, but it may also be sent directly to global analysis centersthrough an IGS electronic mail box. Regional data must be reduced with at least 3 stationsthat are also routinely analyzed in the global network for purposes of network combinationand quality control (allowing a check on the level of agreement between the GAC and RACsolutions of common stations). Only fiducial-free network solutions are submitted to thedata centers, with the exception of an annual regional reference frame submission which issent for assessment (by NAC’s) and for comparison with the ultimately adopted standardframe..Data CentersData ~ Orbits and EOP ~Global Analysis CentersSubmit Constrain to Partition sl# nitWe;kly standard frame ~oordinatesWeeklyMCombine into kinematic solution;apply minimal constraints SubmitAnnual Global Analysis Center*,JFigure 4. Global Analysis Center Flowchart70