IGS Analysis Center Workshop - IGS - NASA

LbPIERS and IGSCentral Bureausand Designatesfeedback L ~-“K 7 feedbackGlobal AnalysisCenters (GAC’S)IIfeedbackE Regional AnalysisCenters (RAC’S)vIlr--GDJ-LFigure2. Distributed system design that builds ontheexisting system mdembodies thebasic ideas that were shown in Figure 1.(ii) Regional Analysis Centers (RAC’S) will analyze specific regional cluster(s) ofstations following certain standards and flexible guidelines. RAC’s will providefiducial-free network solutions to IGS, but are of course free to impose any constraintthey wish for their own research and internal purposes. IGS will provide the means forRAC’S to impose meaningful constraints for this purpose (see below).(iii) Network Analysis Centers (NAC’S) will take RAC and GAC daily free-networksolutions as input and produce combined solutions for reference frame investigations,quality assessment, feedback to RAC’S and GAC’S, and to submit findings to the IGSCentral Bureau who will then work with the NAC’S and the I13RS Central Bureau toproduce an annual update to the standard frame (to be then used by GAC’S fororbitlEOP production, and by RAC’s and other customers for network constraints). ANAC has no obligation to look at all available solutions. Indeed, a NAC mightroutinely only combine one RAC solution with one GAC solution. This flexibilitymight encourage more NAC’S to get involved in the hope that it will result in morecoordinates. Two (minor and acceptable) consequences are that the “daily” solutions will (1) be slightlysmoothed to the degree that neighboring solutions use common data, and (2) have slightly differentsensitivity to systematic errors.66