Dependence of Catalogue Orientation Parameters Accuracy from Sources Set Selection 

S. Kurdubov, E. Skurikhina 
Institute of Applied Astronomy RAS, Russia

Oral presentation 

This study is devoted to selection of the set of sources which by the best way defines the orientation parameters of the one catalogue relative to another in case of rigid rotation model. Formal errors of the transformation parameters were selected as characteristic of the sources set. Special algorithm for the sources set selection was suggested: at first we select three sources which will minimize the maximal value of the transformation parameter error. Then we consistently add to one source from the all set and find the source minimized the transformation parameter error. We repeat this procedure for all sources. Then we obtained transformation parameters accuracy as function of the number of sources for the 5 catalogues of the IVS WG.  For all catalogues this function has a minimum between 300 and 400 sources, adding the sources after the minimum leads to increasing formal errors of orientation parameters. After that we selected the common sources that placed before minimum of functions for all 5 catalogues and obtained set of 319 sources. The catalogue with selected sources set as NNR was calculated. Then the nutation scatter test was applied to this catalogue.