On weighting of astrometric VLBI observations

Abstract

In this paper, results are presented of a study performed to investigate the impact of the cut-off elevation angle(CEA) and elevation-dependent weighting(EDW) on the Earth orientation parameters (EOP) and baselinelength estimates obtained from astrometric and geodetic VLBI observations. For this test, 2-week continuous CONT05 VLBI observations were processed with different CEA and EDW settings, keeping all other options the same as for routine data processing. For the baseline length, the repeatability test was used toinvestigate the impact of the analysis options under investigation. For EOP, the uncertainties and correlations between estimated parameters are investigated, as well the differences between VLBI and GPS results obtained during the CONT2005 period. The study shows that applying a small CEA up to about 8-10 degrees does not have a major impact on the results, except for a small degradation of baseline length repeatability. On the other hand, applying EDW allows one to obtain smaller errors for the baseline length, polar motion and UT1. No substantial impact was found on the celestial pole offset. Finally, we conclude that inclusion of low-elevation observations, properly weighted, improves the baseline length repeatability and EOP results.

Keywords:

VLBI, Earth orientation parameters, baseline length, weighting