We present the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry observations. ICRF2 contains precise positions of 3414 compact radio astronomical objects and has a positional noise floor of ∼40 μas and a directional stability of the frame axes of ∼10 μas. A set of 295 new "defining" sources was selected on the basis of positional stability and the lack of extensive intrinsic source structure. The positional stability of these 295 defining sources and their more uniform sky distribution eliminates the two greatest weaknesses of the first realization of the International Celestial Reference Frame (ICRF1). Alignment of ICRF2 with the International Celestial Reference System was made using 138 positionally stable sources common to both ICRF2 and ICRF1. The resulting ICRF2 was adopted by the International Astronomical Union as the new fundamental celestial reference frame, replacing ICRF1 as of 2010 January 1.

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[1] The analysis coordinator of the International VLBI Service for Geodesy and Astrometry (IVS) regularly disseminates the official IVS products of Earth orientation parameters (EOPs). For 2 years now, these parameters have been produced by combining datumfree normal equations of up to six IVS analysis centers. In this paper we document the combination methodology, discuss critical issues, and report on the quality of the products. The agreement of the very long baseline interferometry results with the International Global Navigation Satellite Systems (GNSS) Service GPS EOPs is of the order of 18 ms for length of day and 100 mas (microarc seconds) and 300 mas/d for the polar motion components and their rates, respectively.

[1] Subdiurnal periodic effects in the Earth's rotation as seen by Very Long Baseline Interferometry (VLBI) are investigated on the basis of continuous VLBI observing campaigns (CONT) observed by the International VLBI Service for Geodesy and Astrometry (IVS). In 2008, the latest campaign (CONT08) was observed adding another valuable data set of 15 consecutive days to the series of CONT sessions. Among other things, CONT08 as well as CONT02 and CONT05 had been scheduled with the aim of observing short-period variations of the Earth orientation parameters. In this publication, we describe an analysis, which is based on hourly estimates of polar motion and UT1-TAI and a subsequent spectral analysis. The generation of the time series is performed with a modified analysis approach. We add the normal equations of each individual 24 hour session to one big equation system for the whole campaign where observations of adjacent sessions contribute to parameters at session borders simultaneously. Over the years, the experience in operating and analyzing the CONT sessions has improved and the procedures have been adapted for improvement of the results. However, at the same time, the observing network has suffered considerable changes. Thus, a comparative overview over the three CONT campaigns is given in this paper. The intermittent detection of periodicities as reported by Haas and Wünsch (2006) applies in this analysis for CONT02 as well. For CONT05 and CONT08 minute signals at periods of around 6 hours are contained in the amplitude spectra. The origin of these signals is still questionable.