10:30 AM - 10:45 AM
[G01-2-01] Progress towards the third realisation of the International Celestial Reference Frame
invited
The presentation will review the progress towards the generation of the third realization of the International Celestial Reference Frame. The work for ICRF3 is carried out by a Working Group of the IAU with the aim of completing ICRF3 by 2018 for adoption at the IAU General Assembly in Vienna. ICRF3 will be based on state-of-the-art astronomical and geophysical modeling and will benefit from the wealth of VLBI data acquired since ICRF2 was built in 2009 (an additional 60% of data). Areas of work include selecting the datasets, defining the analysis configuration, identifying the stable sources, identifying the ICRF2 to ICRF3 transfer sources, and selecting defining sources for ICRF3. The latter takes advantage of the many VLBI images available to derive source structure indices which provide a mean to assess the astrometric quality of the sources. Specific attention will be paid to the treatment of Galactic aberration which affects VLBI data at a significant level due to the > 30 yr time-baseline. Besides the standard S/X band observations (2.3/8.4 GHz), data at K band (24 GHz) and X/Ka band (8.4/32 GHz) are being considered, while the recent Gaia Data Release (DR1) provides a unique check against optical positions. Finally, an additional stage which combines rigorously individual solutions into a consolidated VLBI catalog is also investigated.