The ICRF-3: Proposed Roadmap to the Next Generation International Celestial Reference Frame

ICRF-3 seeks to improve upon the highly successful ICRF-2. Our goals are to improve the precision, spatial and frequency coverage relative to the ICRF-2 by 2018. This date is driven by the desire to create radio frames that are ready for comparison with the Gaia optical frame.

Several specific actions are underway. A collaboration has started to improve at S/X-band precision of the VLBA Calibrator Survey's ~2200 sources which are typically 5 times less precise than the rest of the ICRF-2. S/X-band southern precision improvements are underway with observations using southern antennas such as the AuScope and HartRAO, S. Africa.

We also seek to improve radio frequency coverage with X/Ka and K-band work. An X/Ka frame of 654 sources now has full sky coverage from the addition of a 2nd southern station in Argentina which should strengthen the southern hemisphere in general. A K-band collaboration has formed with similar coverage and southern precision goals.

On the analysis front, special attention is being given to combination techniques both of VLBI frames and of multiple data types. Consistency of the CRF with the TRF and EOP is another area of concern. Comparison of celestial frame solutions from various groups is underway in order to identify and correct systematic errors.

Finally, work is underway to identify and pinpoint sources bright enough in both radio and optical to allow for a robust frame tie between VLBI and Gaia optical frames.