Scientific Rationale
During the last IAU General Assembly much progress has been reported in JD7 "Space-time reference systems for future research", and also at the Division 1 meetings. The topics included theoretical aspects of reference systems, requirements on space-time reference systems for future space missions, advanced dynamical models for the solar system, time and frequency transfer, Earth rotation modelling, astrometric catalogues, ephemerides, atomic time, pulsar-based timescale, etc.

Many of these topics have been identified as being important for furthering our scientific understanding of the issues and will form the core of the discussions during the Journees. In addition, the various new working groups (ICRS, UTC, pulsar time, nomenclature, Earth rotation modelling, etc.), which are all relevant to the field of the Journées, will also have much to contribute.

The scientific programme of the Journées 2013 will include sessions on the scientific developments in geodesy, astronomy and astrophysics, etc. based on highly accurate reference frames and time scales. In addition, there will be presentations and discussions related to the new IAU Division A Working Groups that have been established at the 28th IAU GA.

Tutorial lectures will be held the day before the beginning of the Journées with the goal of making our discipline more broadly accessible.