by Erwin Groten, President of SC 3 of IAG


At the General Assembly at Kyoto in 1997 the IAU Working Group on Astronomical Systems (WGAS) has created two new subgroups, the SOFA Subgroup chaired by P. Wallace and the Fundamental Constants Subgroup chaired by D. McCarthy.

Besides this, the working group on Celestial Reference Frames (chairman: L. Morrison) has concentrated on the implementation and definition of extraterrestrial frameworks and systems which became more or less pure space systems without fundamental relations to terrestrial parameters. The working group on nutation and other terrestrial parameters (such as precession etc.) under the guidance of V. Dehant and others as well as the working group on relativistic (chairman: G. Petit), mainly post-Newtonian, systems, their exact definition, implementation and realization have been active but a new complete and relativistic high-precision reference system is not expected to be available prior to the next General Assembly of the IAU. The IERS Editorial Board under the guidance of the IERS Directing Board is editing at three years intervals the IERS-Conventions in close relationship with IAU working groups and Special Commission 3 (Fundamental Constants) of IAG. IERS Conventions gained wide interest recently in view of its extended impact, besides other and related systems of global fundamental interest such as ITRS, IGS, ETRF(S), ICET.

In spite of the progress made since the last General Assembly of IUGG at Boulder (1995) and the General Assembly of IAU at Kyoto (1997) in various fields there is no official change of fundamental formulas (nutation etc.), fundamental systems or fundamental constants. Special Commission 3 has updated its „current best estimates" of fundamental parameters, also by including improved gradients (changes of „constants" with time). Most other groups proceeded in a similar way, without changing the official values even though there is general agreement on the need for such changes. For the year 2001 at the next IAG General Assembly official systems are expected to change significantly, IERS-Conventions 2000 are under consideration.

In view of greater impact of improved global reference systems on high-precision terrestrial and space applications there is increasing activity at related institutes of interest such as BIPM, Bureau de Longitude, GFZ, with the aim to play more substantial roles in related fields. Moreover, there are clear tendencies to interrelate the principal organizations and working groups. IAG and IUGG should pay more attention to these tendencies in order to make sure that IAG and IUGG remain in the focus of new developments. Also within IAG there should be an improved transfer structure in order to guarantee that the „know-how" and competence is used, and the interest of IAG and IUGG is well represented in the related organizations. Recently, the traditional interrelation of IAU and IAG were mainly limited to IERS; it would be to the benefit of both organizations and the two unions to maintain the earlier broader connections between IAU and IAG. The intensive exchange of updated versions of official catalogues, the interchange and discussion of forthcoming results, such as „current best estimates", besides official parameters and the reconciliation of interests (by electronic mail and other means) would be very valuable.