The International Earth Rotation Service (IERS) was established in 1987 by IAU and IUGG and it started operation on 1988 January 1st. It replaces the International Polar Motion Service (IPMS) and the earth-rotation section of the Bureau International de l'Heure (BIH); the activities of BIH on time are continued at Bureau International des Poids et Mesures (BIPM). IERS is a member of the Federation of Astronomical and Geophysical Data Analysis Services (FAGS).

IERS should provide the information necessary to define a Conventional Terrestrial Reference System and a Conventional Celestial Reference System and relate them as well as their frames to each other and to other reference systems used in the determination of the earth orientation parameters.

IERS is responsible for :

- defining and maintaining a conventional terrestrial reference system based on observing stations that use the high-precision techniques in space geodesy;

- defining and maintaining a conventional celestial reference system based on extragalactic radio sources, and relating it to other celestial reference systems;

- determining the earth orientation parameters connecting these systems, the terrestrial and celestial coordinates of the pole and universal time;

- organising operational activities for observation and data analysis, collecting and archiving appropriate data and results, and disseminating the results to meet the needs of users.

IERS consists of a Central Bureau and Coordinating Centres for each of the principal observing techniques, and is supported by many other organisations that contribute to the tasks of observation and data processing.

The Coordinating Centres are responsible for developing and organising the activities in each technique to meet the objectives of the service. The Central Bureau combines the various types of data collected by the service, and disseminates to the user community the appropriate information on earth-orientation and the terrestrial and celestial reference systems. It can include sub-bureaux for the accomplishment of specific tasks. The Central Bureau decides and disseminates the announcements of leap seconds in UTC and values of DUT1 to be transmitted with time signals.

The Directing Board is composed of representatives of

- the International Astronomical Union

- the International Association of Geodesy/International Union of Geodesy and Geophysics

- the Federation of Astronomical and Geophysical Data Analysis Services

- the Central Bureau

- each of the Coordinating Centres

The chairperson is a member of the Directing Board, elected by the Board for a term of four years, with the possibility of reelection for one additional term. He/she coordinates the activity of the Directing Board. He/she is the official representative of the Service at the meetings of IAU, IAG/IUGG, FAGS, and other outside organisations.

The Directing Board exercises general control over the activities of the service, including modifications to the organisation and participation that would be appropriate to maintain efficiency and reliability, while taking full advantage of the advances in technology and in theory. Most decisions are expected to be made by consensus or by a simple majority vote. Changes in the structure, membership and chairmanship of the Directing Board can be made at any time by a two third majority.

The secretariat of the Board is provided by the Central Bureau. The function includes the distribution of papers and the compilation of the annual administrative and financial reports.

The Board shall meet annually and at such other times as shall be considered appropriate by the Chairperson or at the request of two members.

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