Jan Vondrak, Chairman of the Directing Board
After ten years of activity it became necessary to reorganize
the IERS for various reasons: the re-organization of the space techniques SLR,
Lunar Laser Ranging, VLBI, and GPS into International Services (DORIS being now
organized as a pilot program) and the development of a new component: the
Global Geophysical Fluids Center (GGFC) dealing with motion of the various
fluid layers and their relationship with reference frames and Earth dynamics.
The re-organization of the Service began in November 1999, when the Call for
Participation was issued. The Letters of Intent were reviewed by the IERS
Directing Board (DB) at its meeting in December 1999 (San Francisco). It was
decided to set up a Proposal Review Committee (PRC) with the task to evaluate
all proposals and prepare the corresponding recommendations for the next IERS
DB meetings. The PRC was composed of knowledgeable scientists, under the chair
of I.I. Mueller, at the beginning of 2000. Its first recommendations were
discussed at the IERS DB meeting in Washington (June 2000), and some of them
accepted. Nevertheless, there were still several multiple proposals for the
same components. The primary scientists of these were further contacted by the
PRC and, in some cases, new joint proposals were asked for. The IERS DB was
able to take final decisions at its meeting in Frankfurt a.M. (September 2000).
Several minor changes of the Terms of Reference were adopted by the 'old'
Directing Board at its last meeting in San Francisco (December 2000), mainly
reflecting a slightly changed structure of the ITRS Product Centers. The new
structure of the IERS began operation on January 1, 2001.
The main changes in IERS structure are: The previous
Sections and Sub-Bureaus of the Central Bureau are now autonomous components
within the IERS and are called Product Centers; The Central Bureau moved from
Paris to Frankfurt am Main in Germany and has now primarily administrative
functions; New elements of the structure are Combination Research Centers, ITRS
Combination Centers and the Analysis Coordinator; External International Services
(like IGS, ILRS and IVS) serve as Technique Centers of the IERS.
According to the IERS Terms of Reference, the primary
objectives of the IERS are to serve astronomical, geodetic and geophysical
communities by providing: International
Celestial Reference System and Frame (ICRS, ICRF); International Terrestrial
Reference System and Frame (ITRS, ITRF); Earth Orientation Parameters (EOP)
that define the transformation between the ICRS and ITRS; Relevant geophysical
data (i.e., information on the distribution and motion of the atmosphere,
terrestrial and oceanic water, mantle, core...); Conventions (i.e., standards,
constants, models, algorithms, software...).
To cover this broad field of interest and to realize
the products, the new IERS Terms of Reference define the following components
of the new IERS:
Technique Centers (TC) that are generally autonomous
independent services, cooperating with the IERS. There is typically only one TC
per technique, and it provides its operational products to the IERS. At the
moment, these are the following: International VLBI Service (IVS);
International GPS Service (IGS); International Laser Ranging Service (ILRS);
International DORIS Service (IDS) that has however not yet been formed; the
technique serves as a Pilot Experiment of the CSTG.
Product Centers (PC) that are responsible for the
products of the IERS. They are: Earth Orientation PC, responsible for
monitoring long-term orientation parameters, publications for time
dissemination and announcements of leap seconds. It is located at Observatoire
de Paris. Rapid Service/Prediction PC, responsible for providing Earth
orientation parameters on a rapid basis, primarily for real-time users. It is
placed at U.S. Naval Observatory, Washington D.C. Conventions PC is responsible
for the maintenance of the IERS conventional models, constants and standards.
Joint proposal of U.S. Naval Observatory (Washington D.C.) and Bureau
International des Poids et Mesures (Sèvres) was accepted. International
Celestial Reference System PC, responsible for the maintenance of ICRS and its
realization, ICRF. Joint proposal of Observatoire de Paris and U.S. Naval
Observatory was accepted. International Terrestrial Reference System PC,
responsible for the maintenance of ITRS and its realization, ITRF. It is
located at IGN, Marne-la-Vallée. Global Geophysical Fluids PC, responsible for
providing relevant geophysical data sets and related results. This center now
consists of eight Special Bureaus (for Atmosphere, Core, Gravity/Geocenter,
Hydrology, Loading, Mantle, Oceans, and Tides), and is hosted at NASA's Goddard
Space Flight Center.
Combination Centers: ITRS Combination Centers,
responsible for providing ITRF products by combining ITRF inputs from the
Technique Centers and other sources. Three institutions established ITRS
Combination Centers: DGFI, Munich, Germany; Geomatics Canada, Ottawa, Canada;
IGN, Marne-la-Vallée, France. Combination Research Centers, responsible for the
development of combinations from data (or products) coming from different
techniques. They are expected to provide their solutions to Analysis
Coordinator. There are now eleven of them AICAS & CTU, Prague, Czech R.;
FGS & DGFI, Munich, Germany; FGS & FESG, Munich, Germany; FGS &
GIUB, Bonn, Germany; GFZ, Potsdam, Germany; FFI, Kjeller, Norway; GRGS,
Toulouse, France; IGN, Marne-la-Vallée, France; JPL, Pasadena, USA; IAA, St.
Petersburg, Russia; ASI, Matera, Italy.
Analysis Coordinator (Markus Rothacher, TU Munich,
Germany) is responsible for long-term and internal consistency of the IERS
reference frames and other products, for ensuring the appropriate combination
of the TC products into a single set of official IERS products and for
archiving them.
Central Bureau (placed at BKG, Frankfurt a. M.,
Germany, under the direction of Bernd Richter) is the administrative center of
the IERS. It is responsible for the general management (according to the
directives given by the Directing Board), for coordinating the activities, IERS
publications, archiving the products and it also serves as the communication
center with the users. The CB presently designs a data center to store and
archive all products which are necessary for the IERS products and also those
which are necessary to re-compute the products.
Directing Board that exercises general control over
the activities of the IERS. The chairperson, elected by the Board from its
members (Jan Vondrák, Astronomical Institute, Academy of Sciences of the Czech
Republic, Prague), is the official representative of the IERS to external organizations.
The DB consists of two representatives of each of the Technique Centers, one
for each of the Product Centers, one for all Combination Research Centers
together, a representative of the Central Bureau, Analysis Coordinator, and the
representatives nominated by the IAU, IAG/IUGG and FAGS.
The IERS DB in its new composition met at least twice
a year: Meeting No. 30 in Washington, June 3-4, 2000; No. 31 in Frankfurt a.M.,
September 14-15, 2000; No. 32 in San
Francisco, December 18, 2000; No. 33 in
Nice, March 26, 2001; No. 34 in
Brussels, September 26, 2001; No. 35 in Paris, April 20, 2002; No. 36 in Munich, November 22, 2002;
and No. 37 in Paris, April 2, 2003 to
decide on important matters of the Service like structural changes, overall
strategy, creating working groups, launching projects, changing Terms of
Reference, etc.
The IERS organized two Workshops and a Retreat: The
first was the IERS Workshop on the Implementation of the IAU 2000 Resolutions
(Paris, April 18-19, 2002). It included detailed presentations and explanations
of the contents of the Resolutions, the background reasons for their adoption,
associated concepts and implementations as well as answers to specific
questions. About 80 participants from 20 countries took part in the meeting.
The Proceedings were printed as IERS Technical Note No. 29 and are available
also online through IERS's website. The results of this workshop are, to some
extent, reflected in IERS Conventions 2000, and also in new IERS products
(celestial pole offsets referred to new precession-nutation model IAU2000A),
published since the beginning 2003. The
second workshop was the IERS Workshop on Combination Research and Global
Geophysical Fluids (Munich, November 18-21, 2002). Its main goal was to improve
all IERS products in accuracy, consistency, stability, timeliness,
user-friendly access, and documentation, and to make first steps towards a
rigorous combination of the various products, contributing thus significantly
to the realization of an "International Global Geodetic Observation
System" (IGGOS). The workshop was divided into two strongly related parts:
different aspects of the comparison and combination of the results of all major
space geodetic techniques; IERS Global Geophysical Fluid Center (GGFC), the
present status of its products and its role in future. The Proceedings of this
Workshop will be published as IERS Technical Note No. 30.
The IERS Retreat (Paris, March 31 - April 1, 2003)
was summoned to review the present and propose future IERS products, ensure
their better mutual consistency, to specify the IERS requirements and to
develop a vision for the future. Discussion on possible organizational
consequences led to the concrete proposals for the DB meeting that immediately
followed the Retreat.
Among the most important decisions made by the DB in 2000-2003 belong: Creation of the new ITRS Combination Center in Canada; Creation of the new GGFC Special Bureau for Loading; Creation of the new Combination Research Center in Italy; Decision to contribute to the prepared IAG Pilot Project IGGOS; Launching the IERS Combination Pilot Project; Establishment of Working Groups: on Combination, the ITRF datum, and Site co-location; Changing the name to International Earth rotation and Reference systems Service, without changing the acronym (IERS).