Activity Report for 1999-2000 of the International Centre for Earth Tides (ICET)
B.Ducarme, ICET Director
ducarme@oma.be

The staff of ICET, which is completely supported by the Royal Observatory of Belgium, is composed as follows:

Prof. B.Ducarme, Director (part time)
Mrs. L.Vandercoilden, technician (full time)
Mr. M.Hendrickx, technician (part time)

The Royal Observatory of Belgium is hosting ICET since 1958 and continues to provides numerous administrative and scientific facilities especially for the publication of the “ Bulletin d’Information des Marées Terrestres” , for the tidal data processing and more recently for the maintenance of the ICET/GGP data base..


1. Ongoing activities

The tasks of the Centre are continuously updated and ICET decided :

• To become the computing centre and the data bank of the Global Geodynamics Project (GGP) which is a six years world wide campaign of tidal gravity observations using a network of more than 15 cryogenic gravimeters (figure 1).

• To organise training sessions in tidal data preprocessing and analysis using up to date software and procedures, and to improve the diffusion of these software.

• To develop its web page www.astro.oma.be/ICET/

As the groups interested by tidal phenomena are always very small and often only marginally involved in tidal research and as the papers dealing specifically with tidal studies are not fitting so well to international journals, it is still very important to keep a specialised diffusion and information medium. It is the vocation of the “Bulletin d’Information des Marées Terrestres” (BIM). ICET is publishing two eighty-pages issues per year. Starting from BIM 133 an electronic version is available from ICET web site.
We receive regularly requests for information. The most common requests concerns tidal predictions or general information. We receive more or less one request per week. Since ICET is charged, thanks to Marion Wenzel courtesy, to distribute freely the ETERNA34 tidal analysis package we had to sent 40 copies of the CD-rom within the first year.


2. The 14th International Symposium on Earth Tides 

ICET Director presented his report to the Earth Tides Commission (ETC) at the 14th International Symposium on Earth Tides (ETS2000) which took place at Mizusawa (Japan) from August 28 to September 1st. The ICET Directing Board met on August 29 under the chairmanship of Prof.S.Takemoto, ETC President. Unhappily several members were not present. Following the decease of Prof. H.G.Wenzel, it was decided to propose the cooptation of additional members i.e. Prof. R.Vieira Diaz from Spain and Dr. H.Schuh from Austria. The main subject of discussion was the proposal of creating a new confederated service inside IAG (see point7).


3. Visitors

Dr. Mark Davis from the Open University, Great Britain came one week in May 2000 to get training on tidal data preprocessing and analysis. He brought with him the tidal gravity observations registered on Mount Etna. His main goal is to get rid from tidal, pressure and other environmental effects in order to try to identify the effects of volcanic activity on the gravity residuals.

Dr. G. Casula was staying two weeks in June 1999. He brought his data of the Brasimone cryogenic gravimeter in order to practice with T-soft and the new softwares of Prof. A.P. Venedikov.

Dr. H.P.Sun stayed at ROB from beginning of September to end of November 2000. He treated the observations obtained at the GGP station Wuhan using T-soft. In collaboration with B.Ducarme he prepared a paper “Tidal Gravity Results from GGP Network in Connexion with Tidal Loading and Earth Response” that has been presented at ETS2000 and published in its Proceedings.

Dr. V.Timofeev stayed at ROB from October 20 to December 23, 1999. During these two months at ROB we finished the analysis of the tidal data recorded at Talaya, (Baikal, Siberia) and at Ala-Archa/Bishkek (Kirghizstan). At Talaya we have now analysed ten years (1988-1998) of clinometric records in NS and EW direction as well as five extensometers. Three papers have been published in BIM133.

Dr. Alexander Kopaev from Sternberg Astronomical Observatory, Moscow University, stayed one month in March 2000 to work on the ICET data bank. One paper is published in ETS2000 Proceedings.

Prof. David Crossley and Jacques Hinderer, respectively President and Secretary of the GGP consortium, visited ICET to discuss of the current status of the GGP data bank at ICET. They met Dr. Bernd Ritschel who is developing the GGP data base software.

Dr. Ernst Boyarski and Ludmila Latinina, from Institute of Physics of the Earth of Moscow were staying one week in September 2000. They brought clinometric and extensometric data from stations Medevo/Almaty (Kazakstan) Protvino/Serpoukov (Russia). They got training in recent tidal analysis methods.


4. Data processing

Several Institutes continue to send regularly earth tides data to ICET. All data received have been checked and recompiled. East European countries are still sending clinometric and extensometric records but most of the activity is now devoted to gravity tides. Most of our computing activities are now connected to the GGP project.
According to the internal GGP rules we produced already the 4 CD-ROMS containing the raw (#1 and #2) and processed (#1a and #2a) minute data of the two first years, 97/07 to 99/07, of the project. The CD-ROM of the third year is due on July 2001.


5. Web site

ICET Web site has been updated and developed. Besides general information including historical aspect and last ICET reports, it proposes to the visitors an access to:

• the general bibliography on Earth Tides from 1870-1997 either by alphabetical order of the first author or following the decimal classification introduced by Prof. P.Melchior

• the table of content of the most recent issues of the BIM and, starting from BIM 133, an electronic version of the papers
  

• tidal analysis and preprocessing softwares available from different Web sites or on request from ICET.

6. New structures inside IAG

In the framework of the reorganisation of the IAG structures a proposal has been put forward by Prof. F.Sanso, Director of the IGeS to create a confederation of the IAG Services dealing with the gravity vector i.e. the International Centre for Earth Tides (ICET), the International Gravimetric Bureau (IGB) and the International Geoid Service (IGeS). A draft proposal was established during meetings of the three directors in Milan on May 3, 2000 and on March 22nd in Nice. Other entities could join this group. The proposed name of this new composite body is Gravity Field and Figure of the Earth Service (GFFS).

As the statutes of the contributing entities are very different, some being FAGS member or WDC other not, each partner will keep his own governing bodies and structures. There will be an « Advisory board » organising the co-operation between Centres and their representation at IAG level. Individuals wishing to contribute actively to the GFFS may obtain the status of « Fellows » and will be represented inside the Advisory Board. 

The Directing board of ICET agreed on the principle of joining GFFS. The same holds for IGB and IGeS. The IAG Executive Committee set up a provisory board to report at the General Assembly in Budapest.

As a first action ICET was decided to organise jointly with IGB a summer school on gravity measurements and data processing, including the tidal signal.