Submitted in response to the request of the IERS Review Board
Formed to review responses to the
Call for Participation
Issued by the
International Earth Rotation Service (IERS)
On 15 November 1999
Transmitted to Prof. Christoph Reigber, GFZ, Potsdam
On 31 May 2000
IERS Component: Conventions Product Center
Name of Organizations
Bureau International des Poids et Mesures
U. S. Naval Observatory (USNO)
Name and Title of Authorizing Officials
Dr. T.J. Quinn
Director of the BIPM
Dr. Kenneth J. Johnston
USNO Scientific Director
Dr. G. Petit, principal physicist
BIPM Time section
Dennis D. McCarthy, Director
Directorate of Time, USNO
Dr. G. Petit
BIPM, Pavillon de Breteuil
92312 Sèvres Cedex, France
Dr. Dennis D. McCarthy
U. S. Naval Observatory
3450 Massachusetts Avenue, NW
Washington, DC 20392-5420
Dr. T.J. Quinn,
Director of the BIPM
Dr. Kenneth J. Johnston
USNO Scientific Director
Dr. G. Petit, principal physicist,
BIPM time section
Dr. Dennis D. McCarthy, Director,
Directorate of Time
The Bureau International des Poids et Mesures (BIPM) and the U. S. Naval Observatory (USNO) propose to cooperate in providing the Conventions Product Center (CPC) of the International Earth Rotation Service (IERS). This activity will be carried out under the guidance of a Conventions Center Scientific Advisory Board, that will be established by the IERS Directing Board. The BIPM and the USNO jointly will
Edit the IERS Conventions, continuously maintaining the documents in electronic form and making available an updated printed version at the request of the Directing Board,
Maintain software in electronic form compatible with the IERS Conventions ,
Examine the consistency of the procedures used by the IERS analysis centers with the adopted conventions and study the impact of possible inconsistencies on the IERS products.
The Conventions and associated software will be established from the contributions of a panel of experts who will be solicited by the CPC. The contributions may be reviewed externally. Each contribution will be under the responsibility of a scientist at the CPC. The CPC scientists, in consultation with the Scientific Advisory Board, will edit the Conventions and associated software, aiming at the global consistency of the Conventions
It is expected that an updated printed version of the Conventions will be issued approximately every three years or on request of the IERS Directing Board.
DESCRIPTION OF PROPOSED ACTIVITIES
The U. S. Naval Observatory (USNO) has served the IERS by editing the IERS Standards and the successor IERS Conventions since its creation in 1988. Before the creation of the IERS the USNO published the MERIT standards. Dr. Dennis D. McCarthy served on the Project MERIT Working Group on Standards and as Editor of the IERS Standards and Conventions throughout the existence of the IERS.
The BIPM is an inter-governmental organization operating under the Convention du Mètre, signed by 48 member states. One of the tasks of the BIPM is to establish and maintain the necessary basis to ensure uniformity in measurements. In many fields of physics, this is ensured by a direct comparison of primary standards or by the establishment of procedures that allow the standards to be locally compared. For time and frequency, it has long been recognized that these comparisons can only be carried out with the help of coordinate quantities in the framework of general relativity. It is the role of the BIPM time section to establish and maintain the conventional coordinate time scale, International Atomic Time TAI, and disseminate it worldwide through the time scale UTC.
Uniformity in the definition of space reference systems is essential for all activities and techniques that use sets of measurements that are not local, which is the case of the astro-geodetic techniques contributing to the IERS. Basic metrology will also become increasingly concerned, starting with the primary frequency standards. The BIPM already maintains the coordinate time scale (TAI) used in such applications and considers that it is necessary to participate in the definition and maintenance of space-time reference systems, and in the associated work necessary to ensure their successful realization.
The BIPM and the USNO propose to cooperate in providing the Conventions Product Center of the International Earth Rotation Service. We present in Section 1 a description of the Scientific Advisory Board that is proposed to oversee the activities of the CPC, and a description of the Software Review Board. In Section 2 we outline the general policy and guidelines that define the role of the CPC. The three tasks defined for the CPC are then described.: The IERS Conventions and associated software (tasks 1 and 2) are presented in Section 3 and the studies concerning the consistent use of the Conventions are outlined in Section 4.
1. IERS Conventions Center Scientific Advisory Board and Software Review Board
The CPC will work in close cooperation with a Scientific Advisory Board. It will propose membership of this Board to the IERS Directing Board for approval. The chairman of this Board will be external to the CPC. We believe that this Board should include the IERS Analysis coordinator, representatives of the International Technique Services that contribute to the IERS, and some experts in other subject matters. One scientist from the CPC will act as the Secretary of the Scientific Advisory Board and will carry out the organizational work, ensuring continuous information of the Board members. It is expected that the Board, in addition to electronic exchange, will meet regularly (e.g. once a year).
The duties of the Scientific Advisory Board would be (1) to oversee the plans for the overall composition of the IERS Conventions proposed by the CPC, (2) to review the contents of the draft version of the Conventions for consistency and technical adequacy after editing by the CPC, and (3) to oversee studies prepared by CPC scientists regarding the consistency of procedures used by IERS Analysis Centers and review their results.
The CPC will also establish a Software Review Board. The duties of the Software Review Board would be to review contributed software for accuracy, functionality and for compliance with the proposed Conventions. The Board will assist in soliciting code from contributors, check the code for the implementation of the Conventions model and for the robustness of the software design. The Review Board will consist of experts in the fields in which the software deals.
The IERS Conventions Product Center will provide the IERS and its user community a set of conventional mathematical models and physical standards to be used in the formation and use of the products of the IERS. General guidelines proposed to define the content of the Conventions and the role of the Conventions center are:
The Conventions will be consistent with recommendations of relevant international scientific unions and represent the current state of the art. Within this general framework, they should describe the most up-to-date accepted models and numerical values of quantities.
The Conventions should state the reference systems to be used (as defined by relevant scientific unions) and provide rules on how to generate, from raw observations, IERS products consistent with the reference systems.
For the cases where some IERS centers use different models and/or reference systems, the impact on the IERS products should be studied and reported.
The Conventions should describe all that is necessary to generate the IERS products. When needed, procedures to follow in the use of the IERS products may be provided.
The Conventions will be updated regularly and provided in electronic form. As required or approximately every three years they will be compiled and provided in printed forms. Software compatible with the Conventions will also be provided electronically.
The CPC will develop a plan for the revised edition of the IERS Conventions. The Scientific Advisory Board will review this plan, making suggestions regarding contents and possible contributors.
A proposed plan for the Conventions is presented below as an example.
THE PLAN TO BE DISCUSSED SHORTLY
Following approval of the plan by the Scientific Advisory Board and the IERS Directing Board, the CPC will solicit contributions to the Conventions and edit individual contributions for language and content. It will resolve possible differences among contributors concerning content. Edited chapters will be distributed electronically to the members of the Advisory Board for final editing and review. Upon approval of the Advisory Board, the CPC will prepare a Table of Contents, Glossary, and Index, and present the final version to the IERS Directing Board for approval.
The final version of the Conventions will be made available to users electronically, and sent to a printing house for hard copy production. The CPC will maintain a distribution list for the printed copies and will mail the printed version to those on the mailing list. It will also maintain a sufficient number of copies to answer requests as they arise.
The CPC will provide both hard copy and electronic versions of the IERS Conventions. At least 500 copies will be produced for distribution. The final number of printed copies will be established in consultation with the IERS Directing Board. The electronic version will be made available on CPC computers. Mirror sites will be established at the two participating institutions.
The electronic version of the Conventions will be provided through the World Wide Web and anonymous ftp. The format of the text files will be postscript and PDF, as well as the original TeX or LaTeX files that were used to create the Conventions. Copies of the software for the IERS Conventions models will be made available. In order to facilitate access to this information, an IERS Conventions web page will be maintained by the CPC with the appropriate links to the text, software and interactive web pages. It is envisioned that the IERS Conventions will eventually exist as an HTML document that will allow easier access to the most up-to-date models and standards possible. A database of references will be established, and a search engine will be available to scan the above ensemble. A Newsgroup will allow the IERS to gather and archive users requests and responses.
Portions of the Conventions will be provided in an interactive mode. In this manner, users will be able to determine parameters of interest for particular observing locations. For example, someone in search of ocean loading tidal parameters for a site of interest will be able to use the interactive feature to calculate the parameters for that site using models and procedures described in the Conventions. It is expected that interactive software will continue to exist on the computers of those contributing the software. The IERS Conventions will make known to users the location of such software and provide the necessary electronic links in the electronic version of the Conventions.
For quick and accurate implementation of the Convention models into scientific software, the CPC will maintain standard subroutines provided by contributors implementing the Convention models. This task will be carried out essentially by USNO scientists.
Maintenance of Electronic Conventions
The CPC will maintain public access to the IERS Conventions 24 hours per day seven days per week through two mirror sites established at the BIPM and the USNO.
4. Conventions Product Center Research Projects
The CPC will undertake studies to examine the consistency of the procedures used by the IERS analysis centers with the adopted conventions and to evaluate the impact of possible inconsistencies on the IERS products. The scientists of the BIPM will carry out this work, as resources become available.
Topics will be proposed by the CPC in consultation with the IERS Directing Board. It is expected that the work will be carried out in close collaboration with relevant IERS Centers and the Analysis Coordinator. Because such studies may exceed the capacities of the CPC, they could be carried out with the help of scientists external to the CPC, for whom support could be provided. After review by the Scientific Advisory Board, the results of a study will be presented to the IERS Directing Board for their approval as a possible publication as IERS Technical Notes.
The IERS Conventions Product Center will be a joint undertaking of the BIPM and the USNO. It is envisioned that management will be cooperative and that most routine activities of the Center can be carried out independently at the two organizations.
The principal scientists of the two organizations will have overall responsibility for all aspects of the IERS Conventions Product Center. One of the principal scientists will serve as the Director of the Conventions Product Center. This responsibility will alternate between the two institutions, the change will occur every three years. The Director will be the principal point of contact for the Center, and serve as the Convention Product Center's representative on the IERS Directing Board. The USNO principal scientist will serve as the first director of the Center. They will jointly prepare proposals to the IERS Directing Board for membership on the Scientific Advisory Board and will collaborate with its chairman to organize the work . The principal scientist of the BIPM will be the first Secretary of the Board.
The principal scientists will jointly establish internal policies and operational guidelines through meetings and electronic mail. They will jointly prepare proposals for the structure and organization of revised versions of the IERS Conventions. Together with other members of the CPC they will solicit and edit contributions, and prepare the final edited version of the Conventions for approval of the Scientific Advisory Board and the IERS Directing Board. They will overview the internal research studies on the use of the Conventions in the IERS.
Dr. Elisa Felicitas Arias (BIPM) and Dr. Peter Wolf (BIPM) will assist in editing the Conventions and in the preparation of the electronic and hard copy versions. They will also be responsible for reviewing some contributions and may contribute to studies undertaken by the CPC.
Dr. Thomas Johnson (USNO) will assist in editing the Conventions and in the preparation of the electronic and hard copy versions. He will also be responsible for reviewing some contributions and testing software.
Mr. Brian Luzum (USNO) will assist in editing the Conventions and in the preparation of the final electronic and hard copy versions. He will be responsible for reviewing some contributions and the maintenance of the electronic version and the software.
Technical staff from the BIPM will develop and maintain the BIPM CPC web site and associated tools.
Assistance will be obtained from the administrative staff of the U. S. Naval Observatory as needed for production of the final copy. Printing will be carried out by means of a contract.
The electronic version and the software will be maintained on existing BIPM and USNO computers, and replacement computers will be obtained as required.
As part of its ongoing mission to provide the information necessary to use the Earth orientation data provided to its users, the U. S. Naval Observatory is committed to continue to provide funds for the operation of the CPC. This funding includes salaries of personnel, supplies, computers, computer hardware, travel and the cost of hard-copy publication. All costs for the production and maintenance of the IERS Conventions will be borne by the USNO.
The BIPM will provide funding for the operation of the CPC in salaries of personnel, supplies, computers, computer hardware and travel. CPC Scientists will provide approximately the following part of their work time: G. Petit, 35%; E. F. Arias, 20%; P. Wolf, 35%. Research Fellow positions (BIPM staff positions for a period of up to two years) may be provided, e.g. at an average level of 0.5 per year, to allow special studies to be conducted. Such positions will be provided whenever necessary to ensure the continuity of the service, in case the above mentioned participation of the BIPM staff cannot be ensured.
Office space at USNO and the BIPM and working support will be provided to occasional visiting scientists. In addition to PCs in an Intranet environment, the Center has access to a modern UNIX-type workstations, to host the Internet site. The system will be upgraded according to the general evolution of computers and software.