International VLBI Service
for Geodesy and Astrometry

TERMS OF REFERENCE


October 20, 1998

SUMMARY
  1. Objectives
  2. Data Products
  3. Research
  4. Components
  5. Coordination
COMPONENTS
  1. Network Stations
  2. Operation Centers
  3. Correlators
  4. Analysis Centers
  5. Data Centers
  6. Technology Development Centers
  7. Coordinating Center
COORDINATORS
  1. Technology Coordinator
  2. Network Coordinator
  3. Analysis Coordinator
DIRECTING BOARD
  1. IVS Associate Members
  2. Correspondents


1. SUMMARY

1.1 Objectives

The International VLBI Service for Geodesy and Astrometry (IVS) is an international collaboration of organizations which operate or support Very Long Baseline Interferometry (VLBI) components. The primary objective of IVS is to foster VLBI programs as a joint service to support geodetic, geophysical, astrometric, and other research and operational activities. This is accomplished through close coordination to provide high-quality VLBI data and products.

The second objective of IVS is to promote research and development activities in all aspects of the geodetic and astrometric VLBI technique. This objective also supports the integration of new components into IVS. The further education and training of VLBI participants is supported through workshops, reports, electronic network connections, and other means.

The third objective of IVS is to interact with the community of users of VLBI products and to integrate VLBI into a global Earth observing system. IVS interacts closely with the International Earth Rotation Service (IERS) which is tasked by the IAU and IUGG with maintaining the international celestial and terrestrial reference frames and with monitoring Earth rotation.

To meet these objectives, IVS coordinates VLBI observing programs, sets performance standards for VLBI stations, establishes conventions for VLBI data formats and data products, issues recommendations for VLBI data analysis software, sets standards for VLBI analysis documentation, and institutes appropriate VLBI product delivery methods to ensure suitable product quality and timeliness. IVS closely coordinates its activities with the astronomical community because of the dual use of many VLBI facilities and technologies for both astronomy and astrometry/geodesy.

IVS accepts observing proposals for research and operational programs that conform to the IVS objectives.

1.2 Data Products

VLBI data products contribute uniquely to these important determinations:

These results are the foundation of many scientific and practical applications requiring the use of an accurate inertial reference frame, such as high-precision navigation and positioning. IVS provides, through the collaborative efforts of its components, a variety of significant VLBI data products with differing applications, timeliness, detail, and temporal resolution, such as: All VLBI data products are archived in IVS Data Centers and are publicly available.

1.3 Research

The VLBI data products are used for research in many related areas of geodesy, geophysics, and astrometry, such as:

To support these activities, there are ongoing research efforts whose purpose is to improve and extend the VLBI technique in such areas as:

Components

IVS acquires VLBI data, correlates the data, analyzes the data to produce geodetic, astrometric, and other results, and archives and publicizes data products. IVS accomplishes its goals through the component described in the next section. IVS will accept proposals at any time for any of its components. Such proposals will be reviewed by the Directing Board. The IVS components are the following:

Coordination

Specific activities for technology, network data quality, and data products are accomplished through the functions performed by three coordinators:

2. COMPONENTS

IVS acquires VLBI data, correlates the data, analyzes the data to produce geodetic and astrometric results, and archives and publicizes data products. IVS accomplishes its goals through the components described below.

2.1 Network Stations

The IVS observing network consists of high performance VLBI stations.

2.2 Operation Centers

The IVS Operation Centers coordinate the routine operations of one or more networks. Operation Center activities include:

IVS Operation Centers follow guidelines from the Coordinating Center for timeliness and schedule file formats. Operation Centers cooperate with the Coordinating Center in order to define:

2.3Correlators

The IVS Correlators process raw VLBI data and station log files following a data acquisition session. Their other tasks are to:

2.4 Analysis Centers

The IVS coordinates VLBI data analysis to produce high-quality results for its users. These activities are performed by Analysis Centers, which contribute to the IVS core products, and by Associate Analysis Centers, which contribute other specialized products. Two types of Associate Analysis Centers are recognized: Global and Special.

The Analysis Centers receive and process VLBI data from one or more IVS Data Centers and are committed to produce the core products, without interruption, and at a specified time lag to meet IVS requirements. The IVS core products, at a minimum, consist of Earth orientation parameters, station coordinates, and source coordinates. The Analysis Centers place their final results in IVS Data Centers for dissemination to researchers and other users. They adhere to IVS recommendations for the creation of high-quality products and their timely archiving and distribution. Any deviations that an Analysis Center makes from IVS recommendations are properly documented. Analysis Centers provide timely feedback about station performance.

The Global Associate Analysis Centers process all the observed VLBI data. Some process data directly from Correlators and then make available as products the final VLBI database files and SINEX files. Others start with these database to perform their analyses, but will process all the databases.

The Special Associate Analysis Centers analyze selected databases for one (or more) specific interests, such as regional data processing, terrestrial reference frame maintenance, or Earth orientation results.

In addition, all types of IVS analysis centers satisfy the following standards:

2.5 Data Centers

The IVS Data Centers are repositories for VLBI observing schedules, station log files, and data products. Data Centers may mirror other Data Centers to make the distribution and maintenance of data more efficient and reliable.

Data Centers provide the following functions:

2.6 Technology Development Centers

The IVS Technology Development Centers contribute to the development of new VLBI technology. They may be engaged in hardware and/or software technology development, or evolve new approaches that will improve the VLBI technique and enhance compatibility with different data acquisition terminals. They will:

2.7 Coordinating Center

The IVS Coordinating Center is responsible for coordination of both the day-to-day and the long-term activities of IVS, consistent with the directives and policies established by the Directing Board. Specifically, the Coordinating Center monitors, coordinates, and supports the activities of the Network Stations, Operation Centers, Correlators, Data Centers, Analysis Centers, and Technology Development Centers. The Coordinating Center works closely with the Technology Coordinator, the Network Coordinator, and the Analysis Coordinator to coordinate all IVS activities.

The primary functions of the Coordinating Center are to:

Through a reciprocity agreement between IVS and IERS the Coordinating Center serves as the VLBI Coordinating Center for IERS, and as such its designated representative, subject to the Directing Board approval, is a member of the IERS Directing Board. Such a representative is a non-voting member of the IVS Directing Board. In turn, the IERS Directing Board designates a representative to the IVS Directing Board. This arrangement is to assure full cooperation between the two services.

3. COORDINATORS

3.1 Technology Coordinator

The IVS Technology Coordinator is selected by the Directing Board from responses to an open solicitation to the IVS Technology Development Centers. The Technology Coordinator is responsible for coordinating the new technology activities of IVS and for stimulating advancement of the VLBI technique. The Technology Coordinator performs the following functions:

The Technology Coordinator works closely with the astronomical community because of the many parallels between the technology development required for both groups.

3.2 Network Coordinator

The IVS Network Coordinator is selected by the Directing Board from responses to an open solicitation to all IVS components. The Network Coordinator represents the IVS Networks on the Directing Board and works closely with the Coordinating Center. The Network Coordinator is responsible for stimulating the maintenance of a high quality level in the station operation and data delivery. The Network Coordinator performs the following functions:

The Network Coordinator works closely with the geodetic and astronomical communities who are using the same network stations for observations. The Coordinator takes a leading role in ensuring the visibility and representation of the Networks.

3.3 Analysis Coordinator

The IVS Analysis Coordinator is selected by the Directing Board from responses to an open solicitation to the IVS Analysis Centers. The Analysis Coordinator is responsible for coordinating the analysis activities of IVS and for stimulating VLBI product development and delivery. The Analysis Coordinator performs the following functions:

The Analysis Coordinator works closely with the geodetic and astronomical communities who are using some of the same analysis methods and software. The Analysis Coordinator plays a leadership role in the development of methods for distribution of VLBI products so that the products reach the widest possible base of users in a timely manner. The coordinator promotes the use of VLBI products to the broader scientific community and interacts with the IVS Coordinating Center and with the IERS.

4. Directing Board

The Directing Board determines policies, adopts standards, and approves the scientific and operational goals for IVS. The Directing Board exercises general oversight of the activities of IVS including modifications to the organization that are deemed appropriate and necessary to maintain efficiency and reliability.

A specific function of the Board is to set scientific goals for the IVS observing program. The Board will establish procedures for external research programs and will review any proposals thus received.

The Board may determine appropriate actions to ensure the quality of the IVS products and that the IVS components maintain the adopted standards.

The Directing Board consists of appointed members who serve ex officio, members elected by the Directing Board, and members elected by the IVS components. The members are:

Appointed members ex officio:

Selected by Directing Board upon review of proposals from the relevant IVS component (see below):

Elected by Directing Board upon recommendation from the Coordinating Center (see below):

Elected by IVS Components (see below):

Total number:    14

The four appointed members are considered ex officio and are not subject to institutional restrictions. The other 10 persons must be members of different IVS components. At-large members are intended to ensure representation on the Directing Board of each of the components of IVS and to balance representation from as many countries and institutions as possible. All elected members serve staggered four-year terms once renewable.

Election of Board members by the IVS components shall be conducted by a committee of three Directing Board members, the chair of which is appointed by the chair of the Directing Board. The committee solicits nominations for each representative from the relevant IVS components. Networks representatives can be nominated by well-defined, operating networks accepted as such by the Directing Board. For each position, the candidate who receives the largest number of votes from the Associate Members will be elected. In case of a tie the Directing Board will make the decision.

The chair is one of the Directing Board members and is elected by the Board for a term of four years with the possibility of reelection for one additional term. The chair is the official representative of IVS to external organizations.

Most decisions by the Board are made by consensus or by simple majority vote of the members present. In case of a tie, the chair shall vote but otherwise does not vote. If a two-thirds quorum is not present, the vote shall be held later by electronic mail. A two-thirds vote of all Board members is required to modify the Terms of Reference, to change the chair, or to change any of the members elected by the Directing Board before the normal term expires.

The Board meets at least annually, or more frequently if meetings are called by the chair or at the request of at least three Board members. The Board will conduct periodic reviews of the IVS organization and its mandate, functions, and components. The reviews should be done every four years.

The Secretariat of the Directing Board is provided by the Coordinating Center.

4.1 IVS Associate Members

Individuals affiliated with organizations that participate in any of the IVS components may become IVS Associate Members. Associate Members are generally invited to attend non-executive sessions of the Directing Board meetings with voice but without vote. Associate Members take part in the election of the incoming members of the Directing Board representing the IVS components.

4.2 IVS Correspondents

IVS Correspondents are individuals on a mailing list maintained by the Coordinating Center. They do not actively participate in IVS but express interest in receiving IVS publications, wish to participate in workshops or scientific meetings organized by IVS, or generally are interested in IVS activities. Ex officio correspondents are the following:
Version date: 20 October, 1998