President: Urs Hugentobler (Germany)
Director of the Central Bureau: Ruth Neilan (USA)
A proof of concept for the International Global Positioning System (GPS) Service for Geodynamics (IGS) was conducted with a three-month campaign during June through September 1992, and continued until December 1993 as a Pilot-Service until the establishment of the IGS as a service of the International Association of Geodesy (IAG). The IGS formally began on 1 January 1994. IGS is a member of the Federation of Astronomical and Geophysical Data Analysis Services (FAGS) and it operates in close cooperation with the International Earth Rotation and Reference Systems Service (IERS). Due to the expansion of IGS objectives, the name of the service was changed to International GPS Service (IGS) on 1 January 1999. Following further expansion of IGS, integrating data from the Russian GLONASS system and planning for the deployment of the European Galileo system, the name was changed to ‘International Global Navigation Satellite System (GNSS) Service’ on 14 March 2005. The organization retains the acronym ‘IGS’.
The International GNSS Service is committed to providing the highest quality data and products as the standard for Global Navigation Satellite Systems (GNSS) in support of Earth science research, multidisciplinary applications, and education. These activities endeavour to advance scientific understanding of the Earth system components and their interactions, as well as to facilitate other applications benefiting society. The Service also develops the necessary standards and specifications and encourages international adherence to its conventions.
The IGS strives to:
- Provide the highest quality, reliable GNSS data and products, openly and readily available to all.
- Promote universal acceptance of IGS products, standards and conventions.
- Continuously innovate by attracting leading-edge expertise and pursuing challenging projects and ideas.
- Seek and pursue new growth opportunities while responding to changing user needs.
- Sustain and nurture the IGS culture of collegiality, openness, inclusiveness, and cooperation.
- Maintain a voluntary organization with effective leadership, governance, and management.
The IGS collects, archives and distributes GNSS observational data sets of sufficient accuracy to satisfy the objectives of a wide range of applications and experimentation. These data sets are used by the IGS to generate the following data products:
- High accuracy GPS satellite ephemerides and related information
- Earth rotation parameters
- Coordinates and velocities of the IGS tracking stations
- GPS satellite and tracking station clock information, timescale products
- Ionospheric information
- Tropospheric information
The accuracies of these products are sufficient to support satellite orbit determination
- Ionosphere monitoring
- Climatological scientific objectives including:
- Realization of global accessibility to, and the improvement of, the International Terrestrial Reference Frame (ITRF)
- Monitoring deformation of the solid Earth
- Monitoring earth rotation
- Monitoring variations in the hydrosphere (sea level, ice sheets, etc.)
- Scientific research, eventually weather prediction models
- Time and frequency transfer
The IGS accomplishes its mission through the following components:
- Networks of tracking stations
- Data Centers (DCs)
- Analysis and Associate Analysis Centers (AACs)
- Analysis Center Coordinator (ACC)
- Working Groups, Pilot Projects, Pilot Services (WG, PP, PS)
- Coordinators for special products or components: e.g. Reference Frame, Network, Timing
- Central Bureau (CB)
- Governing Board (GB)
Networks of Tracking Stations
IGS Stations provide continuous tracking using high-accuracy receivers and have data transmission facilities allowing for rapid (minimally daily) data transmission to the data centres (see below). The stations must meet physical and operational requirements as defined in the ‘IGS Site Guidelines’ document available from the Central Bureau.
The ensemble of the IGS stations is the IGS network.
IGS data centres fall into three categories: Operational, Regional, and Global Data Centers. Each has varied duties which must be carried out continually and with a minimum of delay or downtime, although the multiplicity of DCs provides a measure of redundancy. The description and responsibilities of each type of DC are detailed in the separate policy document ‘IGS Data Centers Charter’ and include duties such as collecting data from GPS tracking stations and ancillary equipment, data validation, permanent archival, providing online availability, and transmittal to and equalization with other DCs. The set of DCs provides for open access to IGS data and products by IGS participants and all external users. DCs are approved by the IGS GB following demonstration of qualifications and commitment.
The analysis centres fall into two categories: Analysis Centers (ACs) and Associate Analysis Centers (AACs). The Analysis Centers receive and process tracking data from one or more data centres for the purpose of producing IGS products. The Analysis Centers are committed to submit products for combination into IGS products, without interruption, using designated standards and conventions, and within a specified time delay to meet IGS requirements.
The Analysis Centers generally provide the core products of ephemerides, Earth rotation parameters, station coordinates, and clock information, as well as other recommended products, such as rapid, predicted or real-time orbit and Earth rotation solutions.
Associate Analysis Centers produce specialized products recognized by the Governing Board, e.g., ionospheric information, tropospheric parameters, or station coordinates and velocities for a global or regional sub-network.
The ‘Charter for Analysis Centers and Associate Analysis Centers’ is a policy statement of the Governing Board and is available from the Central Bureau.
Analysis Center Coordinator
The Analysis Center Coordinator (ACC, also referred to as the Analysis Coordinator) assists the Analysis Centers. The Analysis Center Coordinator monitors the activities of the Analysis Centers to ensure that the IGS objectives are carried out.
Specific expectations include quality control, performance evaluation, and continued development of appropriate analysis standards. The Analysis Coordinator is also responsible for the appropriate combination of the Analysis Centers’ products into a single set of orbit and clock products, which are official IGS products delivered to the Global Data Centers.
The Analysis Center Coordinator is a voting member of the IGS Governing Board (see below) and interacts regularly with the Central Bureau and the IERS. The Analysis Coordinator (or designee as approved by the Governing Board) is one of the two IGS representatives to the IERS Directing Board.
Generally the responsibilities for the Analysis Coordinator shall rotate among the Analysis Centers with appointments and terms specified by the Governing Board.
Working Groups, Pilot Projects, and Product Coordinators
A Working Group works on a particular topic related to the IGS mission according to goals and schedule specified in the Working Group’s charter. A Pilot Project aims at the development of particular new IGS product(s) or service(s) relying on the IGS infrastructure. A Product Coordinator is responsible for a specialized product related to the IGS missions and components, as specified in its charter. Each Product Coordinator is supported by a Working Group, whose members take responsibility for providing routine contributions to a combined product, and/or make expertise available to the Working Group.
The Governing Board establishes and terminates Working Groups and Pilot Projects, and appoints the Working Group Chairs and Product Coordinators. A minimum initial commitment for any Product Coordinator is four years. The ‘IGS Policy to Establish Working Groups, Projects, and Product Coordinators’ is a policy statement of the Governing Board and is available from the Central Bureau.
Chairs of Working Groups and Pilot Projects are nonvoting members of the IGS Governing Board (see below). The Coordinators of the fundamental products shall be voting members of the Board (Analysis Coordinator, Reference Frame Coordinator, Timing Coordinator). Coordinators of derived products are non-voting members.
In the case of products requiring significant joint expertise, the GB may approve GB membership of a representative of a partner organization, in order to ensure appropriate representation and communication. Such a representative is designated by the partner organization and is a non-voting member of the GB. It will normally be expected that the GB will in turn be invited to appoint an IGS representative to the Directing Board, or equivalent body, of the partner organization.
The Central Bureau (CB) is the executive arm of the IGS Governing Board, responsible for the general management, coordination and day-to-day operations of the IGS consistent with the directives, policies and priorities set by the Governing Board.
The principal roles of the Governing Board (GB) are to set policy and to exercise broad oversight of all IGS functions and components. It also controls general activities of the Service, including restructuring, that would be appropriate to maintain efficiency and reliability, while taking full advantage of the advances in technology and theory.
The Executive Committee (EC) of the IGS Governing Board is established as a committee that has specific responsibilities allowing it to act on behalf of the GB for the following purposes: 1) to codify and organize issues that are brought to the Board for action, 2) to act for the Board when a quorum of the Board is not present, 3) to act for the Board when a full Board meeting is not possible or necessary. The EC is responsible for exercising the powers of GB in the management of the business and affairs only to the extent set forth in the Terms of Reference.
IGS Associate Members
Associate Members are persons representing organizations that participate in any of the IGS components. The membership is balanced with respect to IGS components, organizational representation and geography, and is meant to represent institutions which contribute significantly to the IGS on a continuous basis. Each organization that meets the above criteria shall have a minimum of one and not more than ten Associate Members. The Central Bureau maintains the list of Associate Members, which is revised annually and is subject to the approval of the Governing Board.
Associate Members elect the six members of the GB representing Analysis Centers, Data Centers and Networks (except for those nominated by the CB). The list of Associate Members eligible to vote in elections must be approved by the GB at least three months prior to the election process. Current and former GB members are considered Associate Members.