International Earth Rotation and Reference Systems Service

International Earth Rotation and Reference Systems Service
Name	International Earth Rotation and Reference Systems Service
Founded	0 1987
Headquarters	Paris Observatory
Type	International organization
Key people	Christian Bizouard (Director)
Website	https://www.iers.org

International Earth Rotation and Reference Systems Service. It is the global authority responsible for defining and maintaining the fundamental reference frames and parameters that describe the rotation of the Earth in space. The service provides the data and standards essential for precise geodesy, space navigation, and astronomy. Its work underpins modern systems like the Global Positioning System and supports research into geophysics and climate change.

Overview and mission

The primary mission is to establish and disseminate the International Terrestrial Reference System and the International Celestial Reference System, which are the foundational coordinate systems for measuring positions on Earth and in the sky. It determines crucial parameters such as Universal Time and the Earth orientation parameters, which describe the irregularities in our planet's rotation. This work is vital for the accurate operation of satellite navigation constellations, including GLONASS and Galileo, and for tracking missions by agencies like NASA and the European Space Agency. The service also monitors phenomena like polar motion and the length of day, providing essential data for studying the Earth's core and angular momentum exchange within the Earth system.

Organizational structure

The service is structured as a federation of several technical components, each hosted by leading institutions worldwide. The Directing Board, composed of representatives from member organizations like the International Astronomical Union and the International Union of Geodesy and Geophysics, provides overall governance. Key operational centers include the Central Bureau, historically located at the Paris Observatory in France, and specialized Product Centers such as the Rapid Service/Prediction Center at the United States Naval Observatory. Other vital units are the Global Geophysical Fluids Center, analyzing mass redistribution, and the Combination Research Center, which synthesizes data from techniques like Very Long Baseline Interferometry and Doppler Orbitography.

Products and services

Its primary products are the highly precise Earth orientation parameters, which are published through regular bulletins and made available to users in near-real time. These include data on UT1-UTC and celestial pole offsets, critical for transforming coordinates between the terrestrial and celestial frames. The service also maintains and provides access to the International Terrestrial Reference Frame, a precise realization of the terrestrial system, and the International Celestial Reference Frame, based on positions of distant quasars. These products are indispensable for the orbit determination of satellites, deep-space missions conducted by JAXA, and fundamental astronomy at observatories like the Very Large Telescope.

Standards and conventions

The service is responsible for defining and promoting the use of internationally accepted standards and conventions in Earth rotation and reference systems. This includes maintaining the definitions and realizations of key systems like the International Terrestrial Reference System and the Conventional International Origin. It works in close concert with other standards bodies, notably the International Union of Geodesy and Geophysics and the Committee on Earth Observation Satellites, to ensure consistency. These conventions are formally adopted by resolutions of the International Astronomical Union and are used in major projects like the Global Geodetic Observing System.

History and development

The service was established in 1987 by the International Astronomical Union and the International Union of Geodesy and Geophysics, merging the earlier International Polar Motion Service and the Bureau International de l'Heure. This consolidation responded to the growing need for a unified service capable of handling new space-geodetic techniques such as Lunar Laser Ranging and Satellite Laser Ranging. Over the decades, its role expanded with the advent of the Global Positioning System, requiring ever more precise reference frames. Milestones include the adoption of the J2000.0 celestial frame and the successive iterations of the International Terrestrial Reference Frame, each improving accuracy through contributions from global networks like the International GNSS Service.

Collaborating organizations

The service functions through extensive collaboration with a global network of scientific institutions and observation services. Key partners include the International VLBI Service for Geodesy and Astrometry, the International Laser Ranging Service, and the International DORIS Service, which provide the raw measurement data. It also works closely with the International GNSS Service and the International Gravity Field Service. Funding and scientific support come from member nations' agencies, such as the National Geospatial-Intelligence Agency and the Bundesamt für Kartographie und Geodäsie, and through partnerships with entities like the Jet Propulsion Laboratory and the Institut Géographique National.

Category:International scientific organizations Category:Geodesy Category:Astronomical organizations