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Annex: The ICSU Federation of Astronomical and Geophysical
Data Analysis Services

The earliest scientific measurements were probably of the movements of the sun through the heavens. When wise men among the ancients developed scientific theories to fit the observed facts, they did so to satisfy the practical human demands of adjusting to the seasons. Like today's scientists, they must have understood the basic experimental requirement: good science needs good data. Studies of the Earth, the solar system and the universe demand data of the highest quality, measured systematically over as long a period as possible.

Although such observations have been made since time immemorial, few records were kept in a systematic way to allow detailed analyses and the identification of trends and changes. The Federation of Astronomical and Geophysical Analysis Services (FAGS), formed in 1956, is an Interdisciplinary ICSU Body. FAGS includes ten individual Services each operating under the authority of one or more of the sponsoring ICSU Unions: IAU, IUGG and URSI. Each Service Director is an acknowledged international authority on the phenomena for which the Service is responsible; each Director is charged not only with receiving data from a world wide network of co-operating agencies, but also for quality control, dissemination of data and advice to interested scientists, and above all for applying his expertise to the scientific analysis and interpretation of the integrated sets of observations.

Scientific interest in these analyses continues to grow. For example, recent studies of the variations in the rate of rotation of the Earth are important in relation to meteorological changes, glacier distribution in polar regions, geomagnetic activity and space navigation. The long-term changes are of special interest, for example in anticipating the effects of climate trends on the global economy, the possibility that slow tectonic movements and tides may play a role in triggering Earthquakes, and the coastal impacts of secular changes in sea levels.

FAGS Services give special attention to questions of instrument calibration, resolution and stability. Reliable scientific analyses of small but important long-term geophysical trends is only possible if the methods of making the measurements over decades and centuries have been carefully controlled. No new measuring procedure can be introduced without careful comparison and checks for compatibility with the older methods. Here the advice and experience of the Service Directors is invaluable as guidance for the network of individual measuring systems which operate at a national level.

Each Service works independently, under the general auspices of FAGS, towards the common goal of long-term scientific excellence in data analysis and interpretation of astronomical and geophysical variability. The sponsoring Unions appoint Advisory Boards with strong international membership to guide and assist each Director to achieve these goals.

Although the central co-ordination of FAGS began under ICSU as recently as 1956, many of the Services have a longer history. Most maintain data which has been collected over decades, and in some cases, centuries. It is appropriate to consider the special activities of each Service in turn.

International Earth Rotation Service. (established in 1895) Paris

maintains the terrestrial reference system for both positions and velocities; it also maintains an extragalactic celestial reference system and determines the Earth orientation parameters which connect these systems; it organises the observational activities necessary to collect the appropriate data. The advent of satellite geodetic measurements such as Very Long Baseline radio Interferometry, Lunar Laser Ranging, the Global Positioning System, and Satellite Laser Ranging, has revolutionised the accuracy of the studies: crustal movements as small as 2 to 5 mm per year are detectable, and changes in the length of the day are monitored to within 0.0002 seconds. The various IERS results contribute in many ways to space research, astronomy and geophysics. For example, data on Earth's rotation are interpreted in terms of mantle elasticity, structure and properties of the core-mantle boundary, rheology of the core, underground waters, ocean circulation, atmospheric winds and mass distribution.

Quarterly Bulletin on Solar Activity (1928) Japan

publishes a Bulletin, a record of solar activity which is as final and complete as possible, for studying short and long-term activities of the sun. These activities include sunspots, synoptic charts of solar magnetic fields, chromospheric eruptions, intensity of the solar wind, and solar radio emissions. More than 70 observatories and institutes contribute observations to these syntheses.

International Service for Geomagnetic Indices (1932) St Maur, France

collects and publishes data disturbance variations of the geomagnetic field. Disturbances include sudden commencement of magnetic storms, solar flare effects, and pulsation disturbances. Variations in the intensity of the Earth's magnetic field are related to the level of solar activity, and the amount of energy coming from the sun into the Earth's environment.

Permanent Service for Mean Sea Level (1933) Merseyside, UK

collects and analyses monthly mean sea level data from a global network of tide gauges. These gauges are operated by a wide range of national authorities: hydrographers, surveyors, oceanographic institutes, and individual university departments. PSMSL works to improve the quality of the measurements, and the range of global coverage. There is a shortage of reliable long-term sea level observations in the Antarctic, and from ocean islands. The latter are important to get an even coverage of the measurements; to increase the data flow, PSMSL has worked with the Intergovernmental Commission of UNESCO to develop GLOSS, an Intergovernmental system for measuring sea levels to common high standards. Altimetry has given a new momentum to these analyses, and in future the emphasis will be on developing integrated products for sea level based on both coastal and satellite measurements. In recent years the prospects of global warming, and possible enhanced rates of sea level rise have made the demands for PSMSL analyses more urgent. Present rates of sea level rise of 0.15 m per century may increase, but there is no evidence for this yet.

Bureau Gravimétrique International (1951) Toulouse, France

collects on a world wide basis, all gravity measurements and pertinent information about the gravity field of the Earth; it compiles and stores the information on a computerised data base in order to redistribute them to a large variety of scientific users. Other data such as mean values of gravity anomalies, geoid heights, topographic heights, and satellite altimetry derived geoid heights are also collected and distribute to scientists world-wide. The BGI also records absolute measurements of gravitational acceleration. One of the applications in which BGI assists is the preparation of geoids for cartographic and hydrographic applications.

International Centre for Earth Tides (1960) Brussels

Ocean tides are easily observed by the casual coastal visitor, but the gravitational attractions of the moon and sun are also felt by the solid Earth. The forces and the Earth's responses to these can be calculated and measured to great accuracy. These Earth responses relate to the elasticity of the mantle and to the properties of the liquid core. Movement of water due to ocean tides also affects the crustal deformations observed by sensitive gravity metres, tilt metres and strain gauges. When known, global effects are removed from the records, and the residuals are analysed in terms of local phenomena and tectonic features.

International Ursigram and World Day Service (1962) Chatswood, Australia

describes itself as "The World Space Weather Warning Service". It operates through a network of ten Regional Warning Centres, which have responsibility for collecting data in their geographic area and distributing it to users through the other centres. The wide distribution of these centres is typical of many of the FAGS Services: Paris, Prague, Warsaw, Moscow, New Delhi, China, Tokyo, Sydney Australia, Boulder USA and Ottawa. Warnings of disturbances in the solar terrestrial environment are used by radio communicators, surveyors using geophysical techniques, power line and pipe line authorities, operators of satellites, and a host of scientific users. IUWDS also encourages co-ordinated observations by preparing the International Geophysical Calendar each year; this lists a series of `world days' which scientists may use to carry out synchronised experiments.

World Glacier Monitoring Service (1967) Zurich

Increased interest in possible global warming has focused on trends in the extent of glaciers; maps of fluctuations are published at 5-year intervals. A century of systematic observations clearly reveal a general shrinkage of mountain glaciers on a global scale, which provides one of the most reliable pieces of evidence for a secular warming trend. Glacier inventory information provides the basis for identifying global trends, and for isolating locally anomalous behaviour; but interpretation is not straight forward, and standard procedures for monitoring glacier length and volume must be applied.

Sunspot Index Data Centre (1985) Brussels

Since 1981 the SIDC has collected data from some 40 co-operating centres to calculate a provisional sunspot number, but the records go back as far as 1700. Recently the Service has begun separate analyses of activity in the two solar hemispheres. On top of the well known 11 year periodicity, there are many shorter and longer-term fluctuations. Apart from strong scientific interest, users include space-centres and telecommunication systems. SIDC issues 12-month forecasts, with necessary cautions. Until 1997 the level of sun spot activity will generally decrease through the 11-year cycle.

Centre de Données Stellaires (1985) Strasbourg

is the world reference data base for the identification of astronomical objects. It collects all of the useful data concerning these objects from observatories around the world, upgrades these information by critical evaluation and comparisons, and distributes the results for further research. CDS has also had a major part to play in most of the major astronomical space missions, by identifying observed sources, and by helping to solve problems of data archiving and access.

There is no typical FAGS Service, but as the above summary shows, there is a general theme: of attention to co-ordinated global observing systems of the highest quality; data assimilation; analysis and interpretation of these data using the best scientific expertise; and a commitment to make these results available for other scientists and for a wide range of other practical applications.

ICSU and the Scientific Unions provide a small sum of money to assist the services in their central activities, but the main support comes in each case from the national authorities which undertake these responsibilities for the benefits of international science. The Council of FAGS ensures that standards are maintained, and that where possible, links among the Services are developed. Joint meetings of the Services Directors and the FAGS Council are held every four years, to exchange ideas and experience, and occasional cross-Service scientific meetings are organised. In December 1993 the Permanent Service for Mean Sea Level is celebrating 60 years of operation at a meeting to which it has invited Directors of several of the other FAGS Services.

The driving force and vision which established a coordinated system of astronomical and geophysical observations and analysis within ICSU came from the scientists, who demanded data of the highest quality to enhance our understanding of the Earth on which we live, and of the solar and stellar systems which surround us. But the final acknowledgement must go to the generations of anonymous observers without whose patient and exact application of their measuring skills, none of this would have been possible.

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