1. Bosch & Shum -- Need for an IAS? GE8, Paris, 10/20031 A Call to Study Rationale, Feasibility and Scope of an International Altimeter Service (IAS) Do we need an International Altimeter Service? W. Bosch 1) and C.K. Shum 2) 1) Deutsches Geodätisches Forschungsinstitut (DGFI), München email: bosch@dgfi.badw.de 2) Laboratory for Space Geodesy and Remote Sensing Research, The Ohio State University

2. Bosch & Shum -- Need for an IAS? GE8, Paris, 10/20032 Altimetry has demonstrated an interdisciplinary application potential (relevant to sea level, oceanography, geodesy, global change..) will have to be a core element of global Earth observing systems (GLOSS, GOOS, GTOS, GCOS, IGGOS,....) is requested to provide long and accurate time series with harmonized corrections and consolidated georeference requires cross-calibration between contemporary and follow- on missions as well as with new technologies (LIDAR, laser -, wide swath altimetry,...)

3. Bosch & Shum -- Need for an IAS? GE8, Paris, 10/20033 Deficiencies providing additional rationales for an IAS Users do not have a single point-of-contact! There are many (!!) different formats for altimeter data Increasing data volume and complexity Orbits and geophysical corrections are not always up-to-date Reference system relationship and long-term stability of altimetry not sufficiently solved

4. Bosch & Shum -- Need for an IAS? GE8, Paris, 10/20034 Altimeter users are already served! AVISO (CLS) harmonized T/P and ERS1/2, corrected sea surface heights and sea level anomalies NASA Pathfinder harmonized T/P, ERS-1/2 and Geosat, „stacked“ data files for analysis of sea level variations. PO.DAAC (JPL) provides the T/P data, a dedicated SLA product, enhanced ERS-1 data, keeps Geos-3 and Seasat Delft (DEOS) precise orbits for ERS-1/2 RADS (DEOS, Delft) on-line archive with improved orbits and up-to-date geophysical, cross-calibration/validation of Envisat/ERS, Jason/T/P, GFO ADS Central (GFZ, Potsdam) nearly as complete as RADS; updates for media corrections; user defined data extracts.

5. Bosch & Shum -- Need for an IAS? GE8, Paris, 10/20035 General IAS Objectives Serve altimeter users! –there are both, operational and scientific users –compile user requirements (see already available key documents) Integrate already existing value-adding entities, asked to –contribute through the provision of data and products –become actively involved and help to develope and configure IAS

6. Bosch & Shum -- Need for an IAS? GE8, Paris, 10/20036 IAS Working Group Is looking for integration of & support from –Space agencies & administrations (CNES, ESA, NASA, NOAA,...) –Scientific Organisations (IAG, IAPSO, IOC,... –Data/product centres (PO.DAAC, SSALTO/DUACS, DEOS/RADS,... –Observation systems (GLOSS, GOOS, GTOS, GCOS, IGGOS,... –Already existing services (IGS, PSMSL, IERS,...) Splinter Meeting on Thursday, 10 October, 8am