S.: IGS Products for the Ionosphere

In June 1992 the International GPS Service for Geodynamics (IGS) started with the routine provision of precise GPS orbits and earth orientation parameters. In the meantime other products were included into the product palette: rapid orbits, predicted orbits, GPS satellite clock information, station coordi-nates and velocities (SINEX), and station-specific tropospheric zenith delays. For long time the IGS community is well aware of the fact that the world-wide IGS network offers a unique opportunity to extract ionospheric information on a global scale. At the IGS workshop held in Silver Spring in March 1996, a first sub-session was dedicated to the ionosphere. Main subject of this ionosphere sub-session was an intercomparison of ionosphere products provided by several Analysis Centers in order to get an idea of the accuracies that can be achieved. In addition it was identified for the first time, which Analysis Centers indicated their willingness to contribute to an IGS ionosphere product. Since 1996 considerable progress in ionosphere modeling has been achieved at the different Analysis Centers, and today most of them are able, or in a position very close to be able, to provide ionosphere information on a routine basis. An official format for the exchange of ionosphere maps, called IONEX, has been worked out and approved. It will be the main task of the 1998 IGS Workshop to prepare the start of a coordinated routine processing and combination of future IGS ionosphere prod-ucts.