The International GPS Service (IGS) Ionosphere Working Group

This article is presented on behalf of the International GPS Service (IGS) Ionosphere Working Group (Iono_WG) and describes the Working Group's activities. Detailed information about the IGS in general can be found on the IGS Central Bureau Web page: http://igscb.jpl.nasa.gov. The Iono_WG commenced working in June 1998. The working group's main task is the routine provision of ionosphere Total Electron Content (TEC) maps with a 2-hours time resolution and of daily sets of Global Positioning System (GPS) satellite and receiver hardware differential code bias (DCB) values. The computation of these TEC maps and DCB sets is based on the routine evaluation of GPS dual-frequency tracking data recorded with the global IGS tracking network. Currently five so called IGS Ionosphere Associate Analysis Centers (IAACs) produce with their models and software routinely TEC maps and DCB sets and provide their ionosphere products to IGS Ionosphere Associate Combination Center (IACC) at ESA/ESOC. Once per week the IACC compares then these ionosphere products with a dedicated comparison algorithm. This algorithm is currently being upgraded to be able to compute a combined IGS ionosphere product from the individual IAACs inputs (at the publication date of this paper the upgrade was completed). This new product shall soon be made available to external users through the Crustal Dynamics Data Information Center (CDDIS), NASA Goddard Space Flight Center, Greenbelt, NM, U.S.A. Beyond the routine provision of ionosphere products, the Iono_WG intends to support the ionosphere community also with other activities, e.g. by using the IGS global tracking network and capabilities to run high-rate data campaigns during events of special relevance for the ionosphere. In such campaigns, dual frequency GPS receivers record, depending on a receiver's capability, with 1 second or with 3 second sampling rate. A first such campaign was organized during the total solar eclipse on 11 August 1999, a second campaign was run recently under the name "HIRAC/SolarMax" over 7 days from 23 - 29 April 2001. In the medium- and long-term, the working group intends to develop more sophisticated algorithms for deducing mappings of ionospheric parameters from GPS measurements and to realize near-real-time availability of IGS ionosphere products. It is the intent of this paper to give an overview over the Iono_WG activities and to point out the importance of GPS for routine ionosphere monitoring. (C) 2003 COSPAR. Published by Elsevier Science Ltd. All rights reserved.