GPS-based ionospheric corrections for single frequency radar altimetry

The global ionospheric total electron content maps (GIMs) provide integrate d electron densities between the ground and the GPS satellite altitude (20, 200 km). Satellite altimeter ionospheric delay corrections require integrat ed electron densities between the ground and altimeter satellite altitude. In the case of the Geosat Follow-On (GFO) spacecraft, flying at 800 km. we estimated that using GIM TEC data alone, up to a 2 cm path delay can be int roduced into the GFO measurements for high solar activity period by not tak ing into account the electron content above this altitude. Furthermore, the GIMs can have errors of 20-30 TECU in low latitudes for high solar activit y in areas where there is little GPS data (such as over the oceans). In thi s paper, we describe the results of ingesting GIM TEC data into the Interna tional Reference Ionosphere model (IRI-95) to mitigate these two effects. ( C) 2000 Elsevier Science Ltd. All rights reserved.