Analysis of the bias between TOPEX and GPS TEC determinations

BRUNINI CLAUDIO; AZPILICUETA FRANCISCO

Boston, Estados Unidos

Simposio; International Beacon Satellite Symposium; 2007

Boston College

Since TOPEX vertical TEC (vTEC) measurements became available, several validation studies against vTEC determinations from other sources have been carried out. Many of these studies have identified a vTEC constant bias between +2 and +5 TECU when compared to GPS and DORIS vTEC determinations (TOPEX greater than the others). Based on La Plata Ionospheric Model, global vTEC maps have been computed on a day-to-day basis for the years 1998 and 1999, and comparisons against TOPEX vTEC determinations have shown a constant bias ranging from +3 to +4 TECU. The available documentation relative to the computation of TOPEX products reports that a correction of +15mm is applied to the final range computed. This correction is applied empirically, i.e. without any analysis of the source and without any study of the implications of it on TOPEX vTEC determinations. In the present contribution, we show that with slight changes on the constant corrections used in TOPEX processing algorithm that are applied to TOPEX measurements on each frequency, TOPEX vTEC bias disappear and the +15 mm range correction is no longer needed.