Analysis of the bias between TOPEX and GPS vTEC determinations

AZPILICUETA F.; BRUNINI C.; GENDE M.

Cairns

Congreso; Dynamic Planet. IAG/IAPSO/IABO Joint Assembly; 2005

International Association of Geodesy

Since the availability of TOPEX vertical TEC (vTEC) measurements several validation studies against vTEC determinations from other sourceshave been performed. Many of these studies have identified a vTEC constant bias between +3 and +5 TECu (TOPEX greater than the others)when they are compared to GPS and DORIS vTEC determinations.Based on La Plata Ionospheric Model, global vTEC maps have been computed on a day to day basis for years 1998 and 1999, and comparedto TOPEX vTEC determinations. This comparison confirms a constant bias ranging from +3 to +3.6 TECU.The available documentation provided by TOPEX processing centers relative to the computation of geophysical data records, reports that aconstant correction of +15 mm is applied to the final range computed by the TOPEX altimeter for the analyzed period. This correction isempirically applied to eliminate the discrepancy between TOPEX and Poseidon range measurements and to solve sea level height calibrationproblems of TOPEX altimeter.In the present contribution we propose that the TOPEX-GPS vTEC bias and the TOPEX sea level height bias could be both explained by amiss-calibration on the range corrections applied to TOPEX range determinations on both frequencies.