Validation of Jason-1 Nadir Ionosphere TEC Using GEONET

The Jason-1 dual-frequency nadir ionosphere Total Electron Content (TEC) for 10-day cycles 1–67 is validated using absolute TEC measured by Japan's GPS Earth Observation Network (GEONET), or the GEONET Regional Ionosphere Map (RIM). The bias estimates (Jason–RIM) are small and statistically insignificant: 1.62 ± 9 TECu (TEC unit or 1016 electrons/m2, 1 TECu = 2.2 mm delay at Ku-band) and 0.73 ± 0.05 TECu, using the along-track difference and Gaussian distribution method, respectively. The bias estimates are –3.05 ± 10.44 TECu during daytime passes, and 0.02 ± 8.05 TECu during nighttime passes, respectively. When global Jason-1 TEC is compared with the Global Ionosphere Map (GIM) from the Center for Orbit Determination in Europe (or CODE) TEC, the bias (Jason–GIM) estimate is 0.68 ± 1.00 TECu, indicating Jason-1 ionosphere delay at Ku-band is longer than GIM by 3.1 mm, which is at present statistically insignificant. Significant zonal distributions of biases are found when the differences are projected into a sun-fixed geomagnetic reference frame. The observed biases range from –7 TECu (GIM larger by 15.4 mm) in the equatorial region, to +2 TECu in the Arctic region, and to +7 TECu in the Antarctica region, indicating significant geographical variations. This phenomena is primarily attributed to the uneven and poorly distributed global GPS stations particularly over ocean and near polar regions. Finally, when the Jason-1 and TOPEX/Poseidon (T/P) TECs were compared during Jason-1 cycles 1–67 (where cycles 1–21 represent the formation flight with T/P, cycles 22–67 represent the interleave orbits), the estimated bias is 1.42 ± 0.04 TECu. It is concluded that the offset between Jason/TOPEX and GPS (RIM or GIM) TECs is < 4 mm at Ku-band, which at present is negligible.

[1]  M. Tulder.  Chapter 1 , 2006, European Spine Journal.

[2]  Hermann Lühr,et al.  The diamagnetic effect of the equatorial Appleton anomaly: Its characteristics and impact on geomagnetic field modeling , 2003 .

[3]  L. A. Scidá,et al.  F2 region maximum electron density height predictions for South American latitudes , 2003 .

[4]  Bruce J. Haines,et al.  The Jason-1 Mission Special Issue: Jason-1 Calibration/Validation , 2003 .

[5]  Chung-Yen Kuo,et al.  Calibration of JASON-1 Altimeter over Lake Erie Special Issue: Jason-1 Calibration/Validation , 2003 .

[6]  Koji Matsumoto,et al.  A degree 180 spherical harmonic model for the lunar topography , 2003 .

[7]  Koji Matsumoto,et al.  Regional ionosphere map over Japanese Islands , 2002 .

[8]  G. Beutler,et al.  Evaluation of IRI95 ionosphere model for radar altimeter applications , 2002 .

[9]  Takuya Tsugawa,et al.  A new technique for mapping of total electron content using GPS network in Japan , 2002 .

[10]  Bodo W. Reinisch,et al.  International Reference Ionosphere 2000 , 2001 .

[11]  John C. Ries,et al.  Chapter 1 Satellite Altimetry , 2001 .

[12]  L. A. Leonovich,et al.  The use of the international GPS network as the global detector (GLOBDET) simultaneously observing sudden ionospheric disturbances , 2000 .

[13]  S. Schaer.  Mapping and predicting the Earth's ionosphere using the Global Positioning System. , 1999 .

[14]  Shoichiro Fukao,et al.  High resolution mapping of TEC perturbations with the GSI GPS Network over Japan , 1998 .

[15]  Anthony J. Mannucci,et al.  A global mapping technique for GPS‐derived ionospheric total electron content measurements , 1998 .

[16]  Xiaoqing Pi,et al.  Global ionosphere perturbations monitored by the Worldwide GPS Network , 1996 .

[17]  Leos Mervart,et al.  Global and regional ionosphere models using the GPS double difference phase observable , 1996 .

[18]  David A. Imel,et al.  Evaluation of the TOPEX/POSEIDON dual-frequency ionosphere correction , 1994 .

[19]  E. J. Christensen,et al.  TOPEX/POSEIDON mission overview , 1994 .

[20]  B. Wilson,et al.  A New Method for Monitoring the Earth's Ionospheric Total Electron Content Using the GPS Global Network , 1993 .

[21]  J. Klobuchar.  Ionospheric Time-Delay Algorithm for Single-Frequency GPS Users , 1987, IEEE Transactions on Aerospace and Electronic Systems.

[22]  Dieter Bilitza,et al.  International reference ionosphere , 1978 .

[23]  Rodney B. Bent,et al.  Documentation and Description of the Bent Ionospheric Model , 1973 .