Abstract's details
Using DORIS for modeling the Vertical Total Electron Content of the Earth's Ionosphere
CoAuthors
Event: 2014 IDS Workshop
Session: New DORIS missions, applications, and products
Presentation type: Type Oral
Contribution: not provided
Abstract:
The Earth's ionosphere is a dispersive medium for microwaves. As a consequence, most space-geodetic observation techniques can be utilized to extract information on ionospheric parameters, e.g. the Vertical Total Electron Content (VTEC). Nowadays, most geodetic VTEC models are solely based on observations from terrestrial permanent stations of the Global Navigation Satellite Systems (GNSS), especially of the Global Positioning System (GPS). However, by combining different techniques one can take advantage of their individual spatial and temporal data distributions as well as their different observation characteristics and sensitivities concerning ionospheric parameter estimation.
The "Doppler Orbitography and Radiopositioning Integrated by Satellite"(DORIS) system was originally developed for precise orbit determination of low Earth orbiting (LEO) satellites. Beyond that, it is highly qualified for modeling the distribution of electrons within the Earth's ionosphere. It measures with two frequencies in L-band with a relative ratio close to 5. Since the terrestrial ground beacons are distributed quite homogeneously and several LEOs are equipped with modern receivers, a good applicability for global VTEC modeling can be expected.
Recently, we included DORIS measurements in our ionosphere modeling process in order to test their capability and their potential to derive ionospheric parameters such as VTEC on a global scale. For this purpose, we compute DORIS VTEC values from the two-frequency measurements of Jason-2, Cryosat-2, HY-2A, and SARAL and include it in our ionosphere model approach where the unknown model parameters are estimated within an adjustment process. The weighting of the different observation groups is done by variance component estimation. By analyzing the estimated variance components we extract information on the quality of different DORIS missions for ionospheric modeling and on the consistency with other observation techniques.
The combination of DORIS VTEC with data from other space-geodetic measurement techniques improves the accuracy of global VTEC models significantly. If DORIS VTEC data is used to update IGS GIMs, an improvement of up to 12% can be achieved. The accuracy directly beneath the DORIS satellites' groundtracks ranges between 1.5 and 3.5 TECU assuming a precision of 2.5 TECU for altimeter-derived VTEC values which have been used for validation purposes.
The "Doppler Orbitography and Radiopositioning Integrated by Satellite"(DORIS) system was originally developed for precise orbit determination of low Earth orbiting (LEO) satellites. Beyond that, it is highly qualified for modeling the distribution of electrons within the Earth's ionosphere. It measures with two frequencies in L-band with a relative ratio close to 5. Since the terrestrial ground beacons are distributed quite homogeneously and several LEOs are equipped with modern receivers, a good applicability for global VTEC modeling can be expected.
Recently, we included DORIS measurements in our ionosphere modeling process in order to test their capability and their potential to derive ionospheric parameters such as VTEC on a global scale. For this purpose, we compute DORIS VTEC values from the two-frequency measurements of Jason-2, Cryosat-2, HY-2A, and SARAL and include it in our ionosphere model approach where the unknown model parameters are estimated within an adjustment process. The weighting of the different observation groups is done by variance component estimation. By analyzing the estimated variance components we extract information on the quality of different DORIS missions for ionospheric modeling and on the consistency with other observation techniques.
The combination of DORIS VTEC with data from other space-geodetic measurement techniques improves the accuracy of global VTEC models significantly. If DORIS VTEC data is used to update IGS GIMs, an improvement of up to 12% can be achieved. The accuracy directly beneath the DORIS satellites' groundtracks ranges between 1.5 and 3.5 TECU assuming a precision of 2.5 TECU for altimeter-derived VTEC values which have been used for validation purposes.