3D electron density specification to support LEO and MEO satellite applications

The TaD three-dimensional (3D) electron density (Ne) specification model is compared with in situ measured Ne by the Instrument Sonde Langmuir (ISL) onboard DEMETER satellite. For this purpose, over 2000 parts of satellite orbits over the European region in the years 2009-2011 were selected. For each measured Ne value, a corresponding value was calculated with the TaD 3D model, using maps of foF2 and hmF2 from ionosondes and maps of TEC values from CODE software. To compare modelled and measured Ne, the relative to the model deviation between the two quantities was calculated. The comparisons exceeded the total number of 180,000. The main result shows that the modelled Ne extracted by the TaD profiles that have been calculated through adjustment with the TEC CODE parameters, exhibit significant deviations from the measured Ne at the satellite orbit height. Histograms of the relative deviations relNe show an average offset of 50-60%, while the standard deviation is around 30%. Separate analysis was performed to compare the modelled Ne over 11 ionosonde stations with the measured Ne by the satellite over the ionosonde locations and thus to eliminate the error inferred from the mapping procedure. Here the TaD profiles were adjusted with both the TEC CODE parameters and with TEC values extracted with the single GNSS station solution software with data from GNSS receivers co-located with the ionosondes. In the latter case, the lower TEC values compared to those of TEC CODE yield lower modelled Ne which resulted to smaller deviations with the satellite data. The present study reveals the low consistency between different measurements involved in modeled reconstruction. The comparison presented here shows the importance of assessing the inconsistency between different measurements being assimilated or ingested in the 3D Ne models. Probable inconsistency of different data can create a wrong base for further geophysical studies.