# Galileo Single Point Positioning Assessment Including FOC Satellites in Eccentric Orbits
## 4 Discussion  
We analyzed and assessed how the inclusion of the Milena (E14) and Doresa (E18) satellites impacts the position domain accuracy. In order to achieve this goal, we used a dataset of 20 days of 1-Hz observations collected by a static receiver placed in the YEL2 IGS station. Two different scenarios were considered: the first excluded the measurements coming from the Milena (E14) and Doresa (E18) satellites, while the second one included these observations. First, the results related to the analysis of the signal-to-noise ratio are discussed, then those relative to system availability and DOP analysis and finally those relative to positioning accuracy achieved by using both broadcast and precise ephemeris. In the following are reported the main conclusion based on the experiments conducted.  
* The evolution of the C/N\({}_{0}\) of the E14 and E18 satellites was similar to that of the other FOC satellites in the YEL2 site. As expected, the Milena (E14) and Doresa (E18) satellites showed a higher C/N\({}_{0}\) with respect to the other FOC satellites, confirming results shown in previous studies. This behavior was due to the lower altitude of Milena (E14) and Doresa (E18) caused by their elliptical orbit. The comparison between the carrier-to-noise density ratio (C/N\({}_{0}\)) at the different frequencies of the Milena (E14) and Doresa (E18) satellites revealed that for both satellites, the E5 signal had a C/N\({}_{0}\) higher than the others. Starting from 40 degrees, it can be seen that the E5b signal had a C/N\({}_{0}\) higher than the E5a signal and this higher than E1. For elevation angles lower than 30 degrees, the E1 signal showed a carrier-to-noise density ratio higher than E5b.
* As expected, the inclusion of the two satellites improved:
* the system availability, varying it from 94.1-97.94%.
* the GDOP, PDOP, HDOP, and VDOP parameters in each DOY analyzed;
* the percentages of achieved positioning solutions by about 5% regardless of the frequency used.
* When the broadcast ephemerides were used, nevertheless, the above results of the inclusion of the satellites worsened both the horizontal and vertical accuracy of the solution. The deterioration of the horizontal accuracy went from 0.17 m with the E5a frequency measurements to 0.74 m with the E1 measurements. The reduction of vertical accuracy went from 0.68 m for the E5a to 1.2 m for the E1 measurements. This was not completely expected as both the HDOP and VDOP parameters decreased when these satellites were included in the solution calculation. However, if precise ephemerides are used instead of broadcast ones, both the horizontal and the vertical accuracy remained stable; actually, for the E5b frequency, the DRMS improved by almost 0.5 m.  
The results achieved show that the real drawback to overcome in order to include the Milena (E14) and Doresa (E18) pseudorange measurements in the single-point positioning algorithms is related to the quality of the broadcast ephemeris. When precise ephemerides are used, we obtained a 5% increase in the number of solutions with an accuracy similar to that obtained when the satellites were excluded.  
The two authors contributed equally to this work.  
This research received no external funding.  
The authors gratefully acknowledge the IGS MultiGNSS Experiment (MGEX) for providing GNSS data and products.  
The authors declare no conflict of interest.