NavSAS Group Acquires, Tracks Second Galileo IOV Satellite

On January 17, the E1 signal of the Galileo Flight Model 2 satellite (FM2, also known as GSAT0102) was successfully acquired and tracked by the researchers of the Navigation, Signal Analysis and Simulation (NavSAS) group (Politecnico di Torino / Istituto Superiore Mario Boella) for the first time at 11:54:10 CET (10:54:10 UTC).

This signal has been received at the Istituto Superiore Mario Boella (ISMB) premises (located in Torino, Italy, latitude = 45°03'54.99" N, longitude = 7°39'32.29" E, height = 311.97 meters) with a non-directive GNSS antenna, a commercial narrowband E1 RF front-end, and the N-GENE receiver, a fully software receiver developed by the NavSAS researchers.

The FM2 satellite currently broadcast a Galileo Open Service signal on E1 band using the Code Number 12 of the Galileo Interface Control Document (ICD). It is the second of the two Galileo In-Orbit Validation (IOV) satellites launched on October 21, 2011. The first IOV satellite — the Galileo-ProtoFlight Model (PFM) spacecraft — was received by NavSAS researchers for the first time on December 12.

Both the PFM and the FM2 satellites were in view January 17, and their E1 signals have been successfully received and processed.

Figure 1 and 2 show the orbits of the two Galileo satellites at the moment of the signal acquisition. These screenshots have been produced by a free software tool (Orbitron, by Sebastian Stoff). In Figure 1 the two satellites, denoted as GALILEO-PFM GALILEO-FM2, are visible. Figure 2 shows a detailed skyplot computed in Torino, Italy.

Figure 1. Galileo IOV satellite orbits at the moment of the signal acquisition.

Figure 2. Skyplot of Galileo IOV satellite orbits at the moment of the signal acquisition.
 

The Galileo FM2 satellite signal (PRN 12) has been successfully acquired for the first time at 11:54:10 and the first acquisition and tracking results are reported from Figures 3 to Figure 6. It can be noticed that the satellite signal was received with a C/N₀ of approximately 46.4 dBHz and a Doppler frequency shift equal to -2595 Hz.

Figure 3. Search space of the successful acquisition of the Galileo FM2 satellite (PRN 12).

Figure 4. Zoom on the peak obtained acquiring the Galileo FM2 satellite (PRN 12).

Figure 5. Estimated C/N₀ and correlation values obtained tracking the PRN 12.
 

Figure 6. Estimated Doppler values obtained tracking the PRN 12.
 

Also, the Galileo PFM satellite was in view on January 17, and the signals from both satellites have been measured and compared by the NavSAS researchers. Figure 7 shows the elevation patterns of PFM and FM2 satellites as obtained from prediction visibilities based on NORAD tracking information (two-line elements of Galileo satellites downloaded on January 17). Figure 8 shows both the estimated Doppler and C/N₀ profiles obtained from multiple measurements performed on the same time interval: their trends agree with the satellite elevations shown in Figure 7.

Figure 7. Elevation pattern versus time of the PFM and FM2 satellites over Torino on January 17.

Figure 8. Estimated Doppler and C/N₀ profiles along multiple measurements performed on January 17.

As a final step, the demodulation of the E1b data channel has also been performed, checking the navigation messages for both the satellites. It has been noticed that, at the moment, the navigation messages present only two types of page: reserved (word type field with value 63) and type 0 (spare). Type 0 words have valid Week Number and Time Of Week fields. On the other hand, both the satellites broadcast a valid secondary code on their E1c pilot channels, compliant with the Galileo ICD.