By Marco Falcone, System Manager for the European Space Agency in the Galileo Project Office
Following the second Galileo launch in October 2012, leading to four operational satellites in orbit, a progressive chain of events has taken place in 2013 encompassing all Galileo Services, starting from the first position fix on March 12 (Figure 1), when navigation message continuous broadcast began.
- Galileo System Time (GST) to Universal Time Coordinated (UTC) dissemination to timing users started on April 16 and since then has been maintained within 5 nanoseconds (Figure 2).
- GPS to Galileo Time Offset (GGTO) dissemination started on April 22, favoring the use of our satellites for combined positioning with the GPS constellation. GGTO accuracy is well within 7 nanoseconds.
- The first implementation of the Galileo Terrestrial Reference Frame (GTRF), aligned to the IGb08, an update of IGS08 (International Terrestrial Reference Frame 2008), has been available since May 27, including all deployed Galileo Sensor Stations sites.
- The capability to disseminate Commercial Service data in the navigation message was demonstrated on June 25.
- In July, several European Union Member States achieved the first position fix using Public Regulated Service (PRS) receivers as part of the EC-ESA joint PRS Participants To IOV (PPTI) campaigns, demonstrating PRS positioning and access control.
- The first search-and-rescue (SAR) localizations using the operational mid-Earth orbit Local User Terminal (MEO LUT) in Maspalomas was exercised July 9, and the first dissemination of the acknowledgement via return link to users in distress was tested in October.
The majority of performance verification tests has been successfully completed as part of the In Orbit Validation (IOV) experimentation campaign completed at the end of October 2013, demonstrating the achievement of the Galileo system’s expected performance. The average positioning accuracy for E1/E5a dual-frequency Open Service users is already around 8 meters horizontally and 10 meters vertically. This is an impressive result considering the small number of Galileo satellites in orbit and the limited ground infrastructure so far.
But the single most important message from the In Orbit Validation campaign is that Galileo works, and it works well.
The experience gained and lessons learned during the IOV period, especially in the domain of ground operations, have been very useful and will be addressed as a priority in the next phase, as part of the planned new versions of the Ground Control Segment and Ground Mission Segment.
The launches in 2014 of the new FOC satellites manufactured by OHB will further increase the availability of positioning and timing accuracy to users.
Complementary system validation campaigns will be carried out next year, moving towards commercial receiver technology for all categories of users, with particular focus on the mass market and the Public Regulated Service. Following the letter issued by the European GNSS Agency to Galileo chipset manufacturers in July 2013, an opportunity has been given to interested companies to take part in a test campaign to support the early introduction of Galileo in commercially available receivers. The campaign will be carried out next year, focusing on the compatibility of the devices with the reception of Galileo Open Service signals and their combined use with GPS and GLONASS. A number of mass-market chipset manufacturers and professional receiver manufacturers have already expressed their interest in participating in the campaign.
Marco Falcone is system manager for the European Space Agency in the Galileo Project Office in Noordwijk, the Netherlands. He has been mission manager for the GIOVE-A and –B satellites, the precursors of the Galileo operational satellite constellation. Nowadays, his main task is to validate the overall Galileo system and to ensure that it fulfils in operations the required performance starting from the first four satellites of the In Orbit Validation Phase throughout the full deployment of the constellation. He received his Master’s degree in computer science from the University of Pisa, Italy and his Master’s degree in space systems engineering from the University of Delft, the Netherlands.