The in-orbit validation of Galileo has been achieved, according to the European Space Agency (ESA). Europe now has the operational nucleus of its own satellite navigation constellation in place — the world’s first civil-owned and operated satnav system.
Four is the minimum number of satellites needed to perform navigation fixes. In 2011 and 2012, the first four satellites were launched into orbit. In 2013, these satellites were combined with a growing global ground infrastructure to allow the project to undergo its crucial in-orbit validation phase: IOV.
“IOV was required to demonstrate that the future performance that we want to meet when the system is deployed is effectively reachable,” said Sylvain Loddo, ESA’s Galileo Ground Segment manager. “It was an intermediate step with a reduced part of the system to effectively give evidence that we are on track.”
On March 12, 2013, Galileo’s space and ground infrastructure came together for the first time to perform the historic first determination of a ground location, taking place at ESA’s Navigation Laboratory in the ESTEC technical centre, in Noordwijk, the Netherlands. From that point, generation of navigation messages enabled full testing of the entire Galileo system. A wide variety of tests followed, carried out all across Europe.
“ESA and our industrial partners had teams deployed in the field continuously for test operations,” said Marco Falcone, ESA’s Galileo System Manager. “More than 10,000 km were driven by test vehicles in the process of picking up signals, along with pedestrian and fixed receiver testing. Many terabytes of IOV data were gathered in all.”
The single most important finding from the test results? Galileo works, and it works well. The entire self-sufficient system has been shown as capable of performing positioning fixes across the planet.
Galileo’s observed dual-frequency positioning accuracy is an average of 8 meters horizontal and 9 meters vertical, 95 percent of the time. Its average timing accuracy is 10 billionths of a second. Its performance is expected to improve as more satellites are launched and ground stations come on line.
For Galileo’s search and rescue function — operating as part of the existing international Cospas–Sarsat programme — 77 percent of simulated distress locations can be pinpointed within 2 kilometers, and 95 percent within 5 kilometers. All alerts are detected and forwarded to the Mission Control Centre within a minute and a half, compared to a design requirement of 10 minutes.
“Europe has proven with IOV that in terms of performance we are at a par with the best international systems of navigation in the world,” said Didier Faivre, ESA director of Galileo and Navigation-related Activities.
In an article for The System section of the February 2013 GPS World, Peter Steigenberger, Urs Hugentobler, and Oliver Montenbruck discuss Galileo-only positioning. “Using an ionosphere-free dual-frequency linear combination of pseudorange measurements on the Galileo E1 and E5a frequencies, the position of the TUME reference station [at the Technische Universität München (TUM) in Munich, Germany] could be determined with a 3D position error of less than 1.5 meters,’” the authors said. Read more here.