A global navigation satellite system seems like such solid thing, like the pyramids, perhaps, or a mountain. Permanent, fixed, immutable.

Nor is this surprising. After all, GNSS distinguishes itself from many other technologies of the moment by its grounding in a large and widespread infrastructure: a master control station, launch facilities, far-flung monitoring stations, the space segment with dozens of massive satellites that can operate 20 years or more as did a recently retired GPS Block IIA spacecraft.

From the user perspective, even those unaware of the tons of metal and electronics behind the signals their devices receive, the persistent and robust availability of the resource historically only adds to an expectation of continuity.

But that sense of unchanging permanence is deceptive. Indeed, a GNSS program is in constant motion, reaching for the future even as it secures its present with the labor and investments of the past.

Every GNSS program in existence today, including regional systems, is undergoing constant change — modernizing, evolving, expanding: the Global Positioning System with its GPS Block III program and next-generation operational control system, BeiDou moving from Phase II to Phase III as the system progresses toward a global presence, GLONASS working to bring new signals online with new satellites while completing a System of Differential Correction and Monitoring.

Even Europe, with only about a third of its initial Galileo space segment in place, began looking beyond its projected completion in 2020 with a formal GNSS “evolution” initiative launched in 2007. To gather more insight into how one GNSS program got out ahead of its inevitable modernization needs, we called on Prof. Dr. Günter Hein.

Hein was the head of the EGNOS and GNSS Evolution Department at the European Space Agency (ESA) from December 2008 until the end of 2014. He continues to organize the ESA/JRC International Summer School on GNSS, was appointed 2015 by the University FAF Munich as Emeritus of Excellence, and is now a member of the Executive Board of Munich Aerospace.