The successful launch of the U.S. Navy’s fourth Mobile User Objective System communications satellite Sept. 2 rounds out a multibillion-dollar constellation that has been in development for more than a decade.

Navy officials hailed the launch as a milestone toward bringing unprecedented smartphone-like communications capabilities to otherwise “disadvantaged” users — typically mobile forces, operating in hard-to-reach areas, such as beneath jungle canopies — around the world.

But the launch is also a reminder that more than three-and-a-half years after the February 2012 launch of the first satellite, some two years behind schedule, the MUOS system’s advanced capabilities remain unavailable.

Each MUOS satellite carries a legacy UHF narrowband payload that is roughly equivalent to one of the previous generation UHF Follow-On satellites, eight of which were still operating as of a year ago. But the system’s breakthrough capability is a digital payload employing 3G mobile communications technology to support 10 times the number of users as the legacy systems with simultaneous voice and data services. MUOS also will enable users to communicate from anywhere on the globe; conversations over the UHF Follow-On system are confined to users within the coverage footprint of the same satellite.

But these advanced capabilities, which were supposed to become available with the second satellite, are going to have to wait until the end of the year, at least. According to a Navy report sent to Congress late last year, final certification testing for MUOS has been postponed until this coming December due to integration issues between the radio-frequency wave form for the MUOS digital payloads and the system’s U.S. Army-developed user terminals. Previously that testing was slated for April 2014.

Whether the issue is strictly between the payload and user equipment — poor development coordination between U.S. military satellites and terminals is a longstanding problem — or due in part to problems with the payload itself is not clear. But until this is resolved, MUOS is little more than a very expensive extension of the legacy system.

So while the launch of the fourth satellite indeed represents tangible and notable progress, it is of the incremental variety. For a system whose total estimated cost to taxpayers is more than $7 billion, the victory celebration is going to have to wait until the system proves it can deliver as advertised.

Brian Berger is editor in chief of and the SpaceNews magazine. He joined in 1998, spending his first decade with the publication covering NASA. His reporting on the 2003 Space Shuttle Columbia accident was...