WASHINGTON — As 2017 winds down, the GPS 3 constellation finally has a string of victories for the Air Force to celebrate. The first satellite is on track for a 2018 launch. The digital navigation payload has been fixed after earlier setbacks, and units are in production. And the ground-control software is starting to recover from years of schedule delays.

To top it off, the Government Accountability Office this month gave the new constellation some schedule breathing room. It projected that the current constellation of 31 GPS 2 satellites will remain operational until 2021 — two years longer than previously estimated. The Air Force is on a path to start operating the GPS 3 constellation by June 2021 as there are seven satellites planned to be launched by then.

But there’s also bad news. Government auditors have warned that the GPS 3 program increasingly is becoming harder to manage because of the complexity and scope of the upgrades required to military weapon systems to receive the encrypted signals. The satellites might be up and running by 2021 but it could take many more years to get the ground infrastructure and equipment terminals in synch with the new satellites.

Things began to get more complicated due to a five-year delay in the operational control system software, known as OCX. To fill the gap, the Air Force started two new programs in 2015 to modify the current ground systems so they could control GPS 3 satellites and provide an encrypted broadcast. As a result, there are five programs under GPS modernization: the satellites, OCX, military user equipment, contingency operations and military code (M-code) early use.

While the satellite constellation is moving forward on a predictable schedule, the M-code software and the receivers needed to acquire that signal could take a lot more time and money to test and install in major U.S. weapon systems than the Pentagon expected.

The watchdog agency labeled the M-code early use a “high risk” effort. “Additional development is necessary to make M-code work with over 700 weapon systems that require it,” said GAO analyst Christina Chaplain. The Defense Department has started the transition for some weapon systems, “but more remains to be done to understand the cost and schedule needed to transition to M-code receivers.”

If the Air Force fails to successfully synchronize the multiple elements of the GPS 3 systems — some of which are funded and managed outside the Air Force — the military is at risk of deploying a brand new satellite constellation years before the terminals and user software are in place.

Chaplain said the transition from existing GPS receiver cards to M-code receiver cards is likely to take more than a decade. “As a result, DoD anticipates that war fighters will have to operate with a mix of older and newer receiver cards.”

In December 2016, the Pentagon procurement office asked the military services, the Missile Defense Agency and U.S. Special Operations Command for specific M-code implementation plans, projected costs and schedules. That information was submitted in February 2017. They identified 716 types of weapon systems that require almost a million M-code receiver cards.

GAO estimated it will cost more than $2.5 billion to integrate and procure M-code receiver cards on only a small number of weapon systems out of the hundreds of types that need M-code receiver cards. “The full cost will be much larger — likely many billions of dollars.”

The Army and Marine Corps fleet of light tactical trucks alone will eventually need almost 25,000 receiver cards. Of the 716 types of weapon systems that will need M-code receiver cards, only 28 — or less than 4 percent — are funded through fiscal year 2021.

Even of greater concern for DoD is that these estimates do not include funding beyond fiscal year 2021 that will be needed for further development, integration, and procurement. This means that DoD and Congress still don’t know how much additional funding could be needed for the remaining 96 percent of all weapon systems that need M-code receivers.

GPS 3 is one of dozens of major defense acquisition programs that are no longer centrally managed from the Pentagon and have been transitioned to the military services. The GAO suggested the secretary of defense should keep an eye on the M-code receiver card acquisition planning, and “assign an organization with responsibility for systematically collecting integration test data, lessons learned, and design solutions and making them available to all programs expected to integrate M-code receiver cards.”

According to the Air Force, GPS 3 will have three times better accuracy and up to eight times improved anti-jamming capabilities compared to the current satellites. A new L1C civil signal will make it the first GPS satellite to be interoperable with other international global navigation satellite systems like Galileo.

Satellite manufacturer Lockheed Martin announced this month that the first GPS 3 successfully “talked” with the OCX system on the ground. This is the first of 10 satellites Lockheed will build for the Air Force. Raytheon is the prime contractor for OCX.

The first GPS 3 satellite was declared “available for launch” in September, and it is expected to go into orbit in March 2018.

Navigation payload manufacturer Harris Corp. announced last week it delivered the fourth of 10 units. It expects to ship four more in 2018. Harris is under contract to Lockheed Martin. At the heart of the digital navigation payload is a “mission data unit” that links atomic clocks, radiation-hardened computers and powerful transmitters — enabling signals three times more accurate than those on current GPS satellites.

Sandra Erwin writes about military space programs, policy, technology and the industry that supports this sector. She has covered the military, the Pentagon, Congress and the defense industry for nearly two decades as editor of NDIA’s National Defense...