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Agencies try to calm fears about GPS problems

Beneath the Twitter sessions, media interviews and briefings, there is a surprising undertone in the ongoing U.S. effort to restore faith in the GPS navigation satellites following a report by the Government Accountability Office warning of possible loss of GPS accuracy.

The report has been a mixed blessing. On the downside, at least in the view of GPS managers, the congressional investigators caused “undue worry” among users, said Col. Dave Madden, who runs the constellation. Those users include U.S. troops, some of whom had to wonder about the tales of a pending GPS “blackout” that went viral on the Internet. The GAO never used that term, but countless bloggers and some news stories did.

In the wake of it all, the GAO’s Cristina Chaplain, who oversaw the investigation, now says she regrets the “turmoil” the report has caused for the Air Force. She says this while standing by her team’s findings, which she notes the Pentagon “fundamentally” concurred with in a letter attached to the report.

Still, there are the bloggers.

“It got very exaggerated. It was suggested that satellites could start falling out of the sky,” she said. “A 10 percent probability of going below 24 satellites” — the minimum constellation required for expansive coverage and highly accurate position readings — “is not the same as no service.”

“That put a lot of stress on the Air Force, which wasn’t our intention. We want them focused on the program,” she said.

Chaplain said she has spoken to Air Force officials, and the two sides agreed they should share more information, not less, in the wake of the controversial report. The GAO does not do clarifications, Chaplain said, but her office is working on a follow-on study at the request of a congressional subcommittee.

The upside could be this: The Obama administration’s $927.8 million budget request for GPS work in 2010 is moving relatively unscathed through Congress. The money would go toward construction of 12 GPS 2F satellites by Boeing, and development by Lockheed Martin of a next-generation version called the GPS 3A, together with the control system for it. These are the satellites that must be constructed on time and successfully rotated into the GPS constellation, an array of 31 satellites in middle Earth orbit, 12 of which are between 13 and 16 years old. A user needs to lock on to at least four satellites for an acceptably accurate fix, and 24 satellites must be operating to give adequate coverage.

The GAO report “helps because it puts a lot of emphasis on the budget for future satellites and things like that,” said Col. Robert Hessin, acting director of the National Coordination Office for Space-based Positioning, Navigation and Timing, a government agency that tracks GPS legislation and the health of the constellation.

Where it hurts, he said, is on the international front, where China, Russia and Europe are developing their own satellite navigation systems. “We’re competing with the rest of the world on precision navigation,” Hessin said.

The GAO report chipped away at confidence in the U.S. system among allies and commercial users, he said.

U.S. defense policy has long called for keeping GPS the international gold standard for precision navigation and the timing signals on which banks and mobile phone companies rely to keep their wireless communications from colliding over the airwaves. The thinking is that China or Russia would be less likely to attack the GPS constellation if their economies and those of their allies were tied to an international precision navigation and timing system dominated by GPS.

Clearing the record

Air Force Space Command is attempting to use the Internet to clear the record. In May, a month after the GAO report was issued, the command organized a forum on the Twitter social networking service in which managers fielded such questions as: “Is there any actual probability of the GPS systems going down in 2010, or is it just worst-case scenario — like my commute?” The answer from a Space Command official: “No, the GPS will not go down. GAO points out, there is potential risk associated with a degradation in GPS performance.”

For the record, the GAO investigators used the word “interruption,” but taken in the full context of the report, they meant that the high accuracy of the positioning readings — currently to within a meter — could be interrupted. Not the entire GPS service.

How does Hessin assess the risk? “I’m going to answer, but you’re not going to believe me: This constellation is as robust I’ve ever seen the constellation.”

The constellation consists of 30 operational spacecraft right now, with three on-orbit “residual” satellites. The 31st satellite is a recently launched GPS 2R spacecraft that is not operating properly. Madden said its performance is within the 6-meter minimum required, but the Air Force is attempting to improve the accuracy through software commands.

As for what might happen in 2010 — the year referenced in the GAO report — the viral reports sprang from a single passage in the report, one that Chaplain now admits does not track logically. The passage reads: “If the Air Force does not meet its schedule goals for development of GPS 3A satellites, there will be an increased likelihood that in 2010, as old satellites begin to fail, the overall GPS constellation will fall below the number of satellites required to provide the level of GPS service that the U.S. government commits to.”

The first 3A satellite is not scheduled for launch until 2014, so those satellites could not affect GPS services in 2010. But some of the satellites could die in 2010, which would make it urgent to get the 3As up as soon as possible. Chaplain said she would check with her team to see if that’s what the controversial passage should have said.

Even then, Madden suggested he does not agree with the GAO’s conclusion about the old satellites. “We expect some of them to be around for at least another three to four years,” he told reporters.