GPS performance could degrade but won't fail, Air Force says

Computerworld - The Global Positioning System used by the U.S. military -- and millions of motorists around the world -- is not in danger of going down, although there is some risk of degraded performance as reported by the investigative arm of the U.S. Congress, an Air Force colonel said in a Twitter forum.

"No, the GPS will not go down," said Col. Dave Buckman, command lead for position, navigation and timing at the Peterson Air Force Space Command in Colorado. However, citing an earlier report by the Government Accountability Office, Buckman added, as the "GAO points out, there is potential risk associated with a degradation in GPS performance."

Buckman commented during a one-hour session yesterday on the command's Twitter page. A transcript of the questions and answers appears on the command's Web site.

The Global Positioning System, which is now made up of 31 operational satellites, is a free service provided by the U.S. government. Nearly $6 billion is allocated over the next five years to provision new GPS satellites and ground control facilities, according to government records.

Buckman is the Peterson Air Force Space Command's subject matter expert on the GPS program, which has been under the stewardship of the U.S. Air Force and the command since its inception in the 1970s. A short statement on the command's site attempts to reassure the public that the GPS setup is secure.

"The current GPS constellation has the most satellites and the greatest capability ever," the statement says. "We are committed to maintaining at least our current level of service, while striving to improve service and capability through on-going modernization efforts. The Air Force will continue to pursue an achievable path maintaining GPS as the premier provider of positioning, navigation and timing for the military and civilian users around the world."

Buckman's Twitter comments came in response to GAO testimony May 9 before a subcommittee of the U.S. House Committee on Oversight and Government Reform, which questioned the GPS's future performance.

"It is uncertain whether the Air Force will be able to acquire new satellites in time to maintain current GPS service without interruption," Christina Chaplain, director of GAO acquisition, said in her testimony.

In another tweet, Buckman admitted there have been space command problems in upgrading the navigation system, including a satellite launched in March that is still not fully deployed above Earth. The satellite, SVN-49, has been sending "unusual performance data," Buckman said, but the command is troubleshooting it and "making good progress." Buckman and officials at the space command could not be reached for further details.

However, in early May, a blogger on the InsideGNSS Web site -- which is devoted to "engineering solutions from the global navigation satellite system community" -- said that SVN-49's problems could prevent it from being declared healthy for months, if ever.

Buckman also said two efforts are underway to update the fleet of GPS satellites. "Agree w/GAO there's a potential risk, but GPS isn't falling out of the sky -- we have plans to mitigate risk and prevent a gap in coverage," he added.

He also said it is "very unlikely" that users will notice a decline in GPS accuracy. The next satellite designed to maintain the current service level is set to launch in August, he added.

The GAO reported that 31 satellites are being used when only 24 are required to keep the GPS service for civil, commercial and military users above a 95% probability of staying within acceptable performance standards.