GPS Service Could Fall in Reliability May 20, 2009Posted by Bahadir Sahin in English, Haber (News).
Tags: Air Force GPS program, GPS accuracy and coverage, GPS civilian users, GPS signal acquisition, next-generation satellites
GPS service may fall to a reliability level below 95 percent and periodically dip below 80 percent over the next five years, concluded the government watchdog agency, the Government Accountability Office (GAO).
In addition, OnStar, which testified before a House of Representatives subcommittee earlier this month, said, “We are concerned that a recent report shows eight of the current [GPS] satellites are one component from total failure,” according to Chet Huber, OnStar president. He added that GPS accuracy and coverage could be affected.
The GAO study was presented to Congress on May 7, at which time several experts, including Huber, testified on the topic.
In short, the GAO study found efforts to acquire new satellites by the Air Force, which is in charge of GPS signal acquisition, have been delayed in part by technical problems. The launch of the first satellite in the Air Force’s IIF satellite program is three years late, due to launch in November 2009. The program is currently $870 million over its original budget.
A second Air Force GPS program to deploy next-generation satellites might also face delays, said the report and this will increase the “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 report said GPS civilian users could be affected by these delays. It said, “The estimated long-term probability of maintaining a constellation of at least 24 operational satellites falls below 95 percent during fiscal year 2010 and remains below 95 percent until the end of fiscal year 2014, at times falling to about 80 percent.”
A Garmin spokesman responded, “We firmly believe there is no reason to fear a significant or serious outage in service.”
He added, “While we do think that the various government entities need to work better together to avoid delays and cost over-runs, the situation is not as dire as has been portrayed.”
Some industry members noted privately that consumer GPS devices are 12-channel devices, tracking only 12 of 24 satellites at any one time. They also suggested the government is not likely to let the GPS system fail.
The U.S. maintains a constellation of 24 GPS satellites operational at any one time, plus spares.
To solve these problems, the report recommends that the Secretary of Defense appoint a single authority to oversee GPS programs as space programs are typically hampered by frequent turnover in program managers.
The GOA is an independent, nonpartisan agency that works for Congress and is headed by the Comptroller General of the U.S.