Military of China, force comment.
Military of China, force comment.

United States GPS Site navigation satellite physical map

May 22, 2009 roundup The U.S. Government Accountability Office (GAO) on May 7, issued a report on the GPS. GAO said in a report, not sure whether the timely access to new U.S. Air Force satellites, maintaining the existing GPS services are not interrupted. Task tardiness and cost overruns have been caught in the whole system collapse.

a release on the report attracted widespread media attention. If you can not launch a new satellite global positioning system to compensate for the deficiencies caused by aging, so hundreds of millions of civilian and military GPS accuracy and reliability of the device will be greatly reduced. U.S. Air Force responded by saying that it has many ways to keep the normal operation of the navigation system.

the next generation of GPS satellites for the GPS IIF satellites, launch has been delayed by problems and budget overruns. Boeing said the contractor, the launch delay is necessary due to design changes. Has been completed,’s first IIF satellite is expected to launch in November 2009, compared with the schedule pushed back about three years.

GAO said, the main risk comes from and then the next generation of satellite GPS IIIA, it also delayed a similar time. Lockheed Martin is building the satellite in the series, IIIA satellite program’s first launch in 2014.

While it is widely used in civil, but the GPS was originally developed for the military, now remain with the Air Force management. U.S. Air Force’s mission is to maintain the GPS constellation of 24 satellites run work to ensure that at any time over any point on Earth at least four satellites at work, this is a GPS device to calculate its own position of the minimum required for satellite number.

GPS satellites do not always work: a few in the early 1990 launch of the satellite is still running, but most have stopped working. IIF series satellite launch means that the extension of a few years the update rate may not keep up with the satellite failure rate.

GPS U.S. Air Force Space Command, responsible for the affairs official Lewallen said the GAO agreed to downgrade the risk of possible services to the conclusions. But he said that this risk is very small, GPS system has sufficient spare capacity. Now there are 30 tracks on working satellites, plus three may be re-activated the old satellite. Also a GPS IIR (M) satellite is also ready to launch in August 2009, the $ 30 billion system had never had such a large and precise.

Lewallen said that if some of the satellite fails, there are other ways to extend the life of existing satellites. For example, the Air Force to maintain the GPS signal power, can turn off the satellite and other features. Most of these satellites is a secret sub-capabilities, but the public know of the GPS satellites carry sensors that can detect nuclear explosions.

Stanford University GPS Research Laboratory, Professor Per Enge aeronautics, said the Air Force has developed a good interstitial measures, but they do not always work. Enge would like to see more countries agree to maintain the minimum number of satellites, perhaps 30. Enge said the most important thing is to give the GPS sustained financial support. (China Aerospace Engineering Consultation Center Xie Huimin Money,)