Progressive generations of satellites from GPS II/IIA to GPS III

GPS Modernization

It is the policy of the United States to maintain U.S. leadership in the service, provision, and use of satellite navigation systems. The U.S. government has additional policy goals to meet growing demands by improving the performance of GPS services, and to remain competitive with international satellite navigation systems. Learn more

The GPS modernization program is an ongoing, multibillion-dollar effort to upgrade the GPS space and control segments with new features to improve GPS performance. These features include new civilian and military signals.

In addition to the specific new features noted above, GPS modernization is introducing modern technologies throughout the space and control segments that will enhance overall performance. For example, legacy computers and communications systems are being replaced with a network-centric architecture, allowing more frequent and precise satellite commands that will improve accuracy for everyone.

Program Schedule

The GPS modernization program involves a series of consecutive satellite acquisitions, including GPS IIR(M), GPS IIF, and GPS III. It also involves improvements to the GPS control segment, including the Architecture Evolution Plan (AEP) and the Next Generation Operational Control System (OCX). The schedule for the parallel space and control segment upgrades is shown below. The information on the schedule is correct as of May 2012.

You can select elements of the interactive chart above to learn more about them.

Funding

GPS modernization involves joint funding from the Departments of Defense and Transportation. For more information, visit the Program Funding page. Go there

Ending Selective Availability

The first step in GPS modernization took place in May 2000, when President Bill Clinton directed the Department of Defense to turn off the GPS Selective Availability (SA) feature.

SA was an intentional degradation of civilian GPS accuracy, implemented on a global basis through the GPS satellites. During the 1990s, civil GPS readings could be incorrect by as much as a football field (100 meters). On the day SA was deactivated, civil GPS accuracy improved tenfold, benefiting civil and commercial users worldwide.

In 2007, the government announced that the GPS III satellites will be built without the SA feature.

Learn more about selective availability

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