Three GPS Satellites Moved Into New Positions for More Robust, Accurate Signals

January 25, 2011

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(Update June 15, 2011 Inside GNSS) Completion of Satellite Repositioing Optimizes GPS Constellation

By next June, the United States GPS constellation will attain the most optimal geometry in its nearly 33-year history. Over time, that means a more robust signal, more accuracy and more reliability in GPS-challenged environments.

The 50th Space Wing is in the middle of maneuvering six GPS satellites into more favorable positions. The two-phase operation, called "Expandable-24" is halfway to completion.

Phase one began on January 13, almost exactly one year ago. The 2nd Space Operations Squadron, the Wing unit that controls GPS, began maneuvers on three selected satellites: SVN 24, SVN26 and SVN 49. One took 351 days to nudge into place. The third satellite completed repositioning on January 18, 2011.

Phase two of Expandable-24 began in August 2010 and is expected to be finished next June. Another three Three GPS satellites will be repositioned during the second phase.

The current GPS constellation has six more satellites in working order than the 24 it needs to make sure the system is fully operational 95 percent of the time. Before Expandable-24, the constellation geometry did not maximize the use of the extra satellites.

The 50th Space Wing (50 SW) manages the Global Positioning System and announced the completion of Phase I. The wing is under U.S. Air Force Space Command (AFSPC). The 50 SW is host wing (operator and administrator) at Schriever Air Force Base in Colorado. Their primary responsibility is to track and maintain the command and control, warning, navigational, and communications satellites for AFSPC.

The Air Force launched the first GPS satellite launch in February 1978. Full operational capability (FOC) with 24 satellites on orbit was declared in 1995.