New 24+3 GPS Configuration Will Increase Accuracy

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Moving three existing GPS satellites to new orbit locations will have a profound effect on GPS capabilities for all civil, commercial, and military users worldwide.

The U.S. Air Force Global Positioning Systems Wing and the 50th Space Wing have announced a reconfiguration: the 24+3 GPS constellation plan or “Expandable 24,” with timeline as follows:

“The [24+3] initiative will take up to 24 months to fully implement as satellites are repositioned within the constellation based on constellation health. The beneficial impact to all GPS users, including civilian users, will be slowly realized during that time period. Over the next two years, the number of GPS satellites in view from any point on earth will increase, potentially increasing accuracy of GPS receivers.”

The plan will significantly alter the current configuration, which consists of indeed 30 GPS satellites in MEO or medium earth orbit that are used globally, however many of the additional satellites are currently flown in tandem, side by side, with considerably older satellites and effectively limit the constellation geometry to that of 24 satellites.

Further details will come in this week’s Defense PNT newsletter, in a column by GPS World contributing editor Don Jewell.

Meanwhile, the Wing and GPS 50th Space Wing also announced that they “are ushering in improved Global Positioning System (GPS) capabilities through a new ground system software release. New capabilities include telemetry, tracking and commanding for the new GPS IIF space vehicle and robust security improvements. The planned transition at Schriever Air Force Base on January, 11, 2010, is the result of extensive testing to ensure this upgrade is transparent and has no impact to military and civil users."

The Space Wing continued, "With the pending mid-2010 launch of the first GPS IIF space vehicle, the ground system is prepared to command the new on-orbit GPS IIF capabilities which include a new navigation signal for civil users, encrypted military code, crosslink enhancements, improved navigation signal accuracy and signal power increases. The new software also provides robust security improvements to include 'over-the-air' distribution of encryption keys to properly equipped military users. Preparation for activation of the new software included rigorous developmental and operational testing events including five transition exercises. The new ground system software commanded current individual GPS satellites during numerous testing events and rehearsals. In November and December 2009, the new software successfully uploaded operational GPS IIA and IIR space vehicles with navigation data and completed normal operational functions. This improvement initiative continues the Air Force’s commitment to the global community of GPS users."

The GPS Wing statement continued, "The U.S Air Force and Air Force Space Command have been the diligent stewards of GPS since its conception in the 1970s and continue its commitment to this critical component of our National Infrastructure. The current GPS constellation has the most satellites and the greatest capability ever. We are committed to maintaining our current level of service, as well as 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 military and civilian users around the world."

The Air Force Space Command’s Space and Missile Systems Center, located at Los Angeles Air Force Base, Calif., is the U.S. Air Force’s center of acquisition excellence for acquiring and developing military space systems including six wings and three groups responsible for GPS, military satellite communications, defense meteorological satellites, space launch and range systems, satellite control network, space based infrared systems, intercontinental ballistic missile systems and space situational awareness capabilities.

source: GPS World