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AFSPC Tests GPS Civil Signals L2C and L5

By Air Force Space Command Public Affairs / Published June 14, 2013

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PETERSON AIR FORCE BASE, Colo. – As part of the GPS Modernization effort, the Space and Missile Systems Center, Global Positioning Systems Directorate (SMC/GP) will execute Civil Navigation (CNAV) message testing in June 2013 and will execute similar tests at least annually.

SMC/GP has drafted their test plan and incorporated inputs from vendors, civil agencies, and the user community.  SMC/GP will conduct live-sky CNAV testing with non-operational signals prior to deployment of the Next Generation Operational Control System (OCX) to ensure readiness for transition to operations and enterprise-level readiness to broadcast the modernized GPS open-service signals, L2C and L5.   The current GPS operational control system, Architecture Evolution Plan, does not support generation of CNAV messages but OCX will provide this capability when it comes online in 2016.  To support CNAV testing, SMC/GP has developed offline test tools to generate CNAV messages for upload to the operational IIR-M and IIF satellites.  This capability allows the program office to mitigate development risk and ensure readiness of next-generation modernized Signal-In-Space (SIS) capabilities.  Periodic test broadcasts will support user equipment development and early compatibility evaluation and present an opportunity for early operational use. 

Day-to-day operations of the GPS constellation are conducted by the 2nd Space Operations Squadron.  Officials anticipate no impact to operational users throughout the testing period.

In 2008, the US government announced a sunset date of December 31, 2020 for support of GPS semi-codeless P(Y)-code users and encouraged transition to L2C and L5.  CNAV testing will be visible to all current L2C and L5-capable receivers.  The current GPS L2C and L5 signals have only default message information.  While it is unknown how many fielded L2C and L5 user receivers, process the CNAV message types, SMC/GP included the public in the test planning process by way of Federal Register Announcement, to notify all of the CNAV testing.  User and receiver development community involvement will enhance team expertise in the planning process and AFSPC encourages public participation during test planning and execution, to obtain the broadest, most consensus-driven approach possible for testing of the civil capabilities.

Live-sky test broadcasts provide the most operationally relevant opportunity to evaluate the new civil signals and fielded receivers and will also accelerate development of CNAV Concept of Operations.  Active testing will also motivate the development of compatible receivers and civil community readiness for operational broadcast of the new signals, in preparation for OCX ready transition to operations (RTO).

The structure and content of all defined CNAV messages broadcast during live-sky testing are based on applicable SIS Interface Control Documents and Interface Specifications; however, new CNAV messages may be defined within the test plan.  The new flexible CNAV messaging structure warrants extensive testing of the different CNAV message types, message contents, and message delivery intervals to prepare OCX for RTO in mid-2016 and to ensure CNAV messages are of the highest utility to the GPS world community.

For more information contact AFSPC Public Affairs at (719) 554-3731.