[Federal Register Volume 79, Number 92 (Tuesday, May 13, 2014)]
[Notices]
[Page 27286]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2014-10917]


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DEPARTMENT OF DEFENSE

Office of the Secretary


Global Positioning System Pre-Operational Civil Navigation 
Message

AGENCY: Office of the Secretary of Defense, Office of Public Affairs, 
DoD.

ACTION: GPS notice.

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SUMMARY: The purpose of this notification is to inform users of an 
upcoming event related to the Global Positioning System (GPS) satellite 
constellation. U.S. Air Force Space Command will begin providing pre-
operational, Civil Navigation Message (CNAV) populated L2C and L5 
signals beginning April 28, 2014 in a 2-phase plan, as previously 
highlighted in a Department of Transportation notice that published in 
the Federal Register on March 5, 2014 (79 FR 12563-12564). Based on the 
response to the March 5, 2014 notice, and extensive discussion and 
cooperation between the Office of the Secretary of Defense (OSD) and 
the Department of Transportation, OSD has approved a modification to 
U.S. Air Force Space Command's planned implementation of CNAV. The 
public should consider these broadcasts to be ``use at one's own 
risk,'' since a fully operational command and control and signal 
monitoring infrastructure is not yet in place.

FOR FURTHER INFORMATION CONTACT: Brigadier General David J. Buck, USAF, 
Director of Air, Space and Cyberspace Operations, Department of the Air 
Force, Headquarters Air Force Space Command, 150 Vandenberg Street, 
Suite 1105, Peterson AFB, CO 80914-4170.

SUPPLEMENTARY INFORMATION: The CNAV message broadcasts planned to begin 
in April 2014 will be implemented on all operational GPS satellites 
capable of transmitting the L2C and L5 signals. Currently, seven GPS 
IIR-M satellites broadcast L2C and four GPS IIF satellites broadcast 
L2C and L5. On average, users may expect at least one L2C-broadcasting 
satellite to be in view at all times. The CNAV message content will 
initially include Broadcast Message Types (MT) 10, 11, 30, and 33 (as 
defined in Interface Specification (IS)-GPS-200G and IS-GPS-705C, see 
http://www.gps.gov/technical/icwg/) in lieu of the currently 
transmitted MT-0. The Air Force intends to broadcast L2C messages with 
the health bit set ``healthy,'' as was the case during a June 2013 
test. L5 messages will be set ``unhealthy,'' but as greater experience 
with the L5 broadcast and implementation of signal monitoring is 
achieved, this status will be reviewed and revisited. Should it be 
determined to set the L5 health bit to ``healthy,'' advance 
notification will be made to the public. The CNAV data uploads will be 
integrated into current operations, but initially uploads to each 
appropriate satellite will occur only twice per week. In December 2014, 
CNAV uploads are planned to be at the normal rate of once per day for 
each appropriate satellite. Consequently, users should expect L2C and 
L5 signals with CNAV messages to provide increased user range error 
compared to legacy civil signals between April and December 2014. After 
December 2014, the user range error of the L2C and L5 signals with CNAV 
messages is expected to meet or exceed that of legacy signals. However, 
availability will remain low and CNAV-derived user position accuracy 
may be poor until more L2C and L5 capable satellites are operational. 
Future tests and implementation of the remaining CNAV message types 
will be announced under separate Federal Register notices.
    The pre-operational CNAV messages are being made available for user 
familiarization and for equipment development. The messages will be 
formatted in accordance with IS-GPS-200G and IS-GPS-705C; however, a 
pre-operational signal means the availability and other characteristics 
of the broadcast signal may not comply with all requirements of the 
relevant Interface Specifications. The signals should be employed at 
the users' own risk and should not be used for safety-of-life or other 
critical purposes.

    Dated: May 8, 2014.
Aaron Siegel,
Alternate OSD Federal Register Liaison Officer, Department of Defense.
[FR Doc. 2014-10917 Filed 5-12-14; 8:45 am]
BILLING CODE 5001-06-P