U.S. Air Force Space Command will be implementing CNAV messages on the GPS L2C and L5 signals beginning April 28 at 14:30 UTC, to facilitate user familiarization and development of compatible user equipment. No GPS satellite outages or degradations are planned. The L2C and L5 CNAV messages should be transparent to users.
A 30-day public comment period on the pre-operational CNAV message ended April 4, apparently without enough concern to halt or delay the implementation.
These pre-operational signals may not comply with all requirements, and so shouldn’t be used for safety-of-life or other critical purposes, Air Force Space Command said.
Full text of the NANU appears below:
Subject: New NANU 2014038
NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2014038 NANU TYPE: GENERAL
*** GENERAL MESSAGE TO ALL GPS USERS *** The purpose of this notification is to inform users of an upcoming event related to the GPS satellite constellation. Air Force Space Command will be implementing CNAV messages on the GPS L2C and L5 signals beginning J118/1430z with updates from the control segment approximately twice per week. The message populated signal content will include Broadcast Message Types (MT) 10, 11, 12, 30, and 33. There are no planned GPS satellite outages or degradations for this activity. L2C and L5 CNAV messages should be transparent to GPS receivers that do not process L2C or L5 CNAV messages. These populated signals are intended to facilitate user familiarization and development of compatible user equipment.
NOTE: Until further notice, the L2C and L5 signals are considered pre-operational. 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 and should be employed at the users’ own risk. Therefore these signals should not be used for safety-of-life or other critical purposes. Any military or civil users who encounter user equipment problems following message population of the L2C and L5 signals should contact the applicable POCs identified below as soon as possible. Aviation users should file reports consistent with FAA-approved procedures.
*** GENERAL MESSAGE TO ALL GPS USERS ***
POC: CIVILIAN – NAVCEN AT 703-313-5900, HTTP://WWW.NAVCEN.USCG.GOV
MILITARY – GPS OPERATIONS CENTER at HTTPS://GPS.AFSPC.AF.MIL/GPSOC, DSN 560-2541,
COMM 719-567-2541, firstname.lastname@example.org, HTTPS://GPS.AFSPC.AF.MIL
MILITARY ALTERNATE – JOINT SPACE OPERATIONS CENTER, DSN 276-3514,
COMM 805-606-3514, JSPOCCOMBATOPS@VANDENBERG.AF.MIL