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, HTTPS://WWW.NAVCEN.USCG.GOV MILITARY - GPS WARFIGHTER COLLABORATION CELL at HTTPS://GWCC-WS.CCE.AF.MIL/GPSOC, DSN 560-2541, COMM 719-567-2541, gpsoperationscenter@us.af.mil, HTTPS://GWCC-WS.CCE.AF.MIL MILITARY ALTERNATE - JOINT SPACE OPERATIONS CENTER, DSN 276-3526. COMM 805-606-3526. JSPOCCOMBATOPS@US.AF.MIL 2014039------------------------ NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2014039 NANU TYPE: GENERAL *** GENERAL MESSAGE TO ALL GPS USERS *** Reference NANU 2014038. Update: The purpose of this notification is to inform users that the CNAV messages on the GPS L2C and L5 signals beginning on approximately J118/1430z, will include Broadcast Message Types (MT) 10, 11, 30, and 33, but will exclude Broadcast MT 12. Additionally, the CNAV message health bits will indicate that the L1 and L2 signals are healthy, but that the L5 signal is unhealthy. The CNAV message health bits may function independently from the Legacy message health bits and should not be considered reliable indicators of signal quality or performance during pre-operational use. REMINDER: 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, HTTPS://WWW.NAVCEN.USCG.GOV MILITARY - GPS WARFIGHTER COLLABORATION CELL at HTTPS://GWCC-WS.CCE.AF.MIL/GPSOC, DSN 560-2541, COMM 719-567-2541, gpsoperationscenter@us.af.mil, HTTPS://GWCC-WS.CCE.AF.MIL MILITARY ALTERNATE - JOINT SPACE OPERATIONS CENTER, DSN 276-3526. COMM 805-606-3526. JSPOCCOMBATOPS@US.AF.MIL 2025017------------------------ NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2025017 NANU TYPE: GENERAL *** GENERAL MESSAGE TO ALL GPS USERS *** Testing will be occurring through CY 2025 using PRNs 35, 36, 37 on residual SVs broadcasting UNHEALTHY navigation messages. *** GENERAL MESSAGE TO ALL GPS USERS *** POC: CIVILIAN - NAVCEN AT 703-313-5900, HTTPS://WWW.NAVCEN.USCG.GOV MILITARY - GPS WARFIGHTER COLLABORATION CELL at HTTPS://GWCC-WS.CCE.AF.MIL/GPSOC, DSN 560-2541, COMM 719-567-2541, gpsoperationscenter@us.af.mil, HTTPS://GWCC-WS.CCE.AF.MIL MILITARY ALTERNATE - JOINT SPACE OPERATIONS CENTER, DSN 276-3526. COMM 805-606-3526. JSPOCCOMBATOPS@US.AF.MIL 2025067------------------------ NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2025067 NANU TYPE: GENERAL *** GENERAL MESSAGE TO ALL GPS USERS *** On 29 September 2025, GPS will transition SVN 51 (PRN 20) into the broadcast almanac for all satellites. The almanac transition, accomplished one satellite at a time, will require approximately 24 hours to complete. Before, during, and after transition SVN 51 (PRN 20) will remain unusable until further notice. Future NANUs will notify users of any changes to the above stated status. On approximately 30 September 2025, SVN 51 will resume transmitting L-band utilizing PRN 20. *** GENERAL MESSAGE TO ALL GPS USERS *** POC: CIVILIAN - NAVCEN AT 703-313-5900, HTTPS://WWW.NAVCEN.USCG.GOV MILITARY - GPS WARFIGHTER COLLABORATION CELL at HTTPS://GWCC-WS.CCE.AF.MIL/GPSOC, DSN 560-2541, COMM 719-567-2541, gpsoperationscenter@us.af.mil, HTTPS://GWCC-WS.CCE.AF.MIL MILITARY ALTERNATE - JOINT SPACE OPERATIONS CENTER, DSN 276-3526. COMM 805-606-3526. JSPOCCOMBATOPS@US.AF.MIL 2025075------------------------ NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2025075 NANU TYPE: GENERAL *** GENERAL MESSAGE TO ALL GPS USERS *** NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2025075 NANU TYPE: GENERAL *** GENERAL MESSAGE TO ALL GPS USERS *** Testing will be starting no earlier than JDAY 315 (11NOV25) using PRN 34 with the third Navigation Technology Satellite (NTS-3) and is planned to continue through June 2027. GPS users should not attempt to track or use the signals transmitted by NTS-3 since they will not be IS/ICD compliant. *** GENERAL MESSAGE TO ALL GPS USERS *** POC: CIVILIAN and MILITARY - AFRL.RV.NTS3@us.af.mil *** GENERAL MESSAGE TO ALL GPS USERS *** POC: CIVILIAN - NAVCEN AT 703-313-5900, HTTPS://WWW.NAVCEN.USCG.GOV MILITARY - GPS WARFIGHTER COLLABORATION CELL at HTTPS://GWCC-WS.CCE.AF.MIL/GPSOC, DSN 560-2541, COMM 719-567-2541, gpsoperationscenter@us.af.mil, HTTPS://GWCC-WS.CCE.AF.MIL MILITARY ALTERNATE - JOINT SPACE OPERATIONS CENTER, DSN 276-3526. COMM 805-606-3526. JSPOCCOMBATOPS@US.AF.MIL 2025076------------------------ NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2025076 SUBJ: SVN53 (PRN17) FORECAST OUTAGE SUMMARY JDAY 338/0600 - JDAY 338/1800 1. NANU TYPE: FCSTDV NANU NUMBER: 2025076 NANU DTG: 301732Z NOV 2025 REFERENCE NANU: N/A REF NANU DTG: N/A SVN: 53 PRN: 17 START JDAY: 338 START TIME ZULU: 0600 START CALENDAR DATE: 04 DEC 2025 STOP JDAY: 338 STOP TIME ZULU: 1800 STOP CALENDAR DATE: 04 DEC 2025 2. CONDITION: GPS SATELLITE SVN53 (PRN17) WILL BE UNUSABLE ON JDAY 338 (04 DEC 2025) BEGINNING 0600 ZULU UNTIL JDAY 338 (04 DEC 2025) ENDING 1800 ZULU. 3. POC: CIVILIAN - NAVCEN AT 703-313-5900, HTTPS://WWW.NAVCEN.USCG.GOV MILITARY - GPS WARFIGHTER COLLABORATION CELL at HTTPS://GWCC-WS.CCE.AF.MIL/GPSOC, DSN 560-2541, COMM 719-567-2541, gpsoperationscenter@us.af.mil, HTTPS://GWCC-WS.CCE.AF.MIL MILITARY ALTERNATE - JOINT SPACE OPERATIONS CENTER, DSN 276-3526. COMM 805-606-3526. JSPOCCOMBATOPS@US.AF.MIL 2025077------------------------ NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2025077 NANU TYPE: GENERAL *** GENERAL MESSAGE TO ALL GPS USERS *** This is an amendment to NANU 2025075. OPERATIONAL NOTICE: Testing will be starting no earlier than JDAY 339 (05DEC25) using PRN 34 with the third Navigation Technology Satellite (NTS-3) and is planned to continue through June 2027. GPS users should not attempt to track or use the signals transmitted by NTS-3 since they will not be IS/ICD compliant. TECHNICAL INFORMATION: To mitigate the risk of backward-compatibility issues with GPS user equipment, the NTS-3 PRN34 L1 C/A-code transmissions will include modified Legacy Navigation (LNAV) data comprising alternating 1's and 0's in the message content portion of words 3-10 of subframes 1-5 with proper (32,26) Hamming Code parity bits throughout. The most significant bit (MSB) of the six-bit space vehicle (SV) health indication in subframe 1 will be set to 1, indicating "some or all LNAV data are bad". *** GENERAL MESSAGE TO ALL GPS USERS *** POC: CIVILIAN and MILITARY -- AFRL.RV.NTS3@us.af.mil 2025078------------------------ NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2025078 SUBJ: SVN53 (PRN17) FORECAST OUTAGE SUMMARY JDAY 338/0608 - JDAY 338/1220 1. NANU TYPE: FCSTSUMM NANU NUMBER: 2025078 NANU DTG: 041241Z DEC 2025 REFERENCE NANU: 2025076 REF NANU DTG: 301732Z NOV 2025 SVN: 53 PRN: 17 START JDAY: 338 START TIME ZULU: 0608 START CALENDAR DATE: 04 DEC 2025 STOP JDAY: 338 STOP TIME ZULU: 1220 STOP CALENDAR DATE: 04 DEC 2025 2. CONDITION: GPS SATELLITE SVN53 (PRN17) WAS UNUSABLE ON JDAY 338 (04 DEC 2025) BEGINNING 0608 ZULU UNTIL JDAY 338 (04 DEC 2025) ENDING 1220 ZULU. 3. POC: CIVILIAN - NAVCEN AT 703-313-5900, HTTPS://WWW.NAVCEN.USCG.GOV MILITARY - GPS WARFIGHTER COLLABORATION CELL at HTTPS://GWCC-WS.CCE.AF.MIL/GPSOC, DSN 560-2541, COMM 719-567-2541, gpsoperationscenter@us.af.mil, HTTPS://GWCC-WS.CCE.AF.MIL MILITARY ALTERNATE - JOINT SPACE OPERATIONS CENTER, DSN 276-3526. COMM 805-606-3526. JSPOCCOMBATOPS@US.AF.MIL