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GLOBAL POSITIONING SYSTEM (GPS) WEEK ROLLOVER EVENT

Date Signed: 1/31/2019
MARADMINS Number: 059/19

R 311222Z JAN 19
MARADMIN 059/19
MSGID/GENADMIN, USMTF, 2007/CMC WASHINGTON DC C4 (UC)/F002//
SUBJ/GLOBAL POSITIONING SYSTEM (GPS) WEEK ROLLOVER EVENT//
REF/A/DOC/USNO BRIEF/20170926//
REF/B/DOC/DHS MEMORANDUM FOR U.S. OWNERS AND OPERATORS USING GPS TO OBTAIN UTC TIME; UPCOMING GLOBAL POSITIONING SYSTEM WEEK NUMBER ROLLOVER EVENT/20180410//
NARR/REF A IS A BRIEF FROM UNITED STATES NAVAL OBSERVATORY (USNO) TITLED “GPS WEEK ROLL OVER ISSUE” LOCATED AT HTTPS:(SLASH SLASH)WWW.GPS.GOV(SLASH)CGSIC(SLASH)MEETINGS(SLASH)2017(SLASH)POWERS. PDF.//REF B IS THE HOMELAND SECURITY “MEMORANDUM OF U.S. OWNERS AND OPERATORS USING GPS TO OBTAIN UTC TIME” LOCATED AT HTTPS: (SLASH SLASH)ICS-CERT.US-CERT.GOV (SLASH) MEMORANDUM-US-OWNERS-AND-OPERATORS-USING-GPS-OBTAIN-UTC-TIME//
POC/DAVID VAUGHN/CTR/UNIT: HQMC C4CS/NAME: WASHINGTON DC/TEL: 703-697-5417/EMAIL:DAVID.VAUGHN.CTR@USMC.MIL//
POC/ANDRE COLEMAN/CIV/UNIT: HQMC C4CS/NAME: WASHINGTON DC/TEL: 571-256-8836/EMAIL:ANDRE.COLEMAN@USMC.MIL//
1.  GENTEXT/REMARKS/Purpose.  This MARADMIN advises Marine Corps Global Positioning System (GPS) users about a GPS week number rollover event on 6 April 2019 that may affect GPS receiver operation.
2.  Background. GPS receivers obtain time from the GPS constellation using a 10-bit week number which counts weeks from zero to 1023 and then returns to zero rather than incrementing to 1024.  This may cause some receivers to report a date 1024 weeks (19.6 years) in the past when the week number is zero.  This means that on 6 April 2019, some GPS receivers may report the date as 22 August 1999.  In order to mitigate this issue, GPS manufacturers provide software updates to ensure the zero week is correctly interpreted.
3.  Action. All Marine Corps GPS users should verify that their receivers are running software that will correctly increment the date through the week rollover. Defense Advance GPS Receivers (DAGRs) using operating software versions 984-3006-008 or 811-4960-002 and systems with embedded Ground-Based GPS Receiver Application Module (GB-GRAM) receivers using operating software versions 984-2692-006, 984-2662-005, or 811-2883-004 are expected to be compliant and no further action is necessary. If the software version is different, contact Marine Corps Tactical Systems Support Activity (MCTSSA) Operating Forces Tactical Systems Support Center (OFTSSC) at HTTPS: (SLASH SLASH) MCEITS.USMC.MIL (SLASH) SITES (SLASH) MCTSSA or call Monday through Friday 0730-2330 Local Time at (760)725-0533.  Users operating GPS receivers from other manufacturers should contact the device manufacturer.
4. DAGR software update guide is available at HTTPS:(SLASH SLASH)WWW.PMPNT.ARMY.MIL (SLASH) DAGR-SOFTWARE-UPDATE (SLASH)
5. Release authorized by BGen Lorna M. Mahlock, Director, Command, Control, Communications, and Computers (C4), Washington, D.C.//