GPS Testing Notice Concerning the GPS Week Number Rollover

The Global Positioning System Directorate has released a Federal Register Notice announcing plans to execute a test in February 2019 to investigate legacy receiver week roll-over behavior and analyze any off-nominal behavior exhibited.

The Global Positioning System (GPS) week number rollover occurs in the GPS legacy navigation (LNAV) message every 1024 weeks due to the GPS week number being represented by only 10 bits within the LNAV message. The next GPS week number roll over will occur 18 seconds prior to the 0000Z boundary (Coordinated Universal Time) between April 6/7 2019. In most cases, any negative response from a GPS receiver caused by a problem accounting for the 10-bit week number roll over would likely affect the calendar conversion from GPS time to UTC date/time and could result in the GPS receiver thinking it had jumped backward in time by 1024 weeks to 21/22 August 1999.

If you wish to participate in this test, please submit the answers to the questions in the Federal Register Notice to the SMC/GPE mailbox by February 4, 2019. After the submission of the questionnaire, the team will schedule individual meetings with interested civil vendors to further discuss their participation in the test in more detail.

You will find the full text of the Federal Register Notice and the list of nine questions at