News	back to news index

IMPORTANT NOTICE FROM INMARSAT:
All ships – Potential issues with older GPS equipment

Inmarsat has been made aware that there may be two potential issues with ship’s equipment that receives an input from older GPS receivers (either integral or external input).

1. The maximum possible duration of the date data – day/month/year (format may differ) – from the GPS is 19.6 years, after which the date will roll-over to the original start date of that GPS chip-set. After the roll-over, the actual date displayed will be incorrect. The time display and output will not be affected, and the positioning function should operate normally, though may temporarily be interrupted, taking a longer time or fail to fix the position after the date rolls over.

2. Additionally, the U.S. military has announced that GPS satellite SVN23 is now transmitting L-band code as PRN32 (pseudo-random noise) that may not be recognised by older GPS receivers. Each GPS satellite broadcasts a signal that has an embedded PRN code for receiver processing and some GPS receivers initially are able to accommodate only satellite signals 0-31. Therefore, PRN with number 32 cannot be tracked by some manufacturers' GPSs that can recognise only PRNs numbered 0 through 31.

Both phenomena can potentially affect ship’s communications and/or navigation equipment in terms of incorrect generation and display of some data and ships should check with manufacturers or service representatives for communications and/or navigation equipment on board that may rely on GPS feeds from older GPS chip-sets, to see if the GPS roll-over and/or PRN32 signal may affect operation of the relevant equipment.