A NANU (Notice Advisory to NAVSTAR Users) is a message issued jointly by the United States Coast Guard and the GPS Operations Centre. VERIPOS receive these messages and forward them to all vessels on our mailing list.
To be added to (or deleted from) the mailing list, contact the VERIPOS Helpdesk at: firstname.lastname@example.org
NANUs provide updates on the general health of individual satellites in the GPS constellation. They are typically issued three days prior to a change in the operation of a GPS satellite, such as a change in orbit or scheduled on-board equipment maintenance.
It is not normally necessary for the user to take any action as a result of a NANU. The GPS Operations Centre set the status of the GPS satellite to “Unhealthy” prior to making any changes which affect positioning and then set it back to “Healthy” once maintenance is complete. Whilst “Unhealthy”, the satellite is automatically excluded from all calculations.
If the user is engaged in critical operations, especially in an area with poor GPS coverage, they should be aware that the reduced satellite count may result in periods of poor DOPs giving reduced positioning accuracy.