| NANU
ABBREVIATIONS & DESCRIPTIONS
NANU (Notice Advisory to Navstar Users)
A NANU is an advisory message to inform users of a change in the
GPS constellation. These messages are released 72 hours in advance
for planned maintenance. These messages are also used to notify
users of unscheduled outages. General NANUs can be used to disseminate
general GPS information.
Forecast Outages
FCSTDV, or Forecast Delta-V - gives scheduled outage times for
Delta-V maneuvers. The satellite is moved during this maintenance
and the user may be required to download a new almanac.
FCSTMX, or Forecast Maintenance - gives scheduled outage times
for Ion Pump Operations or software tests.
FCSTEXTD, or Forecast Extension - extends the scheduled outage
time "Until Further Notice"; references the original NANU.
FCSTSUMM, or Forecast Summary - gives the exact outage times for
the scheduled outage, including the FCSTEXTD; sent after the maintenance
is complete and the satellite is set healthy to users; references
the original NANU.
FCSTCANC, or Forecast Cancellation -.cancels a scheduled outage;
new maintenance time not yet determined; references the original
NANU.
FCSTRESCD, or Forecast Rescheduled - reschedules a scheduled outage;
references the original NANU
Unscheduled Outages
UNUSUFN, or Unusable Until Further Notice - notifies users that
a satellite will be Unusable to all users until further notice.
UNUSABLE, or UNUSABLE with a reference NANU - closes out an UNUSUFN
NANU and gives the exact outage times for the outage; references
the UNUSUFN NANU.
UNUNOREF, or UNUSABLE with no reference NANU - gives times for
outages that were resolved before a UNUSUFN NANU could be sent.
Other
USABINIT, or Initially Usable, notifies users that a satellite
is set healthy for the first time.
LEAPSEC, or Leap Second, is used to notify users of an impending
Leap Second.
GENERAL, informs the user of general GPS information.
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