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For help on how to understand and/or interpret an Operational Advisory message, please visit our tutorial page.

Format of the messages

Almanacs, Operational Advisories,  and NANUs are available for download in two formats:

  1. the original format in which the files are produced (.alm, .al3., .nnu, and .oa1)
  2. plain text (txt)

OPS Advisories (GPS Status)

  • Current Operational Advisories - .oa1, .txt

Almanacs (YUMA & SEM)



You may need to change the health settings when you use YUMA or SEM almanac data. While the orbital description data is generally usable for months, the satellite health may change at any time. For information on satellite health at times other than the almanac "Time Of Applicability", see the NANUs or status messages. An almanac entry of 000 indicates the satellite is healthy.

In order to aid customers that need to download the various almanac files on a regular or semi-regular basis or who would like to download some or all of the files for one or more years, we have developed a set of access points to allow the download of the files programmatically. Please read the instructions for programmatically downloading NANU, Almanac and Ops Advisory files.