All information on this page is taken from the GPS Satellite Outage File and SEM almanacs produced by the US Air Force 2nd Space Operations Squadron, and made available by the US Coast Guard.
Historical outages are colored black, Predicted outages are colored gold, Current outages are colored red
A GPS historical outage table can be accessed from the link below. The historical outages table contains all GPS outages since 1998.
The information below shows the number of healthy GPS satellites, since 1998. The number of satellites in the GPS constellation comes from the SEM almanac for that day. The number of unhealthy satellites for that day comes from the Satellite Outage File. The SOF outages are subtracted from the number of satellites in the constellation to get the number of healthy satellites.
The list of unused PRN numbers come from those PRNs not listed in the SEM almanac.
This graph plots the number of healthy GPS satellites since 1998 (Full History), or over the last 365 days.
Note that since this is calculated on a daily boundary, this graph will show sequential outages in a single day as concurrent, and may not reflect the more updated statistics above.