What constellation is backup _ What constellation is backup software?

The gps satellite constellation is configured with several satellites in orbit.

24. The GPS satellite constellation consists of 2/kloc-0 working satellites and 3 in-orbit backup satellites, with a total of 24 satellites. These satellites are evenly distributed on six orbital planes, and there are four satellites working on each plane, one of which is a backup satellite. The system can support 30 to 32 satellites in orbit.