wrote:
Ali Ghorashi wrote:

What does the following NOTAM mean:

GPS 02/001 GPS PRN 26 OTS WEF 0502082100-0502090900

I know it says "GPS Pseudo Random Noise 26 Out of Service" but what
are its implications? Does it mean that RAIM is not available
during the outage?

Maybe, maybe not

It's not at all intuitive what the effect is on RAIM. You can have one
or more OTS and still have RAIM. Or you can have none OTS and still
lose RAIM (although with a fully healthy constellation, the
availability is damn near 100% these days, with 30 operational birds up
there now).

I guess it depends on where you are.
In Oz, I often see in a TAF a few short-duration
holes in RAIM.
eg.

RAIM GPS RAIM PREDICTION 021401
YSBK
02030824 TIL 02030837
02040820 TIL 02040833
02050816 TIL 02050829
GPS RAIM UNAVBL FOR NPA