In plain words no jargon; hover or tap any dotted word for what it means
Reading NOAA…
The satellites over the Earth, now drag to turn, scroll to zoom, click the sea to stand there
Navigation satellites in service
Two readings for each system. The operator is what the system's own status service says is in service. Broadcasting healthy is what the satellites themselves broadcast today: the health flag in each one's navigation message, as received by the IGS network. They usually agree; where they don't, the operator's notice explains why.
The words, in plain English every dotted word above, explained
Where it comes from
Satellites in service are read twice a day from each operator's own status service and from the IGS daily broadcast file. Orbits come from CelesTrak (US Space Force tracking); every position is worked out in your browser for this moment.
What it is not
Not a forecast of your own receiver, and blind to jamming and spoofing: a transmitter near the vessel overrides everything here, however quiet the sky. Satellites in view assume an open sky; masts, cranes and the superstructure hide some. Watch your own receiver and use the official broadcast at sea.
Why it matters at sea
Every position offshore hangs off GNSS and its corrections, and HF is still the backup voice link. A satellite out of service, or too few in view, shows first in the residuals. For what the sun is doing to the signals, see Space Weather.