That means absolutely nothing, unfortunately. I usually see that icon when I'm on the Subway, and I'd be deeply impressed if Globalstar could actually transmit through a few meters of water and a couple more of rock.
The only thing this icon does seem to respect is general geolocation (i.e. I haven't seen it in unsupported countries). You'll only know if you have satellite connectivity if you actually try using it.
The SOS icon means you're off your network, but you can still make emergency 911 calls. The phone will connect to whatever network is available (if any) to make the call. By law (in the U.S.), the other networks have to carry the call free of charge.
I have an iPhone X that's not signed up with any network, and isn't capable of satellite communications, but still displays the SOS icon because it can make 911 calls.
I'm talking about the SOS + satellite icons appearing together. In my experience, that only appears if there is no other network available, which is the case in most subway tunnels in NYC.
The only thing this icon does seem to respect is general geolocation (i.e. I haven't seen it in unsupported countries). You'll only know if you have satellite connectivity if you actually try using it.