I am asking if it is possible for a satellite station to know an aircraft is "live" even though no data stream is received.
That is, does the system log on then log off, regardless of systems data?
The satellite has internal session management logging what is attached, recently attached and due to expire due to no transmission for a certain period but this info is not generally sent back to a ground station, only data destined for an earth based recipient is sent back down because bandwidth is too expensive. Session length depends on the provider. 2 hrs is the norm, upto 24 hrs with some operators.