Originally Posted by TOGA LK

The sat antennas and transceivers were likely powered up and despite a lack of commands to transmit data, they still ping the satellites and the satellites ping back. Essentially it's a "hey I am here." The satellite records the asimuth from which the satellite received it's last ping from the aircraft. Of the two satellite systems I know of , Inmarsat and Iridium, one is geosynchronous and the other in orbit. It really makes no difference as the jet is always moving along from one to the next anyways. The ping ensures the connection is maintained from one satellite to the next. That's the .02 version.