In Satellite communication, localization is the process of finding the exact location of a MS (Mobile Station). It is similar to the procedure followed in GSM network except for the addition of a new register named SUMR (in addition to HLR and VLR)
SUMR stands for Satellite user mapping register. It stores the current position of satellites and a mapping of each user to the current satellite through which communication with satellite is possible.
When setting up a connection, initially the MS sends a signal which is intercepted by one or several satellites. This signal is then forwarded to a gateway.
Now the gateway fetches the details of the user from his HLR and the VLR.
Now using SUMR, the appropriate satellite to set up communication with the MS is determined and communication is set up.