Ground Command Interface Logic

The ground command interface logic, also referred to as the ground command interface logic controller, controls many of the functions of the S-band PM, S-band FM, Ku-band, payload communication and CCTV systems. Commands are sent to the orbiter from the ground through S-band system uplink or Ku-band system forward link. All commands, whether sent on S-band or Ku-band, are routed to the onboard GPC through the NSP and associated MDM. The GCIL takes commands for these systems from the GPCs for ground commands or from the appropriate panel for flight crew commands. The command source is selected at a control panel pnl/cmd switch for each system. If the switch for that system is on pnl, the flight system is in control. If the switch for that system is on cmd, the ground has control.