High Quality Content by WIKIPEDIA articles! The Manned Space Flight Network (abbreviated MSFN, pronounced "misfin") was a set of tracking stations built to support the American space efforts of Mercury, Gemini, Apollo and Skylab. There were two other space communication networks at this time, the Spacecraft Tracking and Data Acquisition Network (STADAN) for tracking unmanned satellites in low Earth orbit, and the Deep Space Network (DSN) for tracking more distant unmanned missions. After the end of Skylab, the MSFN and STADAN were merged to form the Spaceflight Data Tracking Network (STDN). STDN was in turn replaced by the satellite-based Tracking and Data Relay Satellite System (TDRSS), being used as of 2009.