sentences:  The NASA Manned Space Flight Network (MSFN) was a worldwide network of stations that tracked the Mercury, Gemini, Apollo and Skylab missions.Most MSFN stations were only needed during the launch, Earth orbit and landing phases of the lunar missions, but three "deep space" sites with larger antennas provided continuous coverage during the trans-lunar, trans-Earth and lunar mission phases.Today, these three sites form the NASA Deep Space Network