SEC Secondary SECO S-IVB Engine Cut-off SECS Sequential Events Control System SEP Separate SEQ Sequence S-IVB Saturn IV B(Third Stage) SLA Service Module LM Adapter SLOS Star Line-of-Sight SM Service Module SPOT Spot Meter SPS Service Propulsion System SR Sunrise SRC Sample Return Container SRX S-Band Receiver Mode No. X SS Sunset STX S-Band Transmit Mode No. X S.V. State Vector SWC Solar Wind Composition Sw Switch SXT Sextant T EPHEM Time of Ephemeris Update TA Trunnion Angle TAN Tananarive, Madagascar TB Time Base TCA Time of Closest Approach TD&E Transposition Docking & LM Ejection TEC Trans Earth Coast TEI Transearth Insertion TEMP Temperature TERM Terminate TEX Corpus Christi, Texas TGT Target TIG Time of Ignition TLC Trans Lunar Coast TLI Translunar Insertion TLM or TM Telemetry TPF Terminal Phase Final TPI Terminal Phase Initiation TPM Terminal Phase Midcourse T/R Transmitter/Receiver TRANS Translation TV Television TVC Thrust Vector Control TWR Tower US United States V Velocity VAN USNS Vanguard VHF Very High Frequency VLV Valve VI Inertial Velocity VOX Voice Keying VXX Verb XX W/O Without WRT With Respect to WTN USNS Watertown XFER Transfer XMIT Transmit or Transmitter XPONDER Transponder Y Yaw vii