[1] Timesharing OPerating System / The OPerating System
[2] Traffic Operator Position System
[3] Teletype Optical Projection System (->"IEEE Standard Dictionary")
[4] Thermölectric Outer Plant Spacecraft (->"IEEE Standard Dictionary")
[5] Towards other Planets (NASA-Rahmenprojekt)
[6] Transistorized Operational Phone System (->"NASA Acronym List")
[7] Technical Office Protocol Standard