Countdown

A countdown is a sequence of backward counting to indicate the time remaining before an event is scheduled to occur. NASA commonly employs the terms 'L-minus' and 'T-minus' during the preparation for and anticipation of a rocket launch, and even 'E-minus' for events that involve spacecraft that are already in space, where the 'T' could stand for 'Test' or 'Time', and the 'E' stands for 'Encounter', as with a comet or some other space object. Other events for which countdowns are commonly used include the detonation of an explosive, the start of a race, the start of the New Year, or any anxiously anticipated event. An early use of a countdown once signaled the start of a Cambridge University rowing race. One of the first known associations with rockets was in the 1929 German science fiction movie Frau im Mond (English: Woman in the Moon) written by Thea von Harbou and directed by Fritz Lang in an attempt to increase the drama of the launch sequence of the story's lunar-bound rocket.Time: T minus 3 minutes. Launch Control (LC): OSM, third stage S&A arm permit to close. OSM: Closed. LC: SSC, third stage S&A armed. SSC: Armed. LC: Prop 1, vehicle fuel tank press open. Prop 1: Open. LC: Fuel umbilical purge to open. Prop 1: Open. LC: SSC, vent 1 heater control exit. SSC: Exit. LC: SSC, vent 2 heater control exit. SSC: Exit. LC: NSC reports spacecraft is go. Mission Director: Kepler spacecraft is go. LC: SSC - FTS bat one and two heater controls heaters off. SSC: Off. LC: Prop 1, pressurized first stage LOX tanks to relief. Prop 1: Pressurized. LC: Prop 2, top first stage LOX to 100 percent levels. Prop 2: Up and down, 100 percent. Time: Ninety seconds. LC: SSC, hydraulic external power to on. SSC: External. Time: Eighty seconds. LC: RCO, report range go for launch. Range Control Officer (RCO): Range go for launch. Mission Director: LC (Viera), you're go for launch. LC: Roger. A countdown is a sequence of backward counting to indicate the time remaining before an event is scheduled to occur. NASA commonly employs the terms 'L-minus' and 'T-minus' during the preparation for and anticipation of a rocket launch, and even 'E-minus' for events that involve spacecraft that are already in space, where the 'T' could stand for 'Test' or 'Time', and the 'E' stands for 'Encounter', as with a comet or some other space object. Other events for which countdowns are commonly used include the detonation of an explosive, the start of a race, the start of the New Year, or any anxiously anticipated event. An early use of a countdown once signaled the start of a Cambridge University rowing race. One of the first known associations with rockets was in the 1929 German science fiction movie Frau im Mond (English: Woman in the Moon) written by Thea von Harbou and directed by Fritz Lang in an attempt to increase the drama of the launch sequence of the story's lunar-bound rocket.