Mission Elapsed Time
Mission Elapsed Time ( MET short, English for " elapsed mission time " ) refers to a method of time measurement, which originally developed by the U.S. space agency NASA and later also by other organizations ( such as ESA ) is used during space flights.
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The elapsed mission time has been used for example for a space mission of NASA's Space Shuttle Space Shuttle.
At the Consultative Committee for Space Data Systems ( CCSDS ), the MET is enshrined in a Blue Book as the currently applicable standard, in addition to other time formats. Used in traffic but then usually the CUC - time format.
The term replaces the older term Ground Elapsed Time (GET ) from since the beginning of space shuttle flights, to avoid confusion with the then in use GMT ( Greenwich Mean Time).
At the time of lifting (English Liftoff ) a mission MET watches the shuttle as well as the watches of the astronauts are set to zero; time recording then occurs from the moment of starting in normal days, hours, minutes and seconds. 4/ 06: 48:12 MET therefore means, for example, 4 days, 6 hours, 48 minutes and 12 seconds.
The Mission Elapsed Time is used because it allows the planning of experiments and time sequences on board the spaceship can be done regardless of the often short-term changes actual start date of the mission. However, they met there at boundaries where it needs to be synchronized with other time systems. Therefore, the additional use of the CUC and other time formats.
In contrast to temporary space flights, the time is according to Coordinated Universal Time ( UTC) measured in the stable long-term space station ISS.
The mission of Gemini 6 -A played the clock, which measures aboard the MET, a special role. When attempting to start on 12 December 1965, the timer is triggered too early and started to run. When the main computer noticed this error, the engines were switched off again one second after ignition. In this situation, the astronauts would have had to save himself by ejection seat, as the engine shutdown an already started ( loud timer running ) rocket must inevitably cause the rocket to the launch site crashes and explodes back. However, since they did not feel the movement of the rocket, they mistrusted the clock and reported only the switched off engine. This was the start will be made up three days later and the rendezvous maneuvers are performed with Gemini 7.
- Space Physics