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Section 4.5.
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Terrestrial Time Zones used by Lunar Crews

You're probably aware that once a Space Shuttle clears the tower, NASA reports mission timelines in Central U.S. time; in other words: Houston time. (Zone -5.)

Obviously, this makes like easier for the astronauts (who live here in Houston) as well as for the several hundred people who support the missions on the ground. They have enough to think about without having to calculate time zone changes in their head.

What you might not know is that all our engineering data are tagged to UCT, even the test runs in the laboratories and the water tanks. The time tags are even corrected to Ground Elapsed Time. During a long space mission we can accumulate enough errors due to relativity that it would really mess up the computers. The computers are happiest if they can stay in synch within the boudaries of a single simulation frame -- 25 milliseconds -- and become rather petulant when they can't agree on what time it is.

Back to what time the crew will keep: I suspect that they'll be in whatever time zone is most convenient for the key mission events. The flight to the moon on a typical Apollo trajectory has an unfortunate interval between launch and lunor orbit initiation. You either have the crew awake in the middle of the night, according to their circadian rhythms, or you have them trying to get to sleep after a 19-hour day.

Neither of these is a very good solution for a mission where single blunder can result in disaster; so if anyone has any good ideas, please let us know. The reference mission timeline contains a breakdown of the critical events between launch and landing.

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