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39 degree inclination
Thirty-nine degrees of inclination is chosen for many missions dedicated to life sciences. This orbit allows the crew to minimize sleep shifting (which is done to have a early morning landing opportunity). All other inclinations require sleep shifting of 8 or 9 hours during the flight (see Determination of Launch Time). To achieve a 39 degree orbit, the Shuttle has to launch to the east-north-east from Kennedy Space Center to reach the 39 degree latitude before turning southward. This orbit covers the African, South American continents and Australia, most of the U.S., Southern Europe and most of Asia, and goes as far north as France, Romania, Tibet and Japan.

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