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Day/Night on the Ground Tracks

The shuttle spends roughly half of its orbit over the night side of the Earth and the other half over the sunlit side. This means that during its 90 minute orbit, 45 minutes of the ground track are in day and 45 minutes are in night. The figure below shows a ground track for one orbit during STS-81. The dotted line of the ground track indicated that the shuttle is in daylight and the solid line signifies that that portion of the orbit is in night. KidSat images are taken of locations on Earth which are in daylight. In this example, images can be taken from 130° West (-130°) to 30° East (+30°) in longitude along the ground track. 

[[image]] Map projection of the earth, displaying the shuttle's orbit through day and night. [[/image]]

Important Facts About STS-81 Ground Tracks:
1) The direction of the shuttle's ground track is from West to East. 
2) The ground track does not go above 51.6° North or below 51.6° South. 
3)The ground track ascending and descending nodes shift 22.5° to the West for each successive orbit. 
4) Approximately one-half of the ground track is in daylight for each orbit. 

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