IPY Lighting Field

The required Lighting field defines the day/night lighting conditions required at the time of the photograph. The lighting is defined by the elevation of the sun with respect to the horizon as viewed from a spot on the Earth directly below the space station at the time the photograph is taken. Any angle greater than ten degrees of elevation is considered daylight. Between negative ten and ten is considered twilight. Less than negative ten is considered night.

This selection is used by the "Check Status" page for displaying links to existing images in our database that may apply to the request. It is also used when determining times to put in our messages to the International Space Station crew of when to take pictures.