What are the Kepler “seasons” all about?
Kepler was launched into an Earth-trailing heliocentric orbit of a little longer than a year (372.5 days), and this fact has a number of consequences. First, the spacecraft slowly becomes more distant from Earth. This fact ultimately places a hard limit on the mission lifetime. Second, in order to maintain orientation of the solar array toward the Sun, the satellite must roll on its pointing axis four times a year. Each of these intervals is called a season or quarter. The Project designates four seasons, numbered 0, 1, 2, 3, which repeat each Kepler year. New “quarters” start with the beginning of data collection for each new season and run continuously (1, 2, 3, 4, 5, etc.). The exception to this statement is that the Project has designated the commissioning period, ending on May 12, 2009 as “Quarter 0.” This quarter has no analog in the seasons assignments. To find out the predicted and actual season start dates (which differ from one another by as much as a few days) users may cons
