Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The energy balance of the solar energy reaching Earth must be studied to verify that the amount of energy coming in equals the amount being radiated out. This is called radiative balance and conforms to the Law of Conservation of Energy. To validate this theory, several satellites have been launched into Earth''s orbit that indirectly measure the energy absorbed and radiated by Earth, and by inference the energy stored. The NASA Earth Radiation Budget Experiment (ERBE) project involves three such satellites: the Earth Radiation Budget Satellite (ERBS), launched October 1984; NOAA-9, launched December 1984; and NOAA-10, launched September 1986.