The Earth Radiation Budget Satellite (ERBS), launched October 1984 from the Space Shuttle Challenger, was designed to be a 2-year mission to gather required radiation budget data, aerosol data, and ozone data to assess climate change and ozone depletion.  The two experiments conducted were the Earth Radiation Budget Experiment (ERBE) and the Stratospheric Aerosol and Gas Experiment II (SAGE II).  The ERBS spacecraft structure was composed of three basic modules: the keel module, the base module, and the instrument module. The keel module was a torque-box structure providing structural support for the propulsion system, the solar array panels, and the antennas. The base module was a torque-box structure that provided a direct interface to the Shuttle. The ERBE-nonscanning instrument and electronics was attached to the base module. The instrument module was mounted directly to the base module and housed the ERBE-scanner and the SAGE II instrument. Other ERBS subsystems included the Thermal Control Subsystem (TCS) for regulating heat dissipitation; the Electrical Power Subsystem (EPS) which consisted of two 50-amp-hour, 22-cell nickel cadmium batteries; the Power Control Unit (PCU) for regulating electrical power; the Command and Data Handling Subsystem (C&DH) for collection of instrument and spacecraft data for real-time transmission; the Communications Subsystem (CS), which included NASA TDRSS transponders and antennas; the Attitude Control and Determination Subsystem (AC&DS), a three-axis, momentum system for attitude pointing, maneuvers, and thruster control; and the Orbit Adjust Propulsion System (OAPS), a nonpropellent hydrazine propulsion system used for raising the ERBS to its operating orbit after launch from the Shuttle. The ERBS was held primarily in the Earth-pointing mode for most of the mission.