The SIDE is one of the experiments for the Apollo Lunar Surface Experiments Package (ALSEP). It is designed to measure mass, energy per unit charge, and flux of positive ions at the surface of the moon. The SIDE contains two analyzers. One is for low energy ions; it consists of E X B velocity analyzer and a cylindrical curved plate energy analyzer aligned with a channeltron electron multiplier. The other is for high energy ions; it consists of a curved plate analyzer only. The combination of energy and velocity data provides both energy and mass analysis of the low energy ions. The high energy ions are energy analyzed only. Each element of the analyzers is discussed separately according to ion trajectories, passbands, and design characteristics. The calibration procedures are described, sample curves given, and results presented.