have small control surfaces in their trailing edges to control roll. The upper stage has smaller cropped-deltas near the middle of the airframe, with a smaller set of control surfaces at the extreme rear and (in most models) much smaller fins on the nose. The missiles are guided using radio control signals (sent on one of three channels) from the guidance computers at the site. The earlier S-75 models received their commands via two sets of four small antennas in front of the forward fins while the D model and later models used four much larger strip antennas running between the forward and middle fins. The guidance system at an S-75 site can handle only one target at a time, but it can direct three missiles against it. Additional missiles could be fired against the same target after one or more missiles of the first salvo had completed their run, freeing the radio channel. The missile typically mounts a fragmentation warhead, with proximity, contact, and command fusing. The warhead has a lethal radius of about at lower altitudes, but at higher altitudes the thinner atmosphere allows for a wider radius of up to . The missile itself is accurate to about , which explains why two were typically fired in a salvo. One version, the S-75AK, mounted a nuclear warhead of an estimated 15 kiloton yield or a conventional warhead of similar weight. Typical range for the missile is about , with a maximum altitude around . The radar and guidance system imposed a fairly long short-range cutoff of about , making them fairly safe for engagements at low level. Table of SA-75 / S-75 missiles Radar The S-75 typically uses the P-12 early warning radar (also known by its NATO codename, "Spoon Rest"), which has a range of about . The P-12 provides early detection of incoming aircraft, which are then handed off to the acquisition Fan Song radar. These radars, having a range of about , are used to refine the location, altitude, and speed of the hostile aircraft. The Fan Song system consists of two antennas operating on different frequencies, one providing elevation (altitude) information and the other azimuth (bearing) information. Regimental headquarters also include a Spoon Rest, as well as a Flat Face long-range C-band radar and Side Net height-finder. Information from these radars is sent from the regiment down to the battalion Spoon Rest operators