model M-1. The Centaur's ullage motors failed again because they did not have enough propellant for the mission. It decayed on 5 May 1966. Seven Surveyor probes were launched, all on Atlas-Centaur. Beginning with AC-13 (Surveyor 5), Atlas-Centaur vehicles switched to the standardized SLV-3 Atlas core. Operational launches Initially, a modified Atlas D designated LV-3C was used as the first stage. This was quickly replaced by SLV-3C, and later the SLV-3D, both derived from the standard Atlas SLV-3 rocket. Two spaceflights, with the Pioneer 10 and Pioneer 11 space probes to Jupiter, Saturn and exiting the Solar System, used a spin-stabilized "Star-37E" solid propellant final stage weighing 2473 pounds and contributing 8000 mph to the velocities of the spacecraft. With the retirement of the Agena stage in 1978, all Atlas flown from that point onward were paired with Centaurs except for a few military flights involving decommissioned Atlas E/F missiles. Originally designed and built by the Convair Division of General Dynamics in San Diego, California, production of Atlas-Centaur at Convair ended in 1995 but was resumed at Lockheed Martin in Colorado. The list of Atlas-Centaur ID numbers began with AC-1 launched on 8 May 1962 and ended with the last Atlas III (Centaur), AC-206, launched on 3 February 2005. The Rocketdyne-powered Atlas-Centaur was sometimes referred to as a 2½ stage launch vehicle because the Atlas first stage (in most cases) jettisoned the twin-thrust-chamber booster engine prior to the completion of the first stage burn. Atlas-Centaur with a Rocketdyne-powered first stage was used for 167 launches between 1962 and 2004 by which time they had been superseded by Atlas V with a new first stage powered by a much more powerful Russian-designed and built RD-180 twin-chamber engine. (Atlas V is not generally referred to as "Atlas-Centaur" and does not share the AC- serial numbers of the original Atlas-Centaur that had the pressure stabilized first stages.) AC-33 failure On 20 February 1975, AC-33 launched carrying the Intelsat IV F-6 communications satellite. The flight went entirely according to plan up until BECO at T+140 seconds. During booster separation, a swivel lanyard designed to pull out an electrical plug supplying power to the booster section failed to detach, causing a voltage spike that reset the Atlas's guidance computer. The booster drifted off its flight path as a result. SECO was affected on time at T+401 seconds followed by Centaur separation and engine start, but