GMT, AC-2 (Atlas 126D and Centaur stage #2) took place five days after President Kennedy's assassination. The redesigned Centaur stage functioned without any problems and performed a single burn to geostationary transfer orbit (GTO) (orbit of 474 x 1586 km, inclination of 30.4° and period of 105.8 minutes), where it remains in 2021. The insulation panels were permanently attached to the stage as the jettison problem had still not been solved. Vibration data proved that the panels would have prematurely detached had they not been bolted down. The ultimate fix to the panel problem added more dry mass to Centaur, further dropping its payload capacity. This Atlas-Centaur 2 launch vehicle was used for performance and structural integrity tests. It carried a payload of 4621 kg and instrumented with 907 kg of sensors, equipment, and telemetry. Third flight The AC-3 flight (Atlas 135D and Centaur #3) was launched on 30 June 1964 at 14:04:22 GMT with a payload of 4815 kg. Atlas performance was close to nominal with the sustainer running slightly LOX-rich for the first 70 seconds of flight and the trajectory being more lofted than expected. Insulation panel and payload shroud jettisons were tested for the first time. Following Centaur staging and engine start, the number two (C-2) engine began to lose roll control. The C-1 engine was able to compensate for a time, but the Centaur eventually lost control and began tumbling. Premature engine shutdown due to propellant starvation occurred at T+496 seconds, and the Centaur impacted in the South Atlantic. Postflight investigation traced the malfunction to a failure of the Centaur-2 engine hydraulic gimbal actuator. Fourth flight The AC-4 flight (Atlas 146D and Centaur #4) was launched on 11 December 1964 at 14:25:02 GMT with a payload of 2993 kg (that carried a mass model of the Surveyor spacecraft). It performed propulsion and stage separation tests, following two scrubbed attempts due to bad weather. The guidance system was operated closed-loop for the first time and an attempt was made to recover the payload shroud, which was equipped with a balloon designed to release green marker dye into the ocean. The shroud was sighted by recovery crews but sank into the ocean and could not be located. The Atlas phase of the flight and the initial phase of Centaur flight were uneventful. The mission went awry when the Centaur could not be restarted due to an ill-conceived design