Mariner 6 and 7

As part of NASA's wider Mariner program, Mariner 6 and Mariner 7 (Mariner Mars 69A and Mariner Mars 69B) completed the first dual mission to Mars in 1969. Mariner 6 was launched from Launch Complex 36B at Cape Kennedy and Mariner 7 from Launch Complex 36A at Cape Kennedy. The craft flew over the equator and south polar regions, analyzing the atmosphere and the surface with remote sensors, and recording and relaying hundreds of pictures. The mission's goals were to study the surface and atmosphere of Mars during close flybys, in order to establish the basis for future investigations, particularly those relevant to the search for extraterrestrial life, and to demonstrate and develop technologies required for future Mars missions. Mariner 6 also had the objective of providing experience and data which would be useful in programming the Mariner 7 encounter five days later.

Launch

Mariner 6 lifted from LC-36B at Cape Kennedy on February 25, 1969 using Atlas-Centaur AC-20 and Mariner 7, from LC-36A on March 27, using AC-19. The boost phase for both spacecraft went according to plan and no serious anomalies occurred with either launch vehicle. A minor LOX leak froze some telemetry probes in AC-20 which registered as a drop in sustainer engine fuel pressure, however the engine performed normally through powered flight. In addition, BECO occurred a few seconds early due to a faulty cutoff switch, resulting in longer than intended burn time of the sustainer engine and Centaur, but this had no serious effect on vehicle performance or the flight path. AC-20 was launched at a 180-degree azimuth which would have resulted in the Atlas passing over part of the Caribbean and South America; to avoid this, the guidance computer was programmed to execute a "dog-leg" maneuver and pull the booster away from land.