Editing Mariner 8 (section)

==Mission==

Mariner 8 was launched on an [[Atlas-Centaur]] SLV-3C booster (AC-24). The main Centaur engine was ignited 265 seconds after launch, but the upper stage began to oscillate in pitch and tumbled out of control. The Centaur stage shut down 365 seconds after launch due to starvation caused by the tumbling. The Centaur and spacecraft payload separated and re-entered the Earth's atmosphere approximately {{convert|1500|km}} downrange and fell into the Atlantic Ocean about {{convert|560|km}} north of Puerto Rico.

A guidance system failure was suspected as the culprit, but JPL navigation chief Bill O'Neil dismissed the idea that the entire guidance system had failed. He argued that an autopilot malfunction had occurred since the event had occurred at the exact moment when the system was supposed to activate. Investigation proceeded quickly and the problem was soon discovered to be the result of a malfunction in the pitch rate gyro amplifier. A diode intended to protect the system from transient voltages was thought to have been damaged during repairs/installation of the pitch amplifier's printed circuit board, something that would not have been detected through bench tests.

{{As of|2024}}, Mariner 8 is the most recent US planetary probe to be lost in a launch vehicle malfunction.