Spaceflight
On July 29, 1969, less than a week before closest approach, NASA Jet Propulsion Laboratory lost contact with Mariner 7. The center regained the signal via the backup low-gain antenna and were able to start using the high gain antenna again shortly after Mariner 6's close encounter. It was thought leaking gases from a battery (which later failed) had caused the anomaly. Based on the observations made by Mariner 6, Mariner 7 was reprogrammed in flight to take further observations of areas of interest and actually returned more pictures than Mariner 6, despite the battery's failure.
Closest approach for Mariner 6 occurred July 31, 1969, at 05:19:07 UT at a distance of 3,431 kilometres (2,132 mi) above the martian surface. Closest approach for Mariner 7 occurred August 5, 1969 at 05:00:49 UT at a distance of 3,430 kilometres (2,130 mi) above the martian surface. This was less than half of the distance used by Mariner 4 on the previous US Mars flyby mission.
Both spacecraft are now defunct in heliocentric orbits.
Read more about this topic: Mariner 6 And 7