Mariner 7, mission to Mars, launched 1969

Mariner 7, the second of twin space probes to Mars, was launched March 27, 1969, about a month after Mariner 6 was launched. 

Less than a week before its closest approach, Jet Propulsion Laboaratory lost contact with Mariner 7 on July 29, but they managed to find a signal using a backup low-gain antenna and then regained use of a high-gain antenna.  Mariner 7 made its closest approach to the Red Planet August 5.  After its pass, it was deactivated in December 1970 and now is in a heliocentric orbit.

Mariner 6, spacecraft to Mars, launched 1969

Mariner 6, one of two probes to explore Mars, launched February 25, 1969.  Mariner 7 launched the following month.  Mariner 6 made its closest approach to Mars on July 31, 1969, less than a week after Apollo 11's mission.  As a consequence, Mariner 6's achievements did not receive the attention it should have.