Mariner 5, Venus probe, launched 1967

Mariner 5, launched June 14, 1967, carried a cadre of instruments to Venus, to study its atmosphere and magnetic field fluctuations above the planet. It had been built as a backup to Mariner 4, a Mars probe, but the Mariner 4 project was a success, NASA modified Mariner 5 to study Venus during the 1967 Venus launch window.

Mariner 5 flew by Venus on October 19, 1967 at an altitude of 2480 miles, and determined that the surface was hotter and the atmosphere denser than previous studies had indicated. 

Between April and November 1968, NASA tried to contact Mariner 5 to reacquire a signal for probing interplanetary conditions.  A signal was received in October, but the they had no success in gaining an uplink signal, so there was no possibility of fixing or continuing its use.  Operations were terminated November 5, 1968.  Mariner 5 remains in a heliocentric orbit.

Mariner 5 flies by Venus 1967

Mariner 5, launched June 14, 1967, made its closest approach to Venus on October 19, 1967.  It was meant to be a backup for Mariner 4, but with the success of that mission,  it was modified for a Venus mission. 

Liftoff went without many problems and data sent during its flyby corroborated the Soviet's Venera 4 lander which arrived at Venus the day before, that the Venusian atmosphere was hotter and more denser than previously thought.

NASA discovered earlier Mariner 5 was in a slow roll and soon after its flyby, contact was lost.  The mission was ended November 5 and the defunct spacecraft is in a heliocentric orbit.