thumb|Arrival of the Pioneer Venus spacecraft at Venus
The Pioneer Venus project was part of the Pioneer program consisting of two spacecraft, the Pioneer Venus Orbiter and the Pioneer Venus Multiprobe, launched to Venus in 1978. The program was managed by NASA's Ames Research Center.
The Pioneer Venus Orbiter entered orbit around Venus on December 4, 1978, and performed observations to characterize the atmosphere and surface of Venus. It continued to transmit data until October 1992. The Pioneer Venus Orbiter was inserted into an elliptical orbit around Venus on December 4, 1978. It carried 17 experiments (with a total mass of 45 kg): They had no parachutes and the aeroshells did not separate from the probe. Two of the small probes reached the surface, and one of these, the day probe, continued to broadcast for 67 minutes and 37 seconds after reaching the surface.
The Pioneer Venus bus also carried two experiments, a neutral mass spectrometer and an ion mass spectrometer to study the composition of the atmosphere. With no heat shield or parachute, the bus made measurements only to about 110 km altitude before burning up.