(315 kg) and three small atmospheric probes. The large probe was released on November 16, 1978 and the three small probes on November 20. All four probes entered the Venus atmosphere on December 9, followed by the bus. The Pioneer Venus large probe was about 1.5 m in diameter and equipped with 7 science experiments. After deceleration from initial atmospheric entry at about 11.5 km/s, a parachute was deployed at 47 km altitude. The probe stopped broadcasting when it impacted the surface. The science experiments were: a neutral mass spectrometer to measure the atmospheric composition a gas chromatograph to measure the atmospheric composition a solar flux radiometer to measure solar flux penetration in the atmosphere an infrared radiometer to measure distribution of infrared radiation a cloud particle size spectrometer to measure particle size and shape a nephelometer to search for cloud particles temperature, pressure, and acceleration sensors The three small probes were identical to each other, 0.8 m in diameter and 90 kg each small probe. The small probes were each targeted at different parts of the planet; 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. See also 1978 in spaceflight Vega program Venera program References External links NASA: Pioneer Venus Project Information Pioneer Venus Program Page by NASA's Solar System Exploration NSSDC Master Catalog: Spacecraft Pioneer Venus Probe Bus. (Other components of the mission have their own pages at this site too.) Pioneer Venus specifications at NASA "The Pioneer Venus Orbiter: 11 years of data." Results published on May 1, 1990. Art for the mission Missions to Venus Pioneer program 1978 in spaceflight Spacecraft launched in 1978