Pioneer 1-5 Pioneer 6-9 The Venus Orbiter The Venus Multiprobe

Pioneer 1 was the first spacecraft to be launched by NASA and provided information on the radiation belts surrounding the Earth.

Pioneer 2 never made it to space, its launch vehicle failed.

Pioneer 3 discovered a second radiation belt around the Earth.

Pioneer 4 was the first American spacecraft to leave Earth orbit as it passed within 58,983 Km of the moon. It transmitted back information about the moon, but failed to be the first spacecraft to reach the moon, beaten by the Russin craft Luna 1.

Pioneer 5 was designed to provide the first map of the interplanetary magnetic field. The spacecraft functioned for a record 106 days and communicated with Earth from a record distance of 36.2 million Km.

Pioneer 6 was launched on a Thor-Delta launch vehicle on 16 December 1965 into a circular solar orbit with a distance of 0.8 AU from the Sun. (The distance from the Earth to the Sun is 1.0 AU). Last transmission

Pioneer 7 was launched on 17 August 1966 into solar orbit with a mean distance of 1.1 AU from the Sun. Last transmission

Pioneer 8 was launched on 13 December 1967 into solar orbit with a mean distance of 1.1 AU from the Sun. Last transmission

Pioneer 9 was launched on 8 November 1968 into solar orbit with a mean distance of 0.8 AU from the Sun. Last transmission

On 20 May 1978 on an Atlas-Centaur launch vehicle the Orbiter (Pioneer 12) was launched . On 4 December 1978, the orbiter was injected into a highly elliptical orbit around Venus usin a solid-propellant rocket motor with 18,000 N of thrust. The lowest orbital point (periapsis), of the Venus orbit was about 150 km above the surface of the planet. The highest orbital point (apoapsis), was 66,000 km from the planet. The orbital period was 23 hours 11 minutes.

In this orbit global mapping of the clouds, atmosphere and ionosphere; measurement of upper atmosphere, ionosphere, and solar wind-ionosphere interaction; and mapping of the planet's surface by radar was performed. In the first 19 months of the mission the lowest orbital point (periapsis) was maintained at 150 km above the surface with periodic maneuvers. These maneuvers which maintained this orbit was discontinued as propellant began to run low, causing the periapsis to rise to about 2,300 km due to Solar gravitational effects. By 1986, the gravitational effects caused the periapsis to start falling again, and the orbiter instruments could again make direct measurement within the main ionosphere.

During the orbiters mission systematic observations was made of several comets using the Ultraviolet Spectrometer (OUVS). Here you see listed the comets and the date of observation:
Encke April 13 through April 16, 1984
Giacobini-Zinner September 8 through 15 1985
Halley December 27, 1985 to March 9, 1986
Wilson March 13 to May 2, 1987
NTT April 8, 1987
McNaught November 19 through 24, 1987.
The results showed for Halley that, near perihelion (when comet is at its nearest to the sun), the water evaporation rate was about 40 tonnes per second.

Starting in September 1992, controllers used the remaining fuel on the spacecraft in a series of maneuvers to keep raising periapsis altitude for as long as possible. On 8 October 1992, its fuel supply was exhausted. Not long after the fuel supply was gone the Orbiter ended its mission as a meteor flaming through the dense atmosphere of Venus, after a 14 year long mission.

On 8 August 1978, less than three months after the Venus Orbiter left Earth, the Multiprobe spacecraft (Pioneer 13) was launched from the Kennedy Space Center on an Atlas-Centaur launch vehicle. Only three months later on 16 November 1978, the Large Probe was released from the Bus toward an entry near the equator on the day side of Venus. Four days later, on 20 November 1978, the three Small Probes were released from the bus. Two of the probes were targeted to enter on the night side and one was targeted to enter on the Venus day side. On 9 December 1978 the bus with its instruments was retargeted to enter Venus' day side.

When the probes separated from the Multiprobe bus, they were turned off because they did not have sufficient on-board power and they did not have solar cells to replenish their batteries. Preprogrammed instructions were wired into them and their timers had been set before they separated from the bus. The on-board countdowm timers were scheduled to bring each probe into operation again three hours before the probes began their descent through the Venus atmosphere, this way they had enough power to operate in the descent. On 9 December 1978, just 22 minutes before entry, the Large Probe was turned on by the timer and began to transmit radio signals to Earth. Only 17 minutes before hurtling into the Venusian atmosphere at almost 42,000 km/hr, all the Small Probes started transmitting.

All off the four probes were designed for a descent time of approximately 55 minutes before impacting the surface. None were designed to withstand the impact. However the small Day Probe did survive and sent data from the surface for 67 minutes. Data radioed back from the Day Probe showed that its internal temperature climbed steadily to a high of 126 degrees C. Now its batteries were depleted, and its radio became silent.