Pioneer Venus Multiprobe Mission

Thirty-five years ago today — August 8, 1978 — a US mission to Venus, featuring four separate probes, launched from Cape Canaveral on an Atlas Centaur rocket.

(Artist’s conception of one of the probes descending toward the surface of Venus. NASA image.)

The Pioneer Venus Multiprobe Bus carried the four probes on the 123-day journey to Venus. On November 16, the Bus released the Large Probe and on the 20th it released the three small probes, which were designated Day, Night, and North, according to their entry into the Venusian atmosphere.

Two Small Probes entered on the nightside, and one Small Probe and the Large Probe entered on the dayside of the planet. The spacecraft was spin-stabilized. The Large Probe took 1-1/2 h to descend through the atmosphere, while the three smaller probes reached the surface of the planet 75 min after entry…. The Probes stopped transmitting temperature data about 15 km above the surface of Venus, but two Probes survived on the surface and transmitted other data for a matter of seconds to minutes.

The Bus itself acted as a fifth probe, though it was not intended to get near the surface. It

was targeted to enter the Venusian atmosphere at a shallow entry angle and transmit data to Earth until [it] was destroyed by the heat of atmospheric friction during its descent…. [It] ceased transmitting data at an altitude of about 165 km.

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