One of NASA’s most successful planetary missions was assembled from leftover hardware: a Voyager bus and antenna, Galileo computers, Ulysses radio tubes, and a space shuttle auxiliary tank. This episode tells the story of Magellan, born in 1983 from the cancelled VOIR proposal, delayed by the Challenger disaster and the loss of its Centaur-G booster, and finally launched from the shuttle Atlantis in May 1989 on a one-and-a-half-year route to Venus. We explain the tense Star 48B orbital insertion burn, steered by 24 hydrazine thrusters because the craft could not be spin-stabilized.

At Venus, Magellan’s synthetic aperture radar used Doppler shifts to simulate an antenna kilometers long, mapping 98 percent of a surface hidden under sulfuric acid clouds while alternating every 3.26-hour orbit between scanning and beaming data home. The maps revealed pancake domes, 6,000-kilometer lava channels, almost no wind erosion, and so few craters that the entire surface appears to have been resurfaced by catastrophic volcanism less than 800 million years ago. We close with the gravity mapping, the first aerobraking at another planet in 1993, the 1994 windmill experiment, and the probe’s deliberate destruction in the atmosphere on October 13, 1994.

• How scavenging proven flight spares paradoxically made Magellan more reliable
• Why a solid rocket motor is a controlled bomb and how the guidance system kept it on vector
• How synthetic aperture radar turned a 3.7-meter dish into a near-photographic imager
• Why Venus lacks plate tectonics and what a stagnant lid means for global resurfacing
• How aerobraking and the windmill experiment changed the fuel budgets of later Mars and Venus missions