STS 30, 34 And 44- A Rebirth Of The Planetary Missions

No American planetary probe has been launched since the twin Voyager spacecraft in 1979- However, within eighteen months beginning in April 1989, three interplanetary probes will be shot into deep space from Shuttle cargo bays using the Inertial Upper Stage (IUS) as an upper stage booster. In 1986 NASA made the decision to cancel the use of Centaur as an upper stage for the Space Shuttle. This action was one of the results of the tragic Challenger accident in January 1986. With increased safety concerns, it was decided not to risk using cryogenic propellant in the Shuttles payload bay. As a result of that decision a search for a new upper stage to launch the three planetary spacecraft, stranded without a launch system, began. This paper briefly describes the search for a new upper stage and the resulting decisions, but focuses primarily on the methods the selected IUS will fly those missions and what they mean in terms of scientific knowledge to all of us. The first of the three planetary missions to be launched by the Space Shuttle and IUS is the Magellan mission (presently scheduled on STS 30 for April 27, 1989). Upon arrival at the planet Venus 15 months after launch, the spacecraft will use its own solid rocket motor to achieve an elliptical polar orbit and then map the carbon dioxide and sulfuric acid cloud obscured planet surface with its Synthetic Aperture Radar (SAR)