Rationale for NASA Planetary Exploration Program

The Planetary Mission Model, NASA's program of future solar system exploration for the years 1973-1990, is presented. The model is based on a continuation of the balanced exploration philosophy, tempered by a conception of the realities of technology availability and fiscal constraints. It envisions the continued use of existing spacecraft technology (i.e., Mariner, Viking, and Pioneer) with only evolutionary changes, but with the introduction of atmospheric probe technology in the late 70's. The Titan/Centaur vehicle would be in use through 1980, and solar-electric propulsion (SEP) capability would be introduced in about 1979. Beyond 1980, shuttle capability is assumed. A brief explanation of the rationale behind the sequences at the following targets is presented: Mercury, Venus, Mars, the outer planets, and comets and asteroids.