Orbit selection for the 1978 Pioneer Venus mission

The Pioneer Venus Orbiter will be launched by NASA in the spring of 1978. Selection of the orbit in July, 1975, resulted from scientific, mission, spacecraft, and operational considerations summarized by this paper. The orbit will be inclined 105 deg to the ecliptic, and its periapsis will lie between 16 and 28 deg north celestial latitude. Its periapsis altitude will be maintained between 150 and 260 km above the solid surface, and its period will be kept near 24 hr. This orbit and the spinning spacecraft's ecliptic-normal attitude permit the scientific coverage geometry of Venus, which also is summarized here.