The scientific objectives of the International Solar Polar Mission

Abstract

The International Solar Polar Mission (I. S. P. M. ), originally known as the Out-of-Ecliptic Mission, will be the first spacecraft mission to explore the third dimension of the heliosphere within a few astronomical units of the Sun and to view the Sun over the full range of heliographic latitudes. Its main objectives are to investigate, as a function of solar latitude, the properties of the interplanetary medium and the solar corona. The I. S. P. M. is a two spacecraft venture jointly conducted by E. S. A. and N. A. S. A. The two spacecraft will be injected into elliptical heliocentric orbits approximately at right angles to the ecliptic plane, by using the Jupiter gravity assist method, one northwards and the other southwards. After passing nearly above the poles of the Sun, each spacecraft crosses the ecliptic plane and passes over the other solar pole. The complete mission time from launch, foreseen for February 1983, to the second polar passage is approximately 4⅔ years. This paper summarizes the main scientific objectives of the instruments to be carried on this exploratory mission. It concludes with an outline of the payload, the spacecraft, the trajectory and the mission schedule.