Mission to the sun: The solar pioneer

Abstract

The Solar Pioneer is a mission concept developed by the Johns Hopkins University Applied Physics Laboratory (JHU/APL) to do exploratory science in the inner heliosphere and outer solar corona. The concept is derived from the Near Earth Asteroid Rendezvous (NEAR) spacecraft now being built by JHU/APL for NASA. The purpose of the Solar Pioneer is to deliver a payload of scientific instruments to approximately 4 solar radii (Rs - 3 radii above the visible solar surface or photosphere).The Solar Probe concept has evolved since its original introduction to the scientific community in 19781 while the key science questions to be answered have changed little. The primary purpose, to conduct an exploratory in situ basic science investigation, has been focused to emphasize in situ particles and fields measurements of the outer solar corona and inner solar wind region. Key science goals of the probe mission include the determination of:(1)how the solar wind is heated and accelerated,(2)where different types of solar wind come from,(3)how solar energetic particles (SEP) are accelerated, and(4)the nature of the unique plasma turbulence near the sun.The basic characteristics of the JHU/APL baseline concept provide for delivery of 42 to 60 kg of scientific payload to 4 Rs while maintaining a high data rate of 30 kilobits per second (kbps) at 1 astronomical unit (AU) (X-band downlink to 70 meter antenna of the Deep Space Network). The baseline design draws upon the NEAR spacecraft and subsystem design to the maximum extent possible. The baselined launch vehicle is an Atlas IIA with a Star48 insertion stage system. Life-cycle cost control is obtained by:(1)focusing on prime science objectives,(2)applying advanced technology where it makes sense, and(3)capitalizing on developed subsystems derived from the NEAR spacecraftThe Solar Pioneer is designed to solve questions of basic physics about the solar environment, enabling the solution to applied questions of the effects of the sun and solar cycle on the Earth and human society. By implementing a focused strategy from science goals through all stages of program management, such a mission can be carried out for less than one quarter of previous Solar Probe mission cost estimates2,3