Early Solar and Heliophysical Space Missions

Abstract

The sun is the most important element in the Solar System. Without it life would not exist. When the sun dies in an explosive nova billions of years in the future, this will be the end of existence as now known to humanity. Thus heliophysics, or the understanding of the nuclear fusion processes of the sun and its overall dynamics, has been one of the top priorities for astronomers, astrophysicists, and scientists even before the start of the Space Age. With the ability to put telescopes, gamma and X-ray detectors, spectrometers, coronagraphs, and other sensing instruments into space, there have been a wealth of space projects designed to study the sun and its operation over the past 50 years. There have been missions from NASA, the US Navy and Air Force supported by observatories, research universities, and key research institutes. Further there have been important civilian and military space research missions from France, Germany, Japan, and other countries as well. This chapter seeks to cover in a summary fashion many of the earlier solar and heliophysics research as well as military backed missions. These pioneering efforts have helped to unlock some of the mysteries of the sun’s internal operations and have provided insights that have helped us to design better solar probes for current space experiments and monitoring spacecraft currently studying the sun.

This chapter starts with discussing a number of the solar-related experiments carried out by the Orbiting Solar Observatories, the Solwind (P78-1) Project, and Helios-A and Helios-B that represented the very first solar probes. Next the Skylab experiments carried out by onboard astronaut experimenters are described. This is followed by recapping key elements that come from the following space probes: the Solar Maximum Mission, the Upper Atmosphere Research Satellite (UARS), and the Active Cavity Radiometer Irradiance Monitor (ACRIM) Satellite. Data from these sources have produced significant information on total solar irradiance and how the sun’s power output actually varies about 0.1 % over time. This is followed by information on the Coriolis satellite, the Ulysses satellite, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), Windsat, the Yohkoh satellite (also known as Solar-A) and Hinode (also known as Solar-B), and the Transition Region and Coronal Explorer (TRACE) satellite.