ESA solar stereo mission studies

Abstract

Two solar and heliospheric missions have been recently studied by ESA in the frame of a supporting study given to the Horizon 2000 Plus Survey Committee. The first one, called STEREO, has as its objective the 3D observation of the Sun, from a 1 AU solar orbit. The mission requires several spacecraft with line of sight to the Sun separated by a substantial amount. Several options with up to six spacecraft have been considered. As the payload mass decreases rapidly with the number of spacecraft, a multi spacecraft mission could carry less instrumentation, e.g. no optical telescope. A two spacecraft mission is therefore proposed. This opens the possibility to another Space Agency to contribute with a third spacecraft, which would allow a nearly continuous observation of the solar surface. The second mission studied is a Stereoscopic Solar Corona Probe, a mission into a region near the Sun that has never been investigated before. The probe is equipped with an electric propulsion system. The thruster is fired throughout the whole mission allowing a progressive approach to the Sun in a quasi-spiralling orbit. The stereoscopic observation can be accomplished either by two probes injected at a suitable separation angle, or by one probe approaching the Sun and a contemporary observation of the solar corona by a low Earth orbit spacecraft. The 3D structure of the solar corona could also be reconstructed applying tomographic techniques to the series of images recorded by a coronographic optical imager in various projections during the perihelion passages.