— ESA (@esa) October 2, 2017
The European Space Agency (ESA) tweeted a spectacular’s artist’s impression of its Solar Orbiter in front of a stormy Sun today. Based on an image taken by NASA’s Solar Dynamics Observatory, it captures the beginning of a solar eruption. The actual eruption took place on 7 June 2011. On the lower right, dark filaments of plasma are arcing away from the Sun. In 2011, the plasma lifted off, before raining back down, creating ‘hot spots’ that glowed in ultraviolet light.
Center stage in the impression, however, is the Solar Orbiter. Inheriting technology from previous missions, the Solar Orbiter is a 3-axis stabilised platform with dedicated heat shield, which is to provide protection from the high levels of solar flux near perihelion.
“Solar Orbiter’s over-arching mission goals are to examine how the Sun creates and controls the heliosphere, the extended atmosphere of the Sun in which we reside, and the effects of solar activity on it. The spacecraft will combine in situ and remote sensing observations close to the Sun to gain new information about solar activity and how eruptions produce energetic particles, what drives the solar wind and the coronal magnetic field, and how the Sun’s internal dynamo works.“
Its solar arrays can be rotated about their longitudinal axis, in order to avoid overheating. A battery pack provides supplementary power at necessary points in the mission, such as eclipse periods encountered during planetary flybys. The Telemetry, Tracking and Command Subsystem will provide a communication link capability with Earth in X-band, with the subsystem capable of handling telemetry, telecommand and ranging simultaneously.
Low-Gain Antennas will be used for launch and early in the mission, and are available as back-up later. The Medium- and High-Gain Antennas used later in the mission are steerable, due to the need to point to a wide range of positions. This is necessary to achieve a link with the ground station and send down sufficient volumes of data. They must also cope with a high thermal load, as well as be able to avoid a build-up of electrostatic energy. The High-Temperature High-Gain Antenna can be folded in, so the Orbiter’s heat shield can protect it. Due to the mission’s unique orbit, the throughput of the data downlink is highly variable. Most data will therefore initially be stored in an onboard memory system and sent back to Earth at the earliest possible opportunity.
The planned orbit so close to the sun will allow for observations of solar surface features and their connection to the heliosphere for much longer periods than from an Earth-orbit. According to ESA:
“The view of the solar poles will help us to understand how dynamo processes generate the Sun’s magnetic field. (…) Since the orbital characteristics will change in the course of the mission, individual orbits will be dedicated to specific science questions. Solar Orbiter is an ESA-led mission with strong NASA participation. There will be ten instruments on board, eight of which will be provided by Principal Investigators through national funding by ESA Member States. A European-led consortium supported by national funding and ESA contributions will provide one complete instrument, whilst the remaining instrument and an additional sensor will be provided by NASA.“
The scientific instruments are in the final stages of being added to the spacecraft. Extensive tests will be conducted in preparation for its planned launch in February 2019 from Cape Canaveral in the United States.