The Solar Orbiter mission has extraordinary characteristics: unlike the majority of spaceships, it will not orbit around the Earth but rather around the Sun, at a distance similar to that of Mercury’s orbit, which will give it a unique vantage point and allow it to observe the solar poles. Its instruments will take local as well as remote measurements which will for the first time yield a comprehensive vision of solar physics as well as of the heliosphere. SO/PHI, co-managed by the Institute of Astrophysics of Andalusia (IAA-CSIC), will be the largest and perhaps most complex instrument on board the spaceship.
The mission, scheduled to be launched in July 2017, will orbit five times around the Sun in the course of two and a half years. “The orbital mechanics which will bring the spaceship in the vicinity of the sun are complex and very beautiful: they are based on successive gravitational pulls from the Earth and Venus, and they will elevate the orbital plane in such a way that we can access the high latitudes of the sun and obtain the first quality view of the magnetic field in its poles”, says Jose Carlos del Toro Iniesta, IAA astronomer and main associated researcher using the SO/PHI instrument.
SO/PHI: THE MAGNETIC FIELD IN DETAIL
The main objective of SO/PHI is to map out precisely the solar magnetic field, which is responsible for practically all phenomena observed on the Sun, such as sunspots, solar storms or solar winds (a continuous flow of electrically charged particles emanating from the Sun and travelling through interplanetary space). SO/PHI will also measure the speed of plasma in the photosphere, the innermost layer of the Sun’s atmosphere and origin of the solar winds.
SO/PHI is the heir of IMaX, an instrument designed in Spain for the SUNRISE mission, and it is the heaviest and most energy consuming instrument on board Solar Orbiter (thirty kilograms and thirty watts). This instrument, which includes two telescopes, was designed for imaging, polarimetry and spectroscopy. “It will do everything that can be done in astronomy with light”, says Del Toro (IAA-CSIC).
Another singularity of SO/PHI is that instead of transmitting primary data, it will do the science on board: a device designed by IAA-CSIC, with a speed equivalent to fifty networked computers, will transform these measures into maps of physical solar magnitudes; the former will be destroyed to liberate memory space and the latter will be sent to Earth.
“Never before has a space instrument worked like this”, says Jose Carlos Del Toro Iniesta (IAA-CSIC). “It implies a risk which is difficult to accept, but it was the only solution. Distance limits the transmission of data to one megabyte per day, and that has to be split between ten instruments. During observation periods SO/PHI will generate about three hundred and twenty gigabytes per minute, so the only way to make the instrument worthwhile was to analyze the information on board”.
SO/PHI is being developed by an international consortium (45% German, 40% Spanish, 10% French and the rest from other countries). Coordinating the Spanish part was the responsibility of the Institute of Astrophysics of Andalusia (IAA-CSIC), in collaboration with the Institute of Astrophysics of the Canary Islands (IAC), the National Institute of Aerospace Technics (INTA), the universities of Valencia and Barcelona, and the Polytechnic University of Madrid.
Concepción artística de la misión (ESA).
SOLAR ORBITER: SCIENTIFIC CONTRIBUTIONS
The solar orbit mission is different from its predecessors in that it will study the entire solar physics and the interplanetary medium: it will observe how the sun influences its environment and what the origin of that influence is. The mission will follow an elliptic orbit around the Sun and, during the window of maximum proximity, will rotate with it, which will permit an unprecedented comprehension of solar structures by combining high resolution and temporal continuity.
Moreover, it will yield the first quality vision of the polar magnetic field, key to understanding the change in magnetic polarity the Sun undergoes every eleven years and whose mechanism is unknown. Finally, the mission will use helioseismology techniques to study what goes on inside the Sun.