PHI (Polarimetric and Helioseismic Imager)
PHI is aimed at mapping the vector magnetic field and the line-of-sight velocity of the solar photospheric plasma. It includes two telescopes (a full disk telescope and a high resolution one) to image the Sun, a Fabry-Pérot interferometer to do spectroscopy and liquid-crystal, variable retarders to do polarimetry.
Solar Orbiter will explore internal regions of the Solar System unachievable so far, study the sun form a distance unexplored (0.28 AU) and provide information about solar polar regions (difficult to observe with telescopes situated in the elliptical plane) from high latitudes up to 35º.
Extrapolations of the magnetic field observed by PHI into the Sun’s upper atmosphere and heliosphere will provide the information needed for other optical and in situ instruments to analyze and understand the data recorded by them in a proper physical context.
The IAA is the PHI co-PI institution. The IAA is in charge of supporting MPS as PHI PI institution and also in coordinating the Spanish teams participating in PHI.
In addition to these tasks, the solar Physics Group at IAA is responsible for some important work packages in the instrument as the electronics unit and the harness.
The IAA contributes as well to the scientific preparation and data exploitation. The most important and innovative part of the instrument, as well as the E-Unit core, consists on a device specifically designed to invert the radiative transfer equation that will be on board Solar Orbiter. The main aim is to perform in real time the complicated algorithms needed to translate the polarization state of the sun light spectrum in terms of the magnetic field vector and velocity. This task requires the processing of a huge quantity of data in parallel. This algorithm, developed at IAA, will be implemented in a FPGA.