Solar Orbiter

Artists view of the 'Solar Orbiter' spacecraft encountering the Sun's inner heliosphere.

The Solar Orbiter is an ESA mission for the observation of the Sun with high spatial resolution and for in-situ measurements of the heliosphere very close to the Sun. The Orbiter approaches the Sun in an eccentric orbit as close as 60 solar radii (0.28 AU), where no other space probe has been before. Beside that SOlarOrbiter will for the first time allow to investigate directly the Solar polar region.

The instrumentation is divided into an in-situ and a remote sensing package, whereby the participation of the Kiepenheuer Institute will concentrate on the latter. This consists of a magneto-filtergraph in the visible light (Photospheric and Helioseismic Imager PHI) for the investigation of the photosphere, as well as an EUV spectrograph and filtergraph for investigating the corona. 

The mission is essentially divided into two phases. In the first phase, during the initial orbits, the orbital speed of the space probe in the perihelion will roughly correspond to that of the Sun's rotation so that the probe will "hover" over the same area on the Sun for roughly ten days. As a result, it will be possible for the first time to follow a structure or a process, e.g., the development of the magnetic field of a sunspot from the same angle over a long period. In addition, during this phase particles originating from the source region being observed will be registered with the in-situ instruments.

In the second phase of the mission increasingly higher heliographic latitudes of up to almost 35° will be reached. This permits a detailed view of the magnetic field structure in the photosphere at the poles of the Sun. For the first time, it will be possible to investigate directly the fast solar wind out of the polar coronal holes in the EUV range.

The ESA project web page is located at

In February 2010, the program committee (SPC) of ESA selected Solar Orbiter and two other mission for Phase B. In October 2011 Solar Orbiter was finally selected as the first medium-class mission of the Cosmic Vison 2015-2015 programme. Launch is foreseen for 2017. Nominal science operations will start after about three years of cruise phase.


Participation of KIS:

Together with the  Max-Planck-Institut für Sonnensystemforschung (MPS) and the Instituto de Astrofísica de Canarias (IAC), the Kiepenheuer Institute had worked out a feasibility study for the Photospheric and Helioseismic Imager PHI (then named VIM) that became the baseline for the instrument payload definition.

PHI is being developed by an international consortium led by the MPS.

PHI consists of two telescopes and a filter spectro-polarimeter to meaure the photospheric magnetic field and material flows on the sun with high precision. The Full-DiskTelescope (FDT) observes the solar disk at low spatial resolution, while the High-Resolution Telescope (HRT) has an aperture of 14 cm and observes a  field of view of 1000 x 1000 arcsec^2 with an angular resolution of 1 arcsec. At perihelion this corresponds to a field of 200 Mm x 200 Mm and a spatial resolution of 200 km on the Sun. In order to achieve the polarimetric precision laid down in the science requirements, the HRT is equipped with an Image Stabilization Unit (ISS) that reduces image jitter by a factor of at least 30 for frequencies below 5 Hz, and by a factor of at least 10 for frequencies between 5 and 10 Hz. Under normal conditions, the residual jitter be be around 0.1 arcsec.

KIS leads the development of the ISS, with the University of Barcelona and the Instituto de Astrofisica de Andalucia as partners.

More information about PHI can be found at

Beside the instrumental contribution scientist from KIS will actively participate in the analysis of the scientific data.