Solar wind and space weather

The main objective of the Solar Orbiter mission is to observe the so-called space weather, i.e. processes taking place in the solar corona which, due to particle radiation (the “solar wind”), directly influence the Earth's atmosphere. They are responsible for polar lights, but can also massively interfere with satellite communications and air travel, as examples.

Solar Orbiter will have a total of ten instruments on board, six of which serve the purpose of remote sensing – three of those in the VUV and EUV spectral range: the Extreme Ultraviolet Imager (EUI) and the SPICE instrument (Spectral Imaging of the Coronal Environment) as well as an observatory channel of the METIS (Multi Element Telescope for Imaging and Spectroscopy). PTB was already involved early on in the development phase of all three instruments by characterizing individual optical components.

In the final phase of instrument characterization, the EUI's flight model has now been calibrated directly radiometrically using the large vacuum tank that was conceived specially for such purposes at the MLS and by tracing it to cryogenic electrical substitution radiometers as primary detector standards. The final calibration of SPICE, however, was carried out externally by means of sourcebased radiometry using a hollow-cathode discharge source whose calibration had, in turn, been traced to the MLS as a primary radiation standard.

These activities were undertaken in Meanclose cooperation especially with the following scientific institutions responsible for the construction and the operation of the instruments: the Centre Spatial de Liège (CSL, Liège, Belgium), the Max Planck Institute for Solar System Research (MPS, Göttingen, Germany) and the Rutherford Appleton Laboratory (RAL, Harwell, UK). The calibrated instruments are currently receiving final assembly on the spacecraft platform and are being prepared for launch.