THOR will be a spinning spacecraft with its spin axis pointed towards the Sun, rotating at 2 rpm. The particle instruments will be mounted on the platform of the spacecraft, and the electromagnetic field measurements will be made with sensors on two solid booms and four long wire booms (for the DC and low-frequency electric field measurements). The Sun-pointing orientation gives several critical advantages: a constant solar illumination of the spacecraft throughout the spin allows high accuracy electric field and satellite potential measurements; it allows high resolution solar wind ion measurements using the Faraday Cup instrument; it allows particle instrument design reducing solar wind UV pollution and solar wind ion saturation effects.

More information on the preliminary spacecraft design by the ESA Concurrent Design Facility (CDF) can be found here