The Spectrometer Telescope for Imaging X-rays STIX on Solar Orbiter

The Spectrometer Telescope for Imaging X-rays (STIX) will provide imaging spectroscopy of solar thermal and non-thermal X-ray emissions from ~4 to 150 keV. STIX will play an important role in answering two of Solar Orbiter's main science questions: (1) How and where are energetic particles accelerated at the Sun, and how are they transported into interplanetary space? X-ray images and spectra will provide information on the location, spectrum and intensity of flare accelerated electrons near the Sun. (2) What is the magnetic connection from Solar Orbiter back to the Sun? STIX will play a key role in linking remote sensing and in-situ observations on Solar Orbiter. Radio signatures of flare accelerated electrons will be observed by the Radio and Plasma wave instrument (RPW), while the SupraThermal Electron sensor (STE) of the Energetic Particle Detector suite (EPD) will detect electrons in-situ. Thus, the magnetic structure, field line length and connectivity can be tracked. STIX is based on a Fourier-transform imaging technique similar to that used successfully by the Hard X-ray Telescope (HXT) on the Japanese Yohkoh mission, and related to that used for the Reuven Ramaty High Energy Solar Spectroscopic Imager mission. STIX has a higher sensitivity than RHESSI, with comparable image quality and spectral and spatial resolution. It will be able to observe thermal and non-thermal emission from nanoflares up to the largest X- class events. STIX consists of three main parts: 1. An X-ray window, 2. An imager with 32 subcollimators, and 3. A spectrometer with 32 Cadmium Telluride (CdTe) X-ray detectors The transmission through the grid pairs to the detectors is a very sensitive function of the direction of incidence of the X-ray flux. The relative count rates of the detectors behind the different sets of grids encode the spatial information that can be subsequently decoded on the ground to reconstruct images of the source region at different X-ray energies.