The Spectrometer/Telescope for Imaging X-rays (STIX)

¹ University of Applied Sciences and Arts Northwestern Switzerland, Bahnhofstrasse 6, 5210 Windisch, Switzerland
² Space Sciences Laboratory, University of California, 7 Gauss Way, 94720 Berkeley, USA
e-mail: krucker@berkeley.edu
³ ETH Zürich, Rämistrasse 101, 8092 Zürich, Switzerland
⁴ Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
⁵ Space Research Centre, Polish Academy of Sciences, Bartycka 18A, 00-716 Warszawa, Poland
⁶ Astronomical Institute, University of Wroclaw, Wroclaw, Poland
⁷ IRFU, CEA, Université Paris-Saclay, and Université Paris Diderot, AIM, Sorbonne Paris Cité, CEA, CNRS, 91191 Gif-sur-Yvette, France
⁸ IRFU, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
⁹ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France
¹⁰ School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
¹¹ Astronomical Institute, The Czech Academy of Sciences, Ondřejov, Czech Republic
¹² Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
¹³ Institute of Physics, University of Graz, 8010 Graz, Austria
¹⁴ Astrophysics Research Group, School of Physics, Trinity College Dublin, Dublin 2, Ireland
¹⁵ School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin D02 XF86, Ireland
¹⁶ Northumbria University, NE1 8ST Newcastle upon Tyne, UK
¹⁷ Dipartimento di Matematica, Università di Genova, via Dodecaneso 35, 16146 Genova, Italy
¹⁸ NASA Goddard Space Flight Center and Catholic University of America, Greenbelt, MD 20771, USA
¹⁹ Solar Physics Laboratory, Code 671, NASA Goddard Space Flight Center, Greenbelt, MD, USA
²⁰ Van Beek Consultancy, Arnhem, The Netherlands
²¹ Universidad de Alcalá, Space Research Group, 28805 Alcalá de Henares, Spain

Received: 19 December 2019
Accepted: 21 January 2020

Abstract

Aims. The Spectrometer Telescope for Imaging X-rays (STIX) on Solar Orbiter is a hard X-ray imaging spectrometer, which covers the energy range from 4 to 150 keV. STIX observes hard X-ray bremsstrahlung emissions from solar flares and therefore provides diagnostics of the hottest (⪆10 MK) flare plasma while quantifying the location, spectrum, and energy content of flare-accelerated nonthermal electrons.

Methods. To accomplish this, STIX applies an indirect bigrid Fourier imaging technique using a set of tungsten grids (at pitches from 0.038 to 1 mm) in front of 32 coarsely pixelated CdTe detectors to provide information on angular scales from 7 to 180 arcsec with 1 keV energy resolution (at 6 keV). The imaging concept of STIX has intrinsically low telemetry and it is therefore well-suited to the limited resources available to the Solar Orbiter payload. To further reduce the downlinked data volume, STIX data are binned on board into 32 selectable energy bins and dynamically-adjusted time bins with a typical duration of 1 s during flares.

Results. Through hard X-ray diagnostics, STIX provides critical information for understanding the acceleration of electrons at the Sun and their transport into interplanetary space and for determining the magnetic connection of Solar Orbiter back to the Sun. In this way, STIX serves to link Solar Orbiter’s remote and in-situ measurements.