KPL/IK STIX Instrument Kernel =========================================================================== This instrument kernel (I-kernel) briefly describes and contains orientative information of the Field-of-View (FoV) and/or Field-of-Regard (FoR) of and the line of sight (boresight) of the X-ray Spectrometer/Telescope (STIX) sensors. DISCLAIMER: This I-kernel should not be used as a reference for the instrument nor for data analysis for the FoVs will not be updated to reflect best known / calibrated FoVs, nor variation according to mode. Version and Date ----------------------------------------------------------------------------- Version 0.3 -- July 9, 2025 -- Ricardo Valles Blanco ESAC/ESA Updated contact information. Version 0.2 -- March 28, 2018 -- Marc Costa Sitja, ESAC/ESA Incorporated feedback from SOC. Moved FOV frame definition from SOLO_STIX_*_OPT frame to SOLO_STIX_*_ILS frame. Version 0.1 -- October 5, 2017 -- Marc Costa Sitja, ESAC/ESA Reviewed by SOLO SOC (Christopher Watson). Corrected FoV definition. Version 0.0 -- May 16, 2017 -- Marc Costa Sitja, ESAC/ESA Preliminary Version. References ----------------------------------------------------------------------------- 1. ``Kernel Pool Required Reading''. 2. ``Frames Required Reading''. 3. ``C-Kernel Required Reading''. 4. Solar Orbiter Spacecraft Frames Definition Kernel. 5. ``Experiment Interface Document - Part B Solar Orbiter STIX (Spectrometer/Telescope for Imaging X-Rays)'', SO-STIX-EID-30001, P. Orleanski, H. Wiehl, Issue 5, Revision 11, 16th December 2017. Contact Information ----------------------------------------------------------------------------- If you have any questions regarding this file contact the ESA SPICE Service (ESS) at ESAC: Alfredo Escalante Lopez (+34) 91-8131-429 spice@cosmos.esa.int or the Solar Orbiter Science Operations Center at ESAC: sol_soc@esa.int Implementation Notes ----------------------------------------------------------------------------- This file is used by the SPICE system as follows: programs that make use of this frame kernel must "load" the kernel normally during program initialization. Loading the kernel associates the data items with their names in a data structure called the "kernel pool". The SPICELIB routine FURNSH loads a kernel into the pool as shown below: FORTRAN: (SPICELIB) CALL FURNSH ( frame_kernel_name ) C: (CSPICE) furnsh_c ( frame_kernel_name ); IDL: (ICY) cspice_furnsh, frame_kernel_name MATLAB: (MICE) cspice_furnsh ( 'frame_kernel_name' ) PYTHON: (SPICEYPY)* furnsh( frame_kernel_name ) In order for a program or routine to extract data from the pool, the SPICELIB routines GDPOOL, GIPOOL, and GCPOOL are used. See [2] for more details. This file was created and may be updated with a text editor or word processor. * SPICEPY is a non-official, community developed Python wrapper for the NAIF SPICE toolkit. Its development is managed on Github. It is available at: https://github.com/AndrewAnnex/SpiceyPy Naming Conventions ----------------------------------------------------------------------------- Data items are specified using ''keyword=value'' assignments [1]. All keywords referencing values in this I-kernel start with the characters `INS' followed by the NAIF SOLO instrument ID code, constructed using the spacecraft ID number (-144) followed by the NAIF three digit ID number for one of the STIX data item. These IDs are as follows Instrument name ID -------------------- ------- SOLO_STIX -144850 The remainder of the name is an underscore character followed by the unique name of the data item. For example, the STIX boresight direction in the SOLO_STIX_OPT frame (see [2]) is specified by: INS-144850_BORESIGHT The upper bound on the length of the name of any data item identifier is 32 characters. If the same item is included in more than one file, or if the same item appears more than once within a single file, the latest value supersedes any earlier values. Overview ----------------------------------------------------------------------------- From [5]: The Spectrometer Telescope for Imaging X rays (STIX) provides imaging spectroscopy of solar thermal and non-thermal X-ray emissions from ~4 to 150 keV, with unprecedented sensitivity and spatial resolution (near perihelion), and good spectral resolution. STIX plays an important role in enabling Solar Orbiter to achieve two of its major science goals: (1) determining the magnetic connection of Solar Orbiter back to the Sun and (2) understanding the acceleration of electrons at the Sun and their transport into interplanetary space. The remote-sensing X-ray measurements made with STIX will determine the intensity, spectrum, timing, and location of accelerated electrons near the Sun. Flare-accelerated electrons escaping the Sun can then be tracked into the inner heliosphere through their type-III radio emission, observed by RPW (the Radio and Plasma Waves instrument), and detected in situ by STEIN (the SupraThermal Electron sensor) of the Energetic Particle Detector (EPD) suite, to provide direct tracing of the magnetic structure, field line length, and connectivity. In this way, STIX, together with RPW and STEIN, is able to magnetically link the heliospheric region observed in situ back to regions at the Sun where the electrons are accelerated. STIX is based on a Fourier-transform imaging technique. STIX consists of three main parts: 1. A pair of X-ray windows, 2. An imager with 32 subcollimators, and 3. A spectrometer with 32 Cadmium Telluride (CdTe) X-ray detectors, one behind each subcollimator. The X-ray windows are mounted on the spacecraft thermal shield. The imager module is located in front of spectrometer module. Both are internally mounted, Sun-pointed, behind the spacecraft thermal shield. 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 Measurement principle: ~~~~~~~~~~~~~~~~~~~~~~ Observationally, STIX determines the location, spectrum and timing of transient X-ray emission on the Sun at energy ranges that encompass emission from both hot thermal plasmas and bremsstrahlung from energetic electrons. The properties of the electrons that generated the X-rays can be inferred from their X-ray spectrum. The distinction between a thermal plasma and non-thermal electron population is based on the shape of the X-ray spectrum with the latter having a characteristic power law (or broken power law) profile and the former providing a black body spectrum (corresponding to 106 to 108 K). The spectra are very steep and so good spectral resolution is required for their interpretation. There is also an Iron line complex at 6.7 keV which, if isolated, can be interpreted in terms of the thermal electron population. Since a typical flare typically generates both thermal and non-thermal emission, which often are not co-located (for example at the top and footpoints of magnetic loops respectively), both good spatial and spectral resolution are required. The observational objectives are achieved by imaging the Sun as a function of time and energy with enough spatial, spectral and temporal resolution to match the sources of interest. Comparing the resulting images at different energies yields the X-ray spectra of individual features (e.g. footpoints or flaring loops). Comparing the images as a function of time discloses the temporal behavior of the hot plasma and accelerated electrons. The data can also be combined to yield spatially-integrated light curves and spectra. In all cases, the basic observational datum is a single, photometrically-accurate image corresponding to a well-defined time and energy interval. Focusing optics are not a feasible option for arcsecond-class hard X-ray imaging within Solar Orbiter constraints. As a result, STIX uses an indirect Fourier imaging technique based on X-ray collimation. Conceptually, the instrument is made up of three mechanically separate modules: X-ray transparent windows; a passive imager containing front and rear grids; and a Detector/Electronics Module (DEM) containing passivelycooled X-ray detectors and electronics. The imager is comprised of 32 subcollimators, each of which consists of a pair of wellseparated X-ray opaque grids located in front of a corresponding CdTe X-ray detector in the DEM. The X-ray transmission of each grid pair forms a large-scale Moiré pattern on the detector with the properties of these Moiré patterns being very sensitive to the angular distribution of the incident of the X-ray flux. Individual CdTe detector pixels associated with each subcollimator provide ~2 mm spatial resolution which is sufficient to characterize the Moiré pattern formed by its grids. As a result, high-angular resolution X-ray imaging information is encoded into a set of large scale spatial distributions of counts in the detectors. This can be subsequently decoded on the ground to reconstruct an image of the X-ray source.For each detected X-ray, the detectors provide an output pulse proportional to its energy. By reconstructing images using counts within specific energy intervals, the combined system functions as a high resolution X-ray imaging spectrometer. Mounting Alignment ----------------------------------------------------------------------------- Refer to the latest version of the Solar Orbiter Frames Definition Kernel (FK) [4] for the STIX reference frame definitions and mounting alignment information. STIX Apparent Field-of-View Layout ----------------------------------------------------------------------------- For STIX, the front element of the telescope is an X-ray mirror with a a FOV of ~2 degree. This section provides a diagram illustrating the STIX apparent FOV layout in the corresponding reference frames. ^ +Ystix | | --- +---------|---------+ ^ | | | | | | | | | | | | | | | | 2 deg | x-------------> +Zstix | | +Xstix | | | | | | | V | | --- +-------------------+ | 2 deg | Boresight (+X axis) |<----------------->| is into the page | | FOV Definition --------------------------------------------------------------------------- This section contains definitions for the STIX apparent FOVs. These definitions are provided in the format required by the SPICE TOOLKIT function GETFOV. Please note that the FOV reference and cross angles are defined with half angle values. The FOV definitions correspond to the NAIF Body Name: SOLO_STIX. \begindata INS-144850_NAME = 'SOLO_STIX' INS-144850_BORESIGHT = ( -1.000 0.000 0.000 ) INS-144850_FOV_FRAME = 'SOLO_STIX_ILS' INS-144850_FOV_SHAPE = 'RECTANGLE' INS-144850_FOV_CLASS_SPEC = 'ANGLES' INS-144850_FOV_REF_VECTOR = ( 0.000 0.000 1.000 ) INS-144850_FOV_REF_ANGLE = ( 1.000000 ) INS-144850_FOV_CROSS_ANGLE = ( 1.000000 ) INS-144850_FOV_ANGLE_UNITS = 'DEGREES' \begintext Platform ID ----------------------------------------------------------------------------- This number is the NAIF instrument ID of the platform on which the channels are mounted. For all channels this platform is the spacecraft. \begindata INS-144900_PLATFORM_ID = ( -144000 ) \begintext End of IK file.