KPL/IK HERA Star Tracker Instrument kernel ============================================================================= This instrument kernel (I-kernel) contains HERA Star Trackers (STR) optics, detector, and field-of-view parameters. Version and Date ----------------------------------------------------------------------------- Version 0.0 -- July 4, 2023 -- Rafael Andres Blasco, ESA/ESAC Initial release. References ----------------------------------------------------------------------------- 1. HERA Frames Definition Kernel (FK), latest version. 2. ''Kernel Pool Required Reading'', NAIF. Contact Information ----------------------------------------------------------------------------- If you have any questions regarding this file contact the ESA SPICE Service at ESAC: Alfredo Escalante Lopez (+34) 91-8131-429 spice@sciops.esa.int or NAIF at JPL: Boris Semenov +1 (818) 354-8136 Boris.Semenov@jpl.nasa.gov 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. * SPICEYPY 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 HERA instrument ID code. The Star Tracker instrument IDs are defined in [1] as follows: Instrument name ID -------------------- ------- HERA_STR-1 -999061 HERA_STR-2 -999062 The remainder of the keyword is an underscore character followed by the unique name of the data item. For example, the boresight of the Star Tracker 1 (STR-1) is specified by INS-999061_BORESIGHT The upper bound on the length of all keywords is 32 characters. If a keyword is included in more than one file, or if the same keyword appears more than once within a single file, the last assignment supersedes any earlier assignments. Description ----------------------------------------------------------------------------- From a functional point of view, the Autonomous Star Trackers can be seen as a video camera plus an image processing unit that, starting from an image of the sky, extracts the attitude information for the AOCS, measured with respect to the J2000 inertial reference system. The STR can track up to 15 stars simultaneously and consists of a Single box that contains the optical head, the main electronics and a baffle which is thermally decoupled from the box. From [1]: The Detector consists is a HAS APS (1024 x 1024 pixels manufactured by Cypress) and has a circular FOV of 20 degrees with an Effective Focal Length of 51.9 mm. Mounting Alignment ----------------------------------------------------------------------------- Refer to the latest version of the HERA Frames Definition Kernel (FK) [1] for the Star Trackers reference frames definitions and mounting alignment information. FOV Definitions ----------------------------------------------------------------------------- This section contains definitions for the Star Tracker FOVs. These definitions are provided in the format required by the SPICE (CSPICE) function GETFOV (getfov_c). Please note that the FOV reference and cross angles are defined with half angle values. The FoV definition corresponds to the NAIF Body Names: HERA_STR-OH1 and HERA_STR-OH2. \begindata INS-999061_NAME = 'HERA_STR-1' INS-999061_BORESIGHT = ( 0.000, 0.000, 1.000 ) INS-999061_FOV_FRAME = 'HERA_STR-OH1' INS-999061_FOV_SHAPE = 'CIRCLE' INS-999061_FOV_CLASS_SPEC = 'ANGLES' INS-999061_FOV_REF_VECTOR = ( 0.000, 1.000, 0.000 ) INS-999061_FOV_REF_ANGLE = ( 20.0 ) INS-999061_FOV_ANGLE_UNITS = 'DEGREES' INS-999062_NAME = 'HERA_STR-2' INS-999062_BORESIGHT = ( 0.000, 0.000, 1.000 ) INS-999062_FOV_FRAME = 'HERA_STR-OH2' INS-999062_FOV_SHAPE = 'CIRCLE' INS-999062_FOV_CLASS_SPEC = 'ANGLES' INS-999062_FOV_REF_VECTOR = ( 0.000, 1.000, 0.000 ) INS-999062_FOV_REF_ANGLE = ( 20.0 ) INS-999062_FOV_ANGLE_UNITS = 'DEGREES' \begintext Optical Parameters ----------------------------------------------------------------------------- The following STR optical parameters are included in the data section below, from [3]: ----------------------------------------------------------------- Parameter ----------------------------------------------------------------- Waveband, nm 500-900 Effective Focal Length, mm 51.9 Focal Number, 1.48 Field of view, deg 20.0 True/Effective field of view, deg 16.0 Pixel Size (iFoV), arcsec 71.5 Distortion, 0.72% at 10 deg Spot Size, 2-4 pixels ----------------------------------------------------------------- The keywords below provide nominal data for both cameras. Angular size values in the keywords are given in radians. Angular size is half-cone angle. \begindata INS-999061_FOCAL_LENGTH = ( 51.9 ) INS-999061_F/RATIO = ( 1.48 ) INS-999061_FOV_ANGULAR_SIZE = ( 0.2792526803190927 ) INS-999061_IFOV = ( 0.0003466417819933 ) INS-999062_FOCAL_LENGTH = ( 51.9 ) INS-999062_F/RATIO = ( 1.48 ) INS-999062_FOV_ANGULAR_SIZE = ( 0.2792526803190927 ) INS-999062_IFOV = ( 0.0003466417819933 ) \begintext CCD Parameters ----------------------------------------------------------------------------- The STR 1 and 2 use the CCD detector of the same type with the following nominal geometry parameters, from [3]: ----------------------------------------------------------------- parameter value note ----------------------------------------------------------------- Pixel Size, arsec 71.5 Detector Array Size along Xstr 1024 along Ystr 1024 ----------------------------------------------------------------- The values are given in counts for PIXEL_SIZE, PIXEL_SAMPLES, PIXEL_LINES and CENTER keywords. \begindata INS-999061_PIXEL_SIZE = ( 71.5 ) INS-999061_PIXEL_SAMPLES = ( 1024 ) INS-999061_PIXEL_LINES = ( 1024 ) INS-999061_CCD_CENTER = ( 511, 511 ) INS-999062_PIXEL_SIZE = ( 71.5 ) INS-999062_PIXEL_SAMPLES = ( 1024 ) INS-999062_PIXEL_LINES = ( 1024 ) INS-999062_CCD_CENTER = ( 511, 511 ) \begintext End of IK file.