KPL/IK Star Tracker Instrument kernel =============================================================================== This instrument kernel (I-kernel) contains TGO Star Trackers (STR) optics, detector, and field-of-view parameters. Version and Date ------------------------------------------------------------------------------- Version 0.3 -- June 6, 2019 -- Marc Costa Sitja, ESA/ESAC Updated FOV shape to rectangle. Updated and added Optical and CCD parameters. Version 0.2 -- October 12, 2018 -- Marc Costa Sitja, ESA/ESAC Updated the boresight definition (to unitary) for TGO_STR-1 and TGO_STR-2 in order to avoid an error using GFTFOV with SPICE Toolkit versions earlier than N067. Version 0.1 -- May 15, 2018 -- Marc Costa Sitja, ESA/ESAC Updated STRs IDs. Version 0.0 -- March 27, 2018 -- Marc Costa Sitja, ESA/ESAC Initial release. References ------------------------------------------------------------------------------- 1. TGO Frames Definition Kernel (FK), latest version. 2. ''Kernel Pool Required Reading''. 3. ``ExoMars AA-STR User Manual'', EXM-OM-MAN-SG-0001, Revision E, Selex ES, 16 November 2015. 4. ``ExoMars AA-STR Design Report'', EXM-OM-DRP-SG-0001, Revision E, Selex ES, 17 April 2015. Contact Information ------------------------------------------------------------------------------- If you have any questions regarding this file contact the ESA SPICE Service (ESS) at ESAC: Marc Costa Sitja (+34) 91-8131-457 esa_spice@sciops.esa.int, marc.costa@esa.int or SPICE support at IKI: Alexander Abbakumov +7 (495) 333-40-13 aabbakumov@romance.iki.rssi.ru or NAIF at JPL: Boris Semenov +1 (818) 354-8136 Boris.Semenov@jpl.nasa.gov Implementation Notes ------------------------------------------------------------------------------- Applications that need SPICE I-kernel data must ``load'' the I-kernel file, normally during program initialisation. The SPICE routine FURNSH loads a kernel file into the pool as shown below. CALL FURNSH ( 'frame_kernel_name' ) -- FORTRAN furnsh_c ( "frame_kernel_name" ); -- C cspice_furnsh, frame_kernel_name -- IDL cspice_furnsh( 'frame_kernel_name' ) -- MATLAB Loading the kernel using the SPICELIB routine FURNSH causes the data items and their associated values present in the kernel to become associated with a data structure called the ``kernel pool''. Once the file has been loaded, the SPICE routine GETFOV (getfov_c in C, cspice_getfov in IDL and MATLAB) can be used to retrieve FOV parameters for a given instrument or structure. The application program may obtain the value(s) for any other IK data item using the SPICELIB routines GDPOOL, GIPOOL, GCPOOL (gdpool_c, gipool_c, gcpool_c in C, cspice_gdpool, cspice_gipool, cspice_gcpool in IDL and MATLAB). See [1] for details. This file was created with, and can be updated with a text editor or word processor. Naming Conventions and Conventions for Specifying Data ------------------------------------------------------------------------------- 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 TGO instrument ID code. The Star Tracker instrument IDs are defined in [1] as follows: Instrument name ID -------------------- ------- TGO_STR-1 -143041 TGO_STR-2 -143042 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-143041_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. Overview ------------------------------------------------------------------------------- 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. The Detector consists is a HAS APS (1024 x 1024 pixels manufactured by Cypress) and has a circular FOV of 20 degrees with a Focal Length of 51.7 mm. Apparent FOV Layout --------------------------------------------------------------------------- This section provides a diagram illustrating the STR-1 and STR-2 detectors apparent FOVs layout in the corresponding reference frames. The STR surface slit creates a rectangular field of view with half cone angle of 10 degrees. The following diagrams illustrate the above field of view in the instrument frame: Y X ins ins ^ / ^ / | / | / | / | / | / | / X | / o Y | / o ins |/ 20.0 ins |/ 20.0 x--------> o--------> |\ Z |\ Z | \ ins | \ ins | \ | \ | \ | \ | \ | \ | \ | \ Plane X = 0 Plane Y = 0 Please note that the FOV reference and cross angles are defined with half angle values. Mounting Alignment ------------------------------------------------------------------------------- Refer to the latest version of the TGO Frames Definition Kernel (FK) [1] for the Star Trackers reference frames definitions and mounting alignment information. Optical Parameters --------------------------------------------------------------------------- The following STR optical parameters are included in the data section below, from [3],[4]: ----------------------------------------------------------------- Parameter ----------------------------------------------------------------- Focal Length, mm 51.7 Effective Focal Length, mm 51.9 Relative Aperture (F Number) 1.48 Field of view (deg) 20.0 Pixel Size (IFOV), arcsec 71.5 Distortion at 10 degrees, % 0.72 Spot Size, pixels 2-4 ----------------------------------------------------------------- The keywords below provide nominal data for both cameras. Angular size values in the keywords are given in radians. \begindata INS-143041_FOCAL_LENGTH = ( 51.9 ) INS-143041_F/RATIO = ( 1.48 ) INS-143041_FOV_ANGULAR_SIZE = ( 0.3490658503988659 ) INS-143041_IFOV = ( 0.0003466417819999 ) INS-143042_FOCAL_LENGTH = ( 51.9 ) INS-143042_F/RATIO = ( 1.48 ) INS-143042_FOV_ANGULAR_SIZE = ( 0.3490658503988659 ) INS-143042_IFOV = ( 0.0003466417819999 ) \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, microns along Xstr 18 along Ystr 18 Detector Array Size along Xstr 1024 along Ystr 1024 ----------------------------------------------------------------- The values are given in counts for PIXEL_SAMPLES, PIXEL_LINES, and CENTER keywords. \begindata INS-143041_PIXEL_SIZE = ( 18, 18 ) INS-143041_PIXEL_SAMPLES = ( 1024 ) INS-143041_PIXEL_LINES = ( 1024 ) INS-143041_CCD_CENTER = ( 511, 511 ) INS-143041_PIXEL_SIZE = ( 18, 18 ) INS-143042_PIXEL_SAMPLES = ( 1024 ) INS-143042_PIXEL_LINES = ( 1024 ) INS-143042_CCD_CENTER = ( 511, 511 ) \begintext 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 Name: TGO_STR-1 and TGO_STR-2. \begindata INS-143041_NAME = 'TGO_STR-1' INS-143041_BORESIGHT = ( 0.000, 0.000, 1.000 ) INS-143041_FOV_FRAME = 'TGO_STR-1' INS-143041_FOV_SHAPE = 'RECTANGLE' INS-143041_FOV_CLASS_SPEC = 'ANGLES' INS-143041_FOV_REF_VECTOR = ( 0.000, 1.000, 0.000 ) INS-143041_FOV_REF_ANGLE = ( 10.0 ) INS-143041_FOV_CROSS_ANGLE = ( 10.0 ) INS-143041_FOV_ANGLE_UNITS = 'DEGREES' INS-143042_NAME = 'TGO_STR-2' INS-143042_BORESIGHT = ( 0.000, 0.000, 1.000 ) INS-143042_FOV_FRAME = 'TGO_STR-2' INS-143042_FOV_SHAPE = 'RECTANGLE' INS-143042_FOV_CLASS_SPEC = 'ANGLES' INS-143042_FOV_REF_VECTOR = ( 0.000, 1.000, 0.000 ) INS-143042_FOV_REF_ANGLE = ( 10.0 ) INS-143042_FOV_CROSS_ANGLE = ( 10.0 ) INS-143042_FOV_ANGLE_UNITS = 'DEGREES' \begintext End of IK file.