KPL/IK Star Tracker Instrument kernel ============================================================================= This instrument kernel (I-kernel) contains the JUVENTAS Star Trackers (STR) optics, detector, and field-of-view parameters. Version and Date ----------------------------------------------------------------------------- Version 0.0 -- August 25, 2023 -- Rafael Andres Blasco, ESA/ESAC Initial release. References ----------------------------------------------------------------------------- 1. HERA Frames Definition Kernel (FK), latest version. 2. ''Kernel Pool Required Reading'', NAIF. 3. Hera Frames Definition Kernel (FK), latest version. 4. Juventas Spacecraft Frames Kernel (FK), latest version. 5. ``Juventas Cubesat Instruments'', https://www.heramission.space/hera-mission-juventas-cubesat 6. ``Juventas'', https://www.nanosats.eu/sat/juventas 7. Email exchange with Tjorven Delabie from ArcsecSpace, the manufacturer of Twinkle Star Tracker 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 ------------------------------------------------------------------------------ Applications that need SPICE I-kernel data must ``load'' the I-kernel file, normally during program initialization. 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''. The application program may then obtain the value(s) for any IK data item using the SPICELIB routines GDPOOL, GIPOOL, GCPOOL. Routine GETFOV may be used if the file contains instrument field-of-view (FOV) specification. See [1] for details. This file was created with, and can be updated with a text editor or word processor. 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 JUVENTAS instrument ID code, constructed using the spacecraft ID number (-15513) followed by the NAIF three digit ID number. The ID numbers are defined in [4] as follows: Instrument name ID -------------------- --------- JUVENTAS_STR-1 -15513510 JUVENTAS_STR-2 -15513520 The remainder of the keyword is an underscore character followed by the unique name of the data item. For example, the boresight of STR is specified by INS-15513510_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 [5] and [7]: From a functional point of view, the Twinkle 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 Detector is a CCD 1024 x 1024 pixels and has a FOV of 10.6 degrees. The size of each pixel is 2.9um x 2.9um. | 10.6 deg | Boresight (+X axis) |<----------------->| is out the page | | 1024 pixels/line --- +-------------------+ ^ | ^ +Zst | | | | | | | +Xstr | |10.6 deg 1024 | o -------------> +Ystr | lines | | | | | v | | --- (0,0)----------------+ Pixel 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: JUVENTAS_STR-1 and JUVENTAS_STR-2. The set of assignments in the data section below defines the STR FOVs with respect to the corresponding frames to be a rectangle with the corners defined by the first and last pixels of the first and last lines of the CCD and the boresight along the +X axis. STR: \begindata INS-15513510_FOV_FRAME = 'JUVENTAS_STR-1' INS-15513510_FOV_SHAPE = 'RECTANGLE' INS-15513510_BORESIGHT = ( 1.0, 0.0, 0.0 ) INS-15513510_FOV_CLASS_SPEC = 'ANGLES' INS-15513510_FOV_REF_VECTOR = ( 0.0, 0.0, 1.0 ) INS-15513510_FOV_REF_ANGLE = ( 5.3 ) INS-15513510_FOV_CROSS_ANGLE = ( 5.3 ) INS-15513510_FOV_ANGLE_UNITS = 'DEGREES' INS-15513520_FOV_FRAME = 'JUVENTAS_STR-2' INS-15513520_FOV_SHAPE = 'RECTANGLE' INS-15513520_BORESIGHT = ( 1.0, 0.0, 0.0 ) INS-15513520_FOV_CLASS_SPEC = 'ANGLES' INS-15513520_FOV_REF_VECTOR = ( 0.0, 0.0, 1.0 ) INS-15513520_FOV_REF_ANGLE = ( 5.3 ) INS-15513520_FOV_CROSS_ANGLE = ( 5.3 ) INS-15513520_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 16 Focal Number, 2 Field of view, deg 10.6 True/Effective field of view, deg TBD Pixel Size (iFoV), arcsec 37.26 ----------------------------------------------------------------- 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-15513510_FOCAL_LENGTH = ( 16.0 ) INS-15513510_F/RATIO = ( 2.0 ) INS-15513510_FOV_ANGULAR_SIZE = ( 0.09250245035569947 ) INS-15513510_IFOV = ( 0.0003466417819933 ) INS-15513520_FOCAL_LENGTH = ( 16.0 ) INS-15513520_F/RATIO = ( 2.0 ) INS-15513520_FOV_ANGULAR_SIZE = ( 0.09250245035569947 ) INS-15513520_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, mm 2.9e-3 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-15513510_PIXEL_SIZE = ( 37.26 ) INS-15513510_PIXEL_SAMPLES = ( 1024 ) INS-15513510_PIXEL_LINES = ( 1024 ) INS-15513510_CCD_CENTER = ( 511, 511 ) INS-15513520_PIXEL_SIZE = ( 37.26 ) INS-15513520_PIXEL_SAMPLES = ( 1024 ) INS-15513520_PIXEL_LINES = ( 1024 ) INS-15513520_CCD_CENTER = ( 511, 511 ) \begintext Platform ID ------------------------------------------------------------------------------- This number is the NAIF instrument ID of the platform on which the sensors are mounted. For the Juventas Star Trackers (STRs) platform is spacecraft. Please refer to the latest version of the Juventas NAIF ID Codes Definitions [4] for mapping of ID codes to sensor and structure names. \begindata INS-15513510_PLATFORM_ID = ( -15513 ) INS-15513520_PLATFORM_ID = ( -15513 ) \begintext End of IK file.