KPL/IK NAVCAM Instrument kernel =========================================================================== This instrument kernel (I-kernel) contains JUICE Navigation Camera (NAVCAM) optics, detector, and field-of-view parameters. Version and Date --------------------------------------------------------------------------- Version 0.1 -- April 7, 2021 -- Alfredo Escalante Lopez, ESAC/ESA Added Optical and Detector parameters sections and information. Version 0.0 -- October 24, 2016 -- Marc Costa Sitja, ESAC/ESA Initial Release based on the Rosetta Navigation Camera (NAVCAM) instrument kernel. References --------------------------------------------------------------------------- 1. ``Kernel Pool Required Reading'' 2. ``C-kernel Required Reading'' 3. JUICE Frames Definition Kernel (FK), latest version. 4. ``JUICE Spacecraft Design Report'', JUI-ADST-SYS-DD-000122, Issue 3, Airbus Defense and Space, 25 November 2018 Contact Information ------------------------------------------------------------------------ If you have any questions regarding this file contact SPICE support at ESAC: Alfredo Escalante Lopez (+34) 91-8131-429 spice@sciops.esa.int or NAIF at JPL: Boris Semenov (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. 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 [3]. All keywords referencing values in this I-kernel start with the characters `INS' followed by the NAIF JUICE instrument ID code. The Navigation Camera instrument IDs are defined in [3] as follows: Instrument name ID -------------------- ------- JUICE_NAVCAM-1 -28051 JUICE_NAVCAM-2 -28052 The remainder of the keyword is an underscore character followed by the unique name of the data item. For example, the boresight of the JUICE NavCam 1 (NAVCAM-1) is specified by INS-28051_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 --------------------------------------------------------------------------- NavCam (Navigation Cameras) is a key instrument for the spacecraft navigation. To achieve enough precise navigation in Jovian environment, ground based radiometric measurements are not sufficient, therefore it is paramount to measure the position of the Jupiter moons in-flight, with high accuracy. To achieve this measurement, the NavCam assesses the position of the moon and stars in its field of view in an inertial reference frame. The combination of these two measurements gives the accurate position of each of Jupiter icy moons. The stars processing is similar to that of a star tracker and is performed inside the camera, whereas the moons detection is done on-ground from images captured by the camera. In addition to the above primary mission, the navigation camera will also be used by the spacecraft attitude control loop during close fly-bys in order to improve the spacecraft absolute pointing performance. The NavCam is a standalone unit compose of 3 main elements [4]: - Detection unit, which contains the detector, its cooling system (TEC) and the electronic boards mounted in an aluminum structure. The Detection Unit supports all connectors necessary for NavCam command, power supply and two redundant spacewire. Radiation shielding is done on the Detection Unit through high thickness of the box walls (about 9 mm). A square diaphragm around the detector avoids high reflection between detector electronics and lenses. - Lens assembly, which receives the optical glass components, interface with the Detection Unit, supports the Baffle Assembly and the alignment cube. It is mounted on the mounting plane interface and is covered by MLI except for the feet. The glasses are radiation tolerant (doped glasses). - Baffle, made of aluminum alloy machined in one piece to minimize mass but mounted on the lens assembly with a titanium baffle support to ensure the thermal decoupling. The outside coating is Alodine 1200 but is covered with MLI and the inside coating is black paint for straylight performance. The two JUICE Navigation Cameras (NavCam) are accommodated on the optical bench close to the STR-OH providing high pointing accuracy and stability to all the units. NavCam boresight axes are aligned to the spacecraft nadir-pointed axis (+Z). A potential small angular offset by 1.5 degrees in the –X direction will be investigated later (decision can be deferred late in the project). Indeed it would have an interest for the Closed Loop Attitude Guidance concept implemented in the baseline, to maximise the limb measurements availability prior to the flybys closest approach, thus improving navigation and therefore pointing performance. The spacecraft +X axis is always in the shadow during flybys for thermal constraints, so the camera boresight would be off-pointed towards the moon lit limb during the approach, which may improve the performance. Apparent FOV Layout --------------------------------------------------------------------------- This section provides a diagram illustrating the NAVCAM apparent FOV layout in the corresponding reference frames. ^ +Xcam | (+Xsc) | --- +---------|---------+ ^ | | | | 4 deg | | | | | | | | | | | | 1024 | x-------------> +Ycam | lines | +Zcam | (+Ysc) | | | | | | V | | --- Pixel (0,0)-----------------+ 1024 pixels/line | 4 deg | Boresight (+Z axis) |<----------------->| is into the page | | Nominally the +Xcam and +Ycam axes are co-aligned with the respective spacecraft reference frame axes +Xsc and +Ysc. According to the chosen convention the pixel coordinates start with zero in the lower left corner in the orientation shown in the sketch above. The orientation of the +Xcam and +Ycam axes is such that line and column number counts increase with increasing coordinate value. However, the optics of the instrument introduces an inversion of the image. This means that the signs of both coordinate values need to be reversed when transforming the position of an object in space into image coordinates. Or in other words, the image needs to be rotated by 180 degrees in order to match the orientation of the imaged scene. Mounting Alignment --------------------------------------------------------------------------- Refer to the latest version of the JUICE Frames Definition Kernel (FK) [3] for the NAVCAM reference frame definitions and mounting alignment information. Optical Parameters --------------------------------------------------------------------------- The following NAVCAM optical parameters are included in the data section below, from [4]: -------------------------------------------- parameter value -------------------------------------------- Focal Length, mm 262.5 f/ratio 5.25 Field of view (deg) along Xcam 4 along Ycam 4 Pixel Angular Size (arcsec) 14.0625 -------------------------------------------- The keywords below provide nominal data for both cameras. Angular size values in the keywords are given in radians, with the Xcam size being the first value and the Ycam size being the second value in each pair. \begindata INS-28051_FOCAL_LENGTH = ( 262.5 ) INS-28051_F/RATIO = ( 5.25 ) INS-28051_FOV_ANGULAR_SIZE = ( 0.069837, 0.069837 ) INS-28051_IFOV = ( 0.0000682 ) INS-28052_FOCAL_LENGTH = ( 262.5 ) INS-28052_F/RATIO = ( 5.25 ) INS-28052_FOV_ANGULAR_SIZE = ( 0.069837, 0.069837 ) INS-28052_IFOV = ( 0.0000682 ) \begintext CCD Parameters --------------------------------------------------------------------------- The NAVCAM 1 and 2 use the HAS 2 detector of the same type with the following nominal geometry parameters, from [4]: ----------------------------------------------------------------- parameter value note ----------------------------------------------------------------- Pixel Size, microns along Xcam 18 along Ycam 18 Detector Array Size, pixels along Xcam 1024 along Ycam 1024 ----------------------------------------------------------------- The values are given in microns for PIXEL_SIZE keywords and in counts for PIXEL_SAMPLES, PIXEL_LINES, and CENTER keywords. \begindata INS-28051_PIXEL_SIZE = ( 18, 18 ) INS-28051_PIXEL_SAMPLES = ( 1024 ) INS-28051_PIXEL_LINES = ( 1024 ) INS-28051_CCD_CENTER = ( 511.5, 511.5 ) INS-28052_PIXEL_SIZE = ( 18, 18 ) INS-28052_PIXEL_SAMPLES = ( 1024 ) INS-28052_PIXEL_LINES = ( 1024 ) INS-28052_CCD_CENTER = ( 511.5, 511.5 ) \begintext FOV Definitions --------------------------------------------------------------------------- This section contains definitions for the NAVCAM 1 and 2 FOVs. These definitions are provided in the format required by the SPICE (CSPICE) function GETFOV (getfov_c). The set of assignments in the data section below defines the NAVCAM-1/2 FOV with respect to the JUICE_NAVCAM-1/2 frame 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 +Z axis of the JUICE_NAVCAM-1/2 frame. This FOV definition uses angular extent style specification with the angular sizes along the Xcam and Ycam axes taken from the 'Optical Parameters' section above. \begindata INS-28051_FOV_FRAME = 'JUICE_NAVCAM-1' INS-28051_FOV_SHAPE = 'RECTANGLE' INS-28051_BORESIGHT = (0.0 0.0 1.0) INS-28051_FOV_CLASS_SPEC = 'ANGLES' INS-28051_FOV_REF_VECTOR = (1.0 0.0 0.0) INS-28051_FOV_REF_ANGLE = ( 2.000 ) INS-28051_FOV_CROSS_ANGLE = ( 2.000 ) INS-28051_FOV_ANGLE_UNITS = 'DEGREES' INS-28052_FOV_FRAME = 'JUICE_NAVCAM-2' INS-28052_FOV_SHAPE = 'RECTANGLE' INS-28052_BORESIGHT = (0.0 0.0 1.0) INS-28052_FOV_CLASS_SPEC = 'ANGLES' INS-28052_FOV_REF_VECTOR = (1.0 0.0 0.0) INS-28052_FOV_REF_ANGLE = ( 2.000 ) INS-28052_FOV_CROSS_ANGLE = ( 2.000 ) INS-28052_FOV_ANGLE_UNITS = 'DEGREES' \begintext Optical Distortion --------------------------------------------------------------------------- [TBD]. Platform ID --------------------------------------------------------------------------- This number is the NAIF instrument ID of the platform on which the cameras are mounted. For both cameras this platform is the spacecraft. \begindata INS-28051_PLATFORM_ID = ( -28000 ) INS-28052_PLATFORM_ID = ( -28000 ) \begintext End of IK file.