KPL/IK HERA Asteroid Spectral Imager Instrument kernel ============================================================================== This instrument kernel (I-kernel) contains the Asteroid Spectral Imager (ASPECT) optics, detector, and field-of-view parameters. Version and Date ------------------------------------------------------------------------------ Version 0.0 -- June 24, 2022 -- Ricardo Valles Blanco, ESAC/ESA Initial release. References ------------------------------------------------------------------------------ 1. ``Kernel Pool Required Reading'' 2. ``C-kernel Required Reading'' 3. Hera Frames Definition Kernel (FK), latest version. 4. Milani Spacecraft Frames Kernel (FK), latest version. 5. ``Milani Cubesat Instruments'', https://www.heramission.space/hera-mission-milani-cubesat 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 HERA instrument ID code, constructed using the spacecraft ID number (-99902) followed by the NAIF three digit ID number. The ID numbers are defined in [4] as follows: Instrument name ID -------------------- --------- MILANI_ASPECT_VIS -99902110 MILANI_ASPECT_NIR1 -99902120 MILANI_ASPECT_NIR2 -99902130 MILANI_ASPECT_SWIR -99902140 The remainder of the keyword is an underscore character followed by the unique name of the data item. For example, the f/ratio of the ASPECT_NIR1 is specified by INS-99902120_F/RATIO 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]: ASPECT is a miniaturised hyperspectral imager extending from the visible up to shortwave infrared (SWIR) wavelengths. In contrast to more traditional spatial scanning imaging spectrometres, the Asteroid Spectral Imager takes 2D snapshots at a given wavelength. When multiple snapshots are combined, a spectral datacube is formed, where the wavelength bands are separated in the time domain. The instrument is split into four measurement channels, one in the visible (VIS), and two in the NIR and one in SWIR. The VIS and NIR channels are imaging spectrometres, while the SWIR channel only measures a single point. The spectral separation is done by a tunable Fabry-Perot Interferometre (FPI). All four channels have dedicated FPIs optimised for the desired wavelength range. The imaged wavelengths are freely selectable within these ranges, and the targeted spectral resolution is ca. 10 - 50 nm. All four channels can be operated simultaneously and are independent of each other: even if a single image sensor or FPI is lost, the mission can still carry on with limited capabilities. Mounting Alignment ------------------------------------------------------------------------------ Refer to the latest version of the Milani Spacecraft Frames Kernel (FK) [4] for the ASPECT reference frame definitions and mounting alignment information. Apparent FOV Layout ------------------------------------------------------------------------------ This section provides a diagram illustrating the ASPECT_VIS, ASPECT_NIR1, ASPECT_NIR2 and ASPECT_SWIR apparent FOV layouts in the corresponding reference frames. For ASPECT_VIS the pixel (0,0) is in the lower left corner of the image, and pixel (1023,1023) is in the top right corner. +X, +Y, +Z axes are defined in the Milani Spacecraft Frames Kernel (FK) [4]. | 10 deg | Boresight (+Z axis) |<----------------->| is into the page | | 1024 pixels/line --- +-------------------+ ^ | | | | | | | +Zvis | | 10 deg 1024 | x-------------> +Xvis | lines | | | | | | | V | | | --- (0,0)-------|---------+ Pixel | | v +Yvis For ASPECT_NIR1 and ASPECT_NIR2 the pixel (0,0) is in the lower left corner of the image, and pixel (639,511) is in the top right corner. +X, +Y, +Z axes are defined in the Milani Spacecraft Frames Kernel (FK) [4]. | 6.7 deg | Boresight (+Z axis) |<----------------->| is into the page | | 640 pixels/line --- +-------------------+ ^ | | | | +Znir1 | | | +Znir2 | |5.4 deg 512 | x-------------> +Xnir1 | lines | | | +Xnir2 | | | | v | | | --- (0,0)-------|---------+ Pixel | | +Ynir1 v +Ynir2 The ASPECT_SWIR FOV has a circular shape with an aperture of 5 degrees and 1 pixel resolution. +X, +Y, +Z axes are defined in the Milani Spacecraft Frames Kernel (FK) [4]. | 5 deg | Boresight (+Z axis) |<----------->| is into the page | | --- . --- . ^ / \ | . . | 5 deg | x---------> +Xswir | . | . v \ | / --- . _|_ . | v +Yswir Optical Parameters ------------------------------------------------------------------------------ The following ASPECT nominal first order optical parameters are, from [5]: -------------------------------------------------------------------------- parameter VIS NIR1 NIR2 SWIR -------------------------------------------------------------------------- Focal Length, mm ? ? ? ? f/ratio ? ? ? ? IFOV, rad/pixel 0.00017 182e-6x184e-6 182e-6x184e-6 0.0872665 Field of view, deg 10 x 10 6.7 x 5.4 6.7 x 5.4 5.0 Spectral range, mm 500 - 900 850 - 1275 1225 - 1650 1600 - 2500 No. spectral bands Ca. 14 Ca. 14 Ca. 14 Ca. 30 Spectral res., nm < 20 < 40 < 40 < 40 -------------------------------------------------------------------------- ASPECT_VIS: \begindata INS-99902110_IFOV = ( 0.000170442, 0.000170442 ) INS-99902110_FOV_ANGULAR_SIZE = ( 0.174533, 0.174533 ) \begintext ASPECT_NIR1 and ASPECT_NIR2: \begindata INS-99902120_IFOV = ( 0.000182714, 0.000184077 ) INS-99902120_FOV_ANGULAR_SIZE = ( 0.116937, 0.0942478 ) INS-99902130_IFOV = ( 0.000182714, 0.000184077 ) INS-99902130_FOV_ANGULAR_SIZE = ( 0.116937, 0.0942478 ) \begintext ASPECT_SWIR: \begindata INS-99902140_IFOV = ( 0.0872665 ) INS-99902140_FOV_ANGULAR_SIZE = ( 0.0872665 ) \begintext CCD Parameters ------------------------------------------------------------------------------ The following ASPECT nominal geometry parameters are, from [5]. --------------------------------------------------------------------------- parameter VIS NIR1 NIR2 SWIR --------------------------------------------------------------------------- Pixel size, um 5.5 x 5.5 15 x 15 15 x 15 1000 Detector Array Size 1024 x 1024 640 x 512 640 x 512 1 Detector Array Center 511.5 x 511.5 319.5 x 255.5 319.5 x 255.5 0.5 --------------------------------------------------------------------------- The values are given in microns for PIXEL_SIZE keywords and in counts for PIXEL_SAMPLES, PIXEL_LINES, and CENTER keywords. ASPECT_VIS: \begindata INS-99902110_PIXEL_SIZE = ( 5.5, 5.5 ) INS-99902110_PIXEL_SAMPLES = ( 1024 ) INS-99902110_PIXEL_LINES = ( 1024 ) INS-99902110_CCD_CENTER = ( 511.5, 511.5 ) \begintext ASPECT_NIR1 and ASPECT_NIR2: \begindata INS-99902120_PIXEL_SIZE = ( 15.0, 15.0 ) INS-99902120_PIXEL_SAMPLES = ( 640 ) INS-99902120_PIXEL_LINES = ( 512 ) INS-99902120_CCD_CENTER = ( 319.5, 255.5 ) INS-99902130_PIXEL_SIZE = ( 15.0, 15.0 ) INS-99902130_PIXEL_SAMPLES = ( 640 ) INS-99902130_PIXEL_LINES = ( 512 ) INS-99902130_CCD_CENTER = ( 319.5, 255.5 ) \begintext ASPECT_SWIR: \begindata INS-99902140_PIXEL_SIZE = ( 1000.0 ) INS-99902140_PIXEL_SAMPLES = ( 1 ) INS-99902140_PIXEL_LINES = ( 1 ) INS-99902140_CCD_CENTER = ( 0.5, 0.5 ) \begintext Filter Parameters ------------------------------------------------------------------------------ TBD. FOV Definitions ------------------------------------------------------------------------------ This section contains definitions for the ASPECT FOVs. These definitions are provided in a format required by the SPICE (CSPICE) function GETFOV (getfov_c). The set of assignments in the data section below defines the ASPECT 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 +Z axis. This FOV definition uses the FOV_ANGULAR_SIZE values from the ``Optical Parameters'' section above converted to degrees. ASPECT_VIS: \begindata INS-99902110_FOV_FRAME = 'MILANI_ASPECT_VIS' INS-99902110_FOV_SHAPE = 'RECTANGLE' INS-99902110_BORESIGHT = ( 0.0, 0.0, 1.0 ) INS-99902110_FOV_CLASS_SPEC = 'ANGLES' INS-99902110_FOV_REF_VECTOR = ( 1.0, 0.0, 0.0 ) INS-99902110_FOV_REF_ANGLE = ( 5.0 ) INS-99902110_FOV_CROSS_ANGLE = ( 5.0 ) INS-99902110_FOV_ANGLE_UNITS = 'DEGREES' \begintext ASPECT_NIR1: \begindata INS-99902120_FOV_FRAME = 'MILANI_ASPECT_NIR1' INS-99902120_FOV_SHAPE = 'RECTANGLE' INS-99902120_BORESIGHT = ( 0.0, 0.0, 1.0 ) INS-99902120_FOV_CLASS_SPEC = 'ANGLES' INS-99902120_FOV_REF_VECTOR = ( 1.0, 0.0, 0.0 ) INS-99902120_FOV_REF_ANGLE = ( 3.35 ) INS-99902120_FOV_CROSS_ANGLE = ( 2.7 ) INS-99902120_FOV_ANGLE_UNITS = 'DEGREES' \begintext ASPECT_NIR2: \begindata INS-99902130_FOV_FRAME = 'MILANI_ASPECT_NIR2' INS-99902130_FOV_SHAPE = 'RECTANGLE' INS-99902130_BORESIGHT = ( 0.0, 0.0, 1.0 ) INS-99902130_FOV_CLASS_SPEC = 'ANGLES' INS-99902130_FOV_REF_VECTOR = ( 1.0, 0.0, 0.0 ) INS-99902130_FOV_REF_ANGLE = ( 3.35 ) INS-99902130_FOV_CROSS_ANGLE = ( 2.7 ) INS-99902130_FOV_ANGLE_UNITS = 'DEGREES' \begintext ASPECT_SWIR: \begindata INS-99902140_FOV_FRAME = 'MILANI_ASPECT_SWIR' INS-99902140_FOV_SHAPE = 'CIRCLE' INS-99902140_BORESIGHT = ( 0.0, 0.0, 1.0 ) INS-99902140_FOV_CLASS_SPEC = 'ANGLES' INS-99902140_FOV_REF_VECTOR = ( 1.0, 0.0, 0.0 ) INS-99902140_FOV_REF_ANGLE = ( 2.5 ) INS-99902140_FOV_ANGLE_UNITS = 'DEGREES' \begintext Optical Distortion ------------------------------------------------------------------------------ TBD. Platform ID ------------------------------------------------------------------------------- This number is the NAIF instrument ID of the platform on which the sensors are mounted. For the Asteroid Spectral Imager (ASPECT) platform is spacecraft. Please refer to the latest version of the Milani NAIF ID Codes Definitions [4] for mapping of ID codes to sensor and structure names. \begindata INS-99902110_PLATFORM_ID = ( -99902 ) INS-99902120_PLATFORM_ID = ( -99902 ) INS-99902130_PLATFORM_ID = ( -99902 ) INS-99902140_PLATFORM_ID = ( -99902 ) \begintext End of IK file.