KPL/IK Hayabusa2 TIR Instrument kernel ============================================================================== This instrument kernel (I-kernel) file contains detector, optical, and field-of-view parameters for the Hayabusa2 Thermal Infrared Imager (TIR) instrument. Version and Date ------------------------------------------------------------------------------ Version 0.4b -- September 20, 2024 -- Shin-ya Murakami, ISAS, JAXA - Updated the Optical Parameters and the Detector Parameters sections. Version 0.4a -- July 13, 2022 -- Shin-ya Murakami, ISAS, JAXA - Updated Contact Information. Version 0.3 -- February 20, 2020 -- Yukio Yamamoto, ISAS, JAXA - Updated major version for public release. Version 0.2a -- August 5, 2019 -- Shin-ya Murakami, ISAS, JAXA - Applied cosmetic changes. References ------------------------------------------------------------------------------ 1. Kernel Pool Required Reading 2. GETFOV, getfoc_c, cspice_getfov headers 3. Hayabusa2 FK file, latest version 4. Okada et al., 2017, Thermal Infrared Imaging Experiments of C-Type Asteroid 162173 Ryugu on Hayabusa2, Space Sci. Rev., 208:255-286, https://doi.org/10.1007/s11214-016-0286-8 5. Hayabusa2 Flight Planning Document, PMY-014052, Feb. 2014. Contact Information ------------------------------------------------------------------------------ Takehiko Arai, Ashikaga University, arai.takehiko@ashitech.ac.jp Tatsuaki Okada, ISAS/JAXA, okada@planeta.sci.isas.jaxa.jp Implementation Notes ------------------------------------------------------------------------------ This file is used by the SPICE system as follows: programs that make use of this kernel must ``load'' the kernel, 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 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. This file was created and may be updated with a text editor or word processor. Naming Conventions ------------------------------------------------------------------------------ All names referencing values in this IK file start with the characters `INS' followed by the NAIF Hayabusa2 ID number (-37) followed by a NAIF three digit ID code for one of TIR: HAYABUSA2_TIR-S -37200 The remainder of the keyword name is an underscore character followed by the unique name of the data item. For example, the boresight direction of HAYABUSA2_TIR-S is specified by: INS-37200_BORESIGHT The upper bound on the length of the name of any data item is 32 characters. If the same item is included in more than one file, or if the same item appears more than once within a single file, the latest value supersedes any earlier values. Instrument Description ------------------------------------------------------------------------------ From [4]: The thermal infrared imager TIR onboard Hayabusa2 has been developed to investigate thermo-physical properties of C-type, near-Earth asteroid 162173 Ryugu. TIR is one of the remote science instruments on Hayabusa2 designed to understand the nature of a volatile-rich solar system small body, but it also has significant mission objectives to provide information on surface physical properties and conditions for sampling The thermal infrared imager TIR onboard Hayabusa2 has been developed to investigate thermo-physical properties of C-type, near-Earth asteroid 162173 Ryugu. TIR is one of the remote science instruments on Hayabusa2 designed to understand the nature of a volatile-rich solar system small body, but it also has significant mission objectives to provide information on surface physical properties and conditions for sampling site selection as well as the assessment of safe landing operations. TIR is based on a two-dimensional uncooled micro-bolometer array inherited from the Longwave Infrared Camera LIR on Akatsuki (Fukuhara et al., 2011). TIR takes images of thermal infrared emission in 8 to 12 um with a field of view of 16x12 degrees and a spatial resolution of 0.05 degrees per pixel. TIR covers the temperature range from 150 to 460 K, including the well calibrated range from 230 to 420 K. Temperature accuracy is within 2 K or better for summed images, and the relative accuracy or noise equivalent temperature difference (NETD) at each of pixels is 0.4 K or lower for the well-calibrated temperature range. TIR takes a couple of images with shutter open and closed, the corresponding dark frame, and provides a true thermal image by dark frame subtraction. Data processing involves summation of multiple images, image processing including the StarPixel compression (Hihara et al., 2014), and transfer to the data recorder in the spacecraft digital electronics (DE). Optical Parameters ------------------------------------------------------------------------------ TIR first order optical parameters are included in the data section below, taken from [5]: ------------------------------------------------------- parameter ------------------------------------------------------- Focal Length 42.2 mm f/ratio 1.4 IFOV (1) Cross-track 0.051 deg (0.0008901179185171081 rad) Along-track 0.051 deg (0.0008901179185171081 rad) ------------------------------------------------------- (1) IFOV is approximately computed as total FOV divided by number of pixels: IFOV = 0.051 degrees = 0.0008901179185171081 radians ~ FOV / npixels degrees For horizontal, = 16.74 degrees / 328 = 0.051036585365853655 degrees For vertical, = 12.66 degrees / 248 = 0.051048387096774193 degrees \begindata INS-37200_FOCAL_LENGTH = ( 42.2 ) INS-37200_FOCAL_LENGTH_UNITS = 'mm' INS-37200_F/RATIO = ( 1.4 ) INS-37200_IFOV = ( 0.0008901179185171081, 0.0008901179185171081 ) INS-37200_IFOV_UNITS = 'RADIANS' \begintext Detector Parameters ------------------------------------------------------------------------------ The detector parameters are included in the data section below, taken from [5]: ----------------------------------- parameter ----------------------------------- Pixel Size, micrometers Cross-track [um] 37 Along-track [um] 37 Detector Array Size Cross-track 248 Along-track 328 Detector Array Center Cross-track 124.5 Along-track 164.5 ----------------------------------- The values are given in um for PIXEL_SIZE keywords and in counts for PIXEL_SAMPLES, PIXEL_LINES, and DETECTOR_CENTER keywords. The values of PIXEL_SAMPLES and PIXEL_LINES are equal to the diameter of each filter, in counts. \begindata INS-37200_PIXEL_SIZE = ( 37, 37 ) INS-37200_PIXEL_SIZE_UNITS = 'um' INS-37200_PIXEL_SAMPLES = ( 328 ) INS-37200_PIXEL_LINES = ( 248 ) INS-37200_DETECTOR_CENTER = ( 164.5, 124.5 ) \begintext Wavelength Ranges and Filter Parameters ------------------------------------------------------------------------------ This section contains assignments specifying TIR filter wavelength range and other filter parameters. The following filter data are taken from [4]: ----------------------------------------------------------------------- Channel Band Center, Bandwidth, Quantum Transmittance micrometers micrometers (1) Efficiency (2) ----------------------------------------------------------------------- 10 micrometers 10 4 0.85 0.509 ----------------------------------------------------------------------- (1) The bandwidth is defined in terms of Full Width at Half Peak (FWHP) values, as described in [4]. (2) The transmittance values account for both the optics and the filter. The set of assignments below specifies wavelength center and bandwidth for each optical condition, with units in nanometer for the bandcenter and the bandwidth which are different with the table above. \begindata INS-37200_FILTER_BANDCENTER = ( 10000 ) INS-37200_FILTER_BANDWIDTH = ( 4000 ) INS-37200_FILTER_BAND_UNITS = 'nm' INS-37200_FILTER_QE = ( 0.85 ) INS-37200_FILTER_TRANSMITTANCE = ( 0.509 ) \begintext FOV Definitions ------------------------------------------------------------------------------ This section contains definitions for TIR. These definitions are provided in a format consistent required by the SPICE (CSPICE) function GETFOV (getfov_c). Since the TIR FOV is rectangle 12.66 x 16.74 degrees, looking down the -Z-axis in the Hayabusa2 frame, we have: (Note we are arbitrarily choosing a vector that terminates in the Z=1 plane.) \begindata INS-37200_FOV_FRAME = 'HAYABUSA2_TIR-S' INS-37200_FOV_SHAPE = 'RECTANGLE' INS-37200_BORESIGHT = ( 0.0000000 0.000000 1.000000 ) INS-37200_FOV_CLASS_SPEC = 'ANGLES' INS-37200_FOV_REF_VECTOR = ( 0.0000000 1.000000 0.000000 ) INS-37200_FOV_REF_ANGLE = 6.33 INS-37200_FOV_CROSS_ANGLE = 8.37 INS-37200_FOV_ANGLE_UNITS = 'DEGREES' \begintext Optical Distortion ----------------------------------------------------------------------------- This section provides optical distortion and geometric calibration data for TIR. Simple evaluation test for optical distortion which had been carried out by using a collimator in a laboratory before the launch shows no problem in the optics. Hence, no correction for the optical distortion is considered in image processing. End of IK file.