KPL/IK Venus Climate Orbiter Akatsuki LIR Instrument kernel ============================================================================== Version and Date ============================================================================== Version 11 -- Mar 14, 2022 Shin-ya Murakami, ISAS/JAXA - Added description for new dead pixel. - Updated title of the references. - Updated contact information. - Removed inappropriate description in the Detector Parameters section. - Improved descriptions in the FOV Definitions section Version 10 -- Mar 18, 2020 Added description for new dead pixel. Applied some cosmetic changes. Version 09 -- Oct 16, 2018 Fixed typos and some cosmetic changes. Version 08 -- Jun 16, 2017 Add new Frames and Image Coordinates section, and notations of axes in Detector Layout section has been simplified. Version 07 -- May 16, 2017 Description of FOV in Overview has been corrected. Detector Layout has been revised. Version 06 -- Nov 15, 2016 Added _PIC axes to diagram Version 05 -- Sep 28, 2016 All description has been reviewed and revised by T. Fukuhara. Version 04 -- Oct 13, 2015 Version 03 -- Oct 06, 2015 Version 02 -- FEB 25, 2015 Version 01 -- FEB 12, 2015 Version 00 -- SEPT 10, 2014 Version beta-04 -- AUG 04, 2014 Version beta-03 -- JULY 29, 2014 Version beta-02 -- JUNE 08, 2013 Version beta-01 -- SEPT 17, 2011 Version beta-00 -- JUNE 14, 2009 References ============================================================================== 1. ``SPICE Kernel Required Reading'', https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/kernel.html 2. ``C-Kernel Required Reading'', https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/ck.html 3. Fukuhara et al. (2011), LIR: Longwave Infrared Camera onboard the Venus orbiter Akatsuki, Earth Planets Space, 63, 1009-1018. DOI: 10.5047/eps.2011.06.019 4. Venus Climate Orbiter Frames Kernel (FK), latest version Contact Information ============================================================================== Taguchi Makoto, Rikkyo University, taguchi@rikkyo.ac.jp Toru Kouyama, National Institute of Advanced Industrial Science and Technology, t.kouyama@aist.go.jp 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 Venus Climate Orbiter (VCO, also known as PLANET-C and AKATSUKI) instrument ID code, constructed using the spacecraft ID number (-5) followed by the NAIF three digit ID number for LIR main camera base (500) or individual channels (510, 520, 530). These IDs are defined in [4] as follows: LIR names/IDs: Instrument name ID -------------------- ------- VCO_LIR_BASE -5500 VCO_LIR_PIC -5510 VCO_LIR_OPN -5520 VCO_LIR_SHT -5530 The remainder of the keyword is an underscore character followed by the unique name of the data item. For example, the focal length of the LIR PIC is specified by INS-5510_FOCAL_LENGTH The upper bound on the length of all keywords is 32 characters. If a keyword is included in more then one file, or if the same keyword appears more than once within a single file, the last assignment supersedes any earlier assignments. Overview ============================================================================== The Longwave Infrared camera (LIR) detects thermal emission of both day and night-side from the top of sulfur dioxide cloud with wavelength region of 8 - 12 um. LIR mounts a detector called the uncooled micro-bolometer array (UMBA) in order to remove heavy cryogenic apparatus which is commonly used for infrared detectors. Hence, temperature of detector in LIR can be estimated to room temperature (it is set to 313 K in case of LIR). LIR consists of a sensor unit (LIR-S) and an external power supply unit (LIR-AE). The sensor unit contains optics, a mechanical shutter, an image sensor and its drive circuit. The optics consists of three Germanium lenses with the F-number of 1.4 and focal length of 42 mm. A band-pass filter for the wavelength region described above is inserted at the pupil position of the optics and a mechanical shutter is positioned just in front of the UMBA. A baffle is configured outside of the spacecraft. The UMBA has active pixels of 328 x 248 with pixel size of 37 um. Hence, LIR attains spatial resolution of 0.05 degrees with a field-of-view of 16 x 12 degrees in the XZ and XY planes of the spacecraft coordinate system, respectively. The UMBA mounted to LIR includes the on-chip fixed pattern noise (OFPN). They are partly corrected in the internal analog circuit by calibration data acquired beforehand, however, they still remain in images. In order to cancel the OFPN completely, LIR acquires both target and shutter image sequentially, and the shutter image is subtracted from the target image by the digital electronics (DE) on the spacecraft. DE can accumulate LIR images in order to improve signal to noise ratio. Firstly, several tens of target and shutter images are accumulated independently within few seconds. Secondly, several tens of the subtracted images are accumulated within several minutes. The most suitable number of the first accumulation "m" = 32 and second accumulation "n" = 32 have been estimated respectively in laboratory experiment before the launch. These parameters are nominally set to observation programs on the spacecraft. In addition, "m = 1 and n = 1" and "m = 32 and n = 1" are also prepared for specified observations. The former is used for fundamental checkout, and the latter is used for close-up observation at periapsis in which observation period should be as short as possible to avoid blurring. LIR image is converted to brightness temperature on the ground processing by using reference tables which has been acquired before the launch. Temperature range LIR can detect is optimized to typical cloud top temperature of ~230 K. LIR attains the noise equivalent temperature difference (NETD) of ~0.3 K, which is consistent with the cloud height difference of a few hundred meters. Further information is described in [3]. Mounting Alignment ============================================================================== Refer to the latest version of Venus Climate Orbiter Frames Kernel (FK) [4] for the LIR reference frame definitions and mounting alignment information. Frames and Image Coordinates ============================================================================== This section provides the relationship between frames and image coordinates. Notation of the axes -------------------- o axis into the page x axis out of the page +Xsc, +Ysc and +Zsc +X, +Y and +Z axes of the spacecraft frame. +Xlirb, +Ylirb and +Zlirb +X, +Y and +Z axes of the LIR base frame. +X_PIC, +Y_PIC and +Z_PIC +X, +Y and +Z axes of the LIR PIC channel frame. +Xsc_proj, +Ysc_proj, +Zsc_proj, +Xlirb_proj, +Ylirb_proj, +Zlirb_proj, +X_PIC_proj, +Y_PIC_proj and +Z_PIC_proj +Xsc, +Ysc, +Zsc, +Xlirb, +Ylirb, +Zlirb, +X_PIC, +Y_PIC and +Z_PIC axes projected onto the image coordinate, +Ximg_fliprot and +Yimg_fliprot. +Ximg_lir_raw and +Yimg_lir_raw axes of the original image coordinate for the image sent down from the spacecraft. +Ximg_fliprot and +Yimg_fliprot axes of the image coordinate after flip and rotation of original image to direct +Ysc_proj become upward in the coordinate with the origin at lower-left corner of the image. For LIR images, the actual operation of flip and rotation is just flipping original image vertically. Relationship between Spacecraft frame and LIR base frame -------------------------------------------------------- The diagrams below are the relationship between spacecraft frame and LIR base frame. S/C LIR +Ysc +Zlirb, +Y_PIC ^ ^ | | | | | | x---------> +Zsc o---------> +Xlirb, +X_PIC +Xsc -Ylirb, +Z_PIC Requirement for image's orientation ----------------------------------- Let us suppose that upward of the level 1b image directs +Ysc, and that image has axes, +Ximg_fliprot and +Yimg_fliprot as follows. +Ysc_proj, +Yimg_fliprot ^ | | | x---------> -Zsc_proj, +Ximg_fliprot -Xsc_proj An object to be taken is inside the page. Relationships of frames and image coordinates for LIR ----------------------------------------------------- 1. An optical image of the object at outside of the camera system An optical image of the object marked with +, =, -, and *, is located outside of the camera system. View from -Xsc side to +Xsc side, View from +Xsc side to -Xsc side, i.e., view from the frontside of i.e., view from the backside of the detector the detector +Ysc, +Zlirb, +Y_PIC +Ysc, +Zlirb, +Y_PIC ^ ^ | | -- | ++ ++ | -- | +Zsc, +Xlirb, | -Zsc, -Xlirb, o---------> +X_PIC x---------> -X_PIC -Xsc, -Ylirb, -Xsc, -Ylirb, +Z_PIC +Z_PIC ** == == ** 2. An optical image of the object on the detector Let us consider the optics system rotates 180 degrees of an optical image. On the detector, an optical image of the object is projected onto the detector as below diagrams: View from -Xsc side to +Xsc side, View from +Xsc side to -Xsc side, i.e., view from the frontside of i.e., view from the backside of the detector the detector -Ysc_proj, -Zlirb_proj, -Ysc_proj, -Zlirb_proj, ^ -Y_PIC_proj ^ -Y_PIC_proj | | == | ** ** | == | -Zsc_proj, | +Zsc_proj, o---------> -Xlirb_proj, x---------> +Xlirb_proj, -Xsc, -Ylirb, -X_PIC_proj -Xsc, -Ylirb, +X_PIC_proj +Z_PIC +Z_PIC ++ -- -- ++ 3. Orientation of the optical image of the object on the original image (detector) coordinate Add the original image (detector) coordinate. View from -Xsc side to +Xsc side, View from +Xsc side to -Xsc side, i.e., view from the frontside of i.e., view from the backside of the detector the detector -Ysc_proj, -Zlirb_proj, -Ysc_proj, -Zlirb_proj, -Y_PIC_proj, -Y_PIC_proj, ^ +Yimg_lir_raw ^ +Yimg_lir_raw | | == | ** ** | == | -Zsc_proj, | +Zsc_proj, o---------> -Xlirb_proj, x---------> +Xlirb_proj, -Xsc, -Ylirb, -X_PIC_proj, -Xsc, -Ylirb, +X_PIC_proj, +Z_PIC +Ximg_lir_raw +Z_PIC -Ximg_lir_raw ++ -- -- ++ 4. Arrange coordinates Flip and rotate to make +Ximg_lir_raw and +Yimg_lir_raw become nominal (level 1a image). -Ysc_proj, -Zlirb_proj, ^ -Y_PIC_proj, +Yimg_lir_raw | == | ** | -Zsc_proj, x---------> -Xlirb_proj, -Xsc, -Ylirb, -X_PIC_proj, +Z_PIC +Ximg_lir_raw ++ -- 5. flip and rotate to make +Ysc_proj upward Flip vertically to obtain level 1b/2b image. +Ysc_proj, +Zlirb_proj, ^ +Y_PIC_proj, -Yimg_lir_raw, +Yimg_fliprot | ++ | -- | -Zsc_proj, x---------> -Xlirb_proj, -Xsc, -Ylirb, -X_PIC_proj, +Z_PIC +Ximg_lir_raw, +Ximg_fliprot == ** Note that -Xsc, -Ylirb, +Z_PIC, -Xsc_proj, -Ylirb_proj and +Z_PIC_proj are same direction, so the (+Xsc_proj, +Ysc_proj, +Zsc_proj), the (+Xlirb_proj, +Ylirb_proj, +Zlirb_proj) and the (+X_PIC_proj, +Y_PIC_proj, +Z_PIC_proj) become right-handed coordinates. Detector Layout ============================================================================== This section provides a diagram illustrating LIR detector layout in the corresponding camera reference frames. Notations of the axes are same as in the ``Frames and Image Coordinates'' section. The relashionship between the axes of the VCO_LIR_BASE frame projected onto the detector and the image coordinate look like this: ^ -Yimg_lir_raw, ^ +Ysc_proj, | +Yimg_fliprot | +Zlirb_proj, | | +Y_PIC_proj +-------------------|-------------------+ ( 1,248) | (328,248) ^ | | | | | | | 248 pixels | | | | | | | | | x-------------------------------> -Zsc_proj, | -Xsc, -Ylirb, and +Z_PIC | | -Xlirb_proj, | are into the page | | -X_PIC_proj | | | | | | | | v o---------------------------------------+-----------> +Ximg_lir_raw, ( 1, 1) (328, 1) +Ximg_fliprot <---------------328 pixels------------> The four tuples of numbers (x,y) represent the position in the image coordinate after the flip and the rotation. The order of data line is (1,1), ..., (328,1), (1,2), ..., (328,2), ..., (328,248). Known dead pixels are listed below. They contain scientifically invalid values. Tuple of numbers (x,y) in the ``position'' column is position in the image coordinate after the flip and the rotation, same as the above. position when it became dead pixel ---------- ----------------------------- ( 81, 215) before the launch, 2010-05-20 (185, 143) before the launch, 2010-05-20 (200, 68) before the launch, 2010-05-20 (127, 55) before the launch, 2010-05-20 (216, 57) 2019-12-21T21:00:00 UTC ( 86, 56) 2021-01-29T18:00:00 UTC ( 86, 57) 2021-01-29T18:00:00 UTC (325, 77) 2021-10-28T19:00:00 UTC \begindata INS-5510_START_OF_PIXEL = ( 1, 1 ) INS-5510_END_OF_PIXEL = ( 328, 248 ) INS-5520_START_OF_PIXEL = ( 1, 1 ) INS-5520_END_OF_PIXEL = ( 328, 248 ) INS-5530_START_OF_PIXEL = ( 1, 1 ) INS-5530_END_OF_PIXEL = ( 328, 248 ) \begintext Optical Parameters ============================================================================== LIR first order optical parameters are included in the data section below, taken from [3]: ----------------------------------------------- parameter ----------------------------------------------- Focal Length 42.2 mm f/ratio 1.4 IFOV (1) Cross-track 0.05 deg (0.000876777 rad) Along-track 0.05 deg (0.000876777 rad) ----------------------------------------------- (1) IFOV is computed as the arcus tangens of the pixel size divided by the nominal focal length: Pixel size IFOV = ATAN( -------------- ) rad Focal length where it is typical parameter for center of image. \begindata INS-5510_FOCAL_LENGTH = ( 42.2 ) INS-5510_FOCAL_LENGTH_UNITS = 'mm' INS-5510_F/RATIO = ( 1.4 ) INS-5510_IFOV = ( 0.000876777, 0.000876777 ) INS-5510_IFOV_UNITS = 'RADIANS' INS-5520_FOCAL_LENGTH = ( 42.2 ) INS-5520_FOCAL_LENGTH_UNITS = 'mm' INS-5520_F/RATIO = ( 1.4 ) INS-5520_IFOV = ( 0.000876777, 0.000876777 ) INS-5520_IFOV_UNITS = 'RADIANS' INS-5530_FOCAL_LENGTH = ( 42.2 ) INS-5530_FOCAL_LENGTH_UNITS = 'mm' INS-5530_F/RATIO = ( 1.4 ) INS-5530_IFOV = ( 0.000876777, 0.000876777 ) INS-5530_IFOV_UNITS = 'RADIANS' \begintext Detector Parameters ============================================================================== The detector parameters are included in the data section below, taken from [3]: ----------------------------------- 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 CENTER keywords. \begindata INS-5510_PIXEL_SIZE = ( 37, 37 ) INS-5510_PIXEL_SIZE_UNITS = 'um' INS-5510_PIXEL_SAMPLES = ( 328 ) INS-5510_PIXEL_LINES = ( 248 ) INS-5510_DETECTOR_CENTER = ( 164.5, 124.5 ) INS-5520_PIXEL_SIZE = ( 37, 37 ) INS-5520_PIXEL_SIZE_UNITS = 'um' INS-5520_PIXEL_SAMPLES = ( 328 ) INS-5520_PIXEL_LINES = ( 248 ) INS-5520_DETECTOR_CENTER = ( 164.5, 124.5 ) INS-5530_PIXEL_SIZE = ( 37, 37 ) INS-5530_PIXEL_SIZE_UNITS = 'um' INS-5530_PIXEL_SAMPLES = ( 328 ) INS-5530_PIXEL_LINES = ( 248 ) INS-5530_DETECTOR_CENTER = ( 164.5, 124.5 ) \begintext Wavelength Ranges and Filter Parameters ============================================================================== This section contains assignments specifying LIR filter wavelength range and other filter parameters. The following filter data are taken from [3]: ----------------------------------------------------------------------- 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 [3]. (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 the same as in the table above. \begindata INS-5510_FILTER_BANDCENTER = ( 10000 ) INS-5510_FILTER_BANDWIDTH = ( 4000 ) INS-5510_FILTER_BAND_UNITS = 'nm' INS-5510_FILTER_QE = ( 0.85 ) INS-5510_FILTER_TRANSMITTANCE = ( 0.509 ) INS-5520_FILTER_BANDCENTER = ( 10000 ) INS-5520_FILTER_BANDWIDTH = ( 4000 ) INS-5520_FILTER_BAND_UNITS = 'nm' INS-5520_FILTER_QE = ( 0.85 ) INS-5520_FILTER_TRANSMITTANCE = ( 0.509 ) INS-5530_FILTER_BANDCENTER = ( 10000 ) INS-5530_FILTER_BANDWIDTH = ( 4000 ) INS-5530_FILTER_BAND_UNITS = 'nm' INS-5530_FILTER_QE = ( 0.85 ) INS-5530_FILTER_TRANSMITTANCE = ( 0 ) \begintext FOV Definitions ============================================================================== This section contains definitions for LIR's FOV. The channel names and associated frames are tabulated below: Channel Name Frame ------------- ----------------- PIC VCO_LIR_PIC OPN VCO_LIR_OPN SHT VCO_LIR_SHT Note that all channels have same FOVs. Horizontal half angle REF_ANGLE and the vertical half angle CROSS_ANGLE of the FOV is calculated as follows: Pixel size REF_ANGLE = ATAN( -------------- * PIXEL_SAMPLE / 2 ) Focal length 0.037 mm = ATAN( -------------- * 328 / 2 ) = 0.142812574 rad 42.2 mm Pixel size CROSS_ANGLE = ATAN( -------------- * PIXEL_LINES / 2 ) Focal length 0.037 mm = ATAN( -------------- * 248 / 2 ) = 0.108295029 rad 42.2 mm \begindata INS-5510_FOV_FRAME = 'VCO_LIR_PIC' INS-5510_FOV_SHAPE = 'RECTANGLE' INS-5510_BORESIGHT = ( 0.0 0.0 42.2 ) INS-5510_FOV_CLASS_SPEC = 'ANGLES' INS-5510_FOV_REF_VECTOR = ( 0.0 1.0 0.0 ) INS-5510_FOV_REF_ANGLE = 0.142812574 INS-5510_FOV_CROSS_ANGLE = 0.108295029 INS-5510_FOV_ANGLE_UNITS = 'RADIANS' INS-5520_FOV_FRAME = 'VCO_LIR_OPN' INS-5520_FOV_SHAPE = 'RECTANGLE' INS-5520_BORESIGHT = ( 0.0 0.0 42.2 ) INS-5520_FOV_CLASS_SPEC = 'ANGLES' INS-5520_FOV_REF_VECTOR = ( 0.0 1.0 0.0 ) INS-5520_FOV_REF_ANGLE = 0.142812574 INS-5520_FOV_CROSS_ANGLE = 0.108295029 INS-5520_FOV_ANGLE_UNITS = 'RADIANS' INS-5530_FOV_FRAME = 'VCO_LIR_SHT' INS-5530_FOV_SHAPE = 'RECTANGLE' INS-5530_BORESIGHT = ( 0.0 0.0 42.2 ) INS-5530_FOV_CLASS_SPEC = 'ANGLES' INS-5530_FOV_REF_VECTOR = ( 0.0 1.0 0.0 ) INS-5530_FOV_REF_ANGLE = 0.142812574 INS-5530_FOV_CROSS_ANGLE = 0.108295029 INS-5530_FOV_ANGLE_UNITS = 'RADIANS' \begintext Optical Distortion ============================================================================= This section provides optical distortion and geometric calibration data for LIR. Optical distortion of LIR has been designed within 0.1%. Simple evaluation test which has 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. EOF