KPL/IK VMC Instrument kernel =========================================================================== This instrument kernel (I-kernel) contains Venus Express Venus Monitoring Camera (VMC) camera optics, detector, and field-of-view parameters. Version and Date =========================================================================== Version 4.0 -- June 27, 2007 -- Boris Semenov, NAIF/JPL - changed version and ``Version and Date'' section to reflect that IFOV and focal length values were updated based on the 26-April-2007 based on the e-mail from Pedro Russ and added this e-mail to the references section. - filled in (in a truly minimalist way) the ``Instrument Overview'' section - added ``Computing Pixel View Direction for a Given Image Pixel'' section Version 3.0 -- July 12, 2006 -- Klaus-Dieter Matz, DLR - Corrected values for IFOV (due to new calculation method). - Eliminating not applicable variable FOV_ANGULAR_SIZE. Version 2.0 -- April 6, 2006 -- Klaus-Dieter Matz, DLR - New concept of cutting the full image into the separate filters. This leads to different values of CCD_CENTER and images size (i.e. PIXEL_SAMPLES and PIXEL_LINES). - Changing the form of the FOV from circular to polygonal. Version 1.0 -- November 23, 2005 -- Jorge Diaz del Rio, RSSD/ESA Initial release. Version 0.0 -- November 22, 2005 -- Jorge Diaz del Rio, RSSD/ESA Preliminary Version. Pending review from VMC Team. References =========================================================================== 1. ``Kernel Pool Required Reading'', NAIF Document No.____ 2. ``C-kernel Required Reading'', NAIF Document No.____ 3. ``VMC Payload Interface Document, Part-B'' VMC-MPAE-PID-B, Issue 02, Rev a, 01/06/2004 4. Venus Express Frames Definition Kernel (FK), latest version. 5. E-mail from Pedro Russ providing IFOV and focal length values, 26-April-2007. 6. VMC Description on ESA Science & Technology VEX Web Site http://sci.esa.int/science-e/www/object/ index.cfm?fobjectid=33964&fbodylongid=1448 Contact Information ======================================================================== Jorge Diaz del Rio, RSSD/ESA, (31) 71-565-5175, jdiaz@rssd.esa.int 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 VEX instrument ID code, constructed using the spacecraft ID number (-248) followed by the NAIF three digit ID number for VMC main camera base (600) or individual filters (610, 620, 630, 640). These IDs are defined in [4] as follows: Instrument name ID -------------------- ------- VEX_VMC_BASE -248600 VEX_VMC_NIR-1 -248610 VEX_VMC_NIR-2 -248620 VEX_VMC_UV -248630 VEX_VMC_VIS -248640 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 VMC Ultra-Violet (UV) Filter is specified by INS-248630_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. Instrument Overview =========================================================================== From [6]: The Venus Monitoring Camera (VMC) camera consists of one unit that houses the optics, CCD and readout electronics (CRE), digital processing unit (DPU), and power converter (POC). The camera has four separate objective lens systems, each of which images a different, filter selected wavelength range onto a quadrant of a common 1032 x 1024 pixel Charge Coupled Device (CCD) detector. The field of view of the camera is 17.5 degrees (0.3 radians) and the image scale is 0.74 milliradians per pixel. Mounting Alignment =========================================================================== Refer to the latest version of the Venus Express Frames Definition Kernel (FK) [4] for the VMC reference frame definitions and mounting alignment information. Detector Layout =========================================================================== This section provides a diagram illustrating the VMC camera detector layout in the corresponding camera reference frames. The VMC camera comprises a single rectangular CCD detector and it has four different filters. In order to avoid moving parts (filter wheel) the camera is designed so that four objectives (channels) share a single CCD. The position of each filter (channel) on the CCD is shown in the following drawing: Pixel Pixel 1,1 1024,1 \ / \ / ________\ ____________________________________ / ^ | . -^- . : : . -^- . | | | .' |+Yvis : : .' |+Ynir1 | | | / | \: :/ | \ | | |.+Xvis | . +Xnir1 | .| | ||<-----x | ^ |<-----x || | |. +Zvis . | . +Znir1.| | | \ / | :\ / | | | `. VIS .' : |+Yvmc. NIR-1 .' | | |....`.---.'...:...|..:...`.---.'....| | | +Xvmc : | : | 1024 | | <---------X : | px | | : +Zvmc | | |......-^-.....:......:.....-^-......| | | .' |+Yuv. : : .' |+Ynir2 | | | / | \: :/ | \ | | |.+Xuv | . +Xnir2 | .| | ||<-----x | |<-----x || | |. +Zuv . . +Znir2.| | | \ /: :\ / | | | `. UV .' : : `. NIR-2 .' | | |....`.---.'...:......:...`.--- '....| v |____________________________________| --------/: :\ / :<---------------------------------->: \ / : 1024 px : \ Pixel Pixel 1024,1024 1,1024 The diagram above describes the photosensitive area of the CCD. The full CCD is made of 1032x1024 pixels but only 1024x1024 are transferred. Each of image consists of: - 2 dark lines - 1018 photosensitive lines - 4 dark lines Each line consists of: - 6 dummy pixels - 6 dark pixels - 1008 photosensitive pixels - 10 dark pixels - 2 dummy pixels Only the first 1024 pixels of each line will be transferred. Computing Pixel View Direction for a Given Image Pixel =========================================================================== For a pixel in 512x512 pixel image for a given channel, specified by its image coordinates (SAMPLE,LINE), the focal plane coordinates (X,Y) in the corresponding channel reference frame can be computed as follows: X = ( CCD_CENTER(1) - ( SAMPLE_FIRST_PIXEL + SAMPLE ) ) * PIXEL_SIZE Y = ( CCD_CENTER(2) - ( LINE_FIRST_PIXEL + LINE ) ) * PIXEL_SIZE where CCD_CENTER(i) and PIXEL_SIZE are the IK parameters for that channel provided below and LINE_FIRST_PIXEL and SAMPLE_FIRST_PIXEL are parameters from the image label specifying the position of the image's pixel 1,1 in the full 1024x1024 CCD. Note that the formula for computing X does not match the increasing pixel/increasing X coordinate relationship shown on the diagram in the section ``Detector Layout'' above because archived images are flipped about vertical (+Y axis) compared to the CCD output. The pixel view direction vector in the channel's frame can then be constructed using X,Y and the channel's focal length as follows: V = ( X, Y, FOCAL_LENGTH ) Note that this simple approach does not take into account the optical distortion in the camera. Optical Parameters =========================================================================== The following VMC camera first order optical parameters are included in the data section below, taken from [3]: -------------------------------------------------------------------- parameter NIR-1 NIR-2 UV VIS -------------------------------------------------------------------- Focal Length, mm 13.0 13.0 13.0 13.0 f/ratio f/5.0 f/5.0 f/7.0 f/5.0 IFOV, mrad (1) 0.69 0.69 0.69 0.69 -------------------------------------------------------------------- (1) IFOV is computed as the arcus tangens of the pixel size divided by the nominal focal length: Pixel size IFOV = ATAN( -------------- ) Focal length 0.009 mm = ATAN( ---------- ) = 0.69 mrad 13.0 mm Angular size values in the keywords are given in radians. Only one value is provided since the shape of the different filters' Field of View is circular. New values for IFOV (mail from Pedro Russ, 26-April-2007): UV ifov= 0.000692601 rad VIS ifov= 0.000706221 rad NIR ifov= 0.000701960 rad NIR-2 ifov=0.000703716 rad changed FOCAL_LENGTH accordingly, PIXEL_SIZE is unchanged \begindata INS-248610_FOCAL_LENGTH = ( 12.82124 ) INS-248610_F/RATIO = ( 5.0 ) INS-248610_IFOV = ( 0.000701960 ) INS-248620_FOCAL_LENGTH = ( 12.78925 ) INS-248620_F/RATIO = ( 5.0 ) INS-248620_IFOV = ( 0.000703716 ) INS-248630_FOCAL_LENGTH = ( 12.9945 ) INS-248630_F/RATIO = ( 7.0 ) INS-248630_IFOV = ( 0.000692601 ) INS-248640_FOCAL_LENGTH = ( 12.7439 ) INS-248640_F/RATIO = ( 5.0 ) INS-248640_IFOV = ( 0.000706221 ) \begintext Detector CCD Parameters =========================================================================== The VMC detector parameters are included in the data section below, taken from [3]: ----------------------------------------------------------------- parameter NIR-1 NIR-2 UV VIS ----------------------------------------------------------------- Pixel Size, microns Cross-track 9.0 9.0 9.0 9.0 Along-track 9.0 9.0 9.0 9.0 Detector Array Size (1) Cross-track 512 512 512 512 Along-track 512 512 512 512 Detector Array Center (2) Cross-track 256.5 256.5 768.5 768.5 Along-track 256.5 768.5 768.5 256.5 ----------------------------------------------------------------- (1) Each of the VMC filters has a irregular field-of-view, resulting from the combination of the circular illumination of the CCD with a quadratic mask on the CCD. The polygon describing the form of the FOV can be found below. (2) The VMC photosensitive detector is a 1024x1024 CCD. The four filters share the CCD and each one is centered in one of the CCD quadrants. The center of each sensor is given in absolute pixel numbering on the full ccd. The values are given in microns for PIXEL_SIZE keywords and in counts for PIXEL_SAMPLES, PIXEL_LINES, and CENTER keywords. The values of PIXEL_SAMPLES and PIXEL_LINES are equal to the diameter of each filter, in counts. \begindata INS-248610_PIXEL_SIZE = ( 9.0, 9.0 ) INS-248610_PIXEL_SAMPLES = ( 512 ) INS-248610_PIXEL_LINES = ( 512 ) INS-248610_CCD_CENTER = ( 256.5, 256.5 ) INS-248620_PIXEL_SIZE = ( 9.0, 9.0 ) INS-248620_PIXEL_SAMPLES = ( 512 ) INS-248620_PIXEL_LINES = ( 512 ) INS-248620_CCD_CENTER = ( 256.5, 768.5 ) INS-248630_PIXEL_SIZE = ( 9.0, 9.0 ) INS-248630_PIXEL_SAMPLES = ( 512 ) INS-248630_PIXEL_LINES = ( 512 ) INS-248630_CCD_CENTER = ( 768.5, 768.5 ) INS-248640_PIXEL_SIZE = ( 9.0, 9.0 ) INS-248640_PIXEL_SAMPLES = ( 512 ) INS-248640_PIXEL_LINES = ( 512 ) INS-248640_CCD_CENTER = ( 768.5, 256.5 ) \begintext Wavelength Ranges and Filter Parameters =========================================================================== This section contains assignments specifying VMC filters wavelength range and other filter parameters. The following filter data are taken from [3]: ------------------------------------------------------------------- Detector Band Center, Bandwidth, Quantum Trans- nanometers nanometers (1) Efficiency mittance (2) ------------------------------------------------------------------- NIR-1 935 70 0.2 0.81 NIR-2 1010 20 0.1 0.81 UV 365 40 0.25 0.36 VIS 513 50 0.35 0.45 ------------------------------------------------------------------- (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 filter, with units the same as in the table above. \begindata INS-248610_FILTER_BANDCENTER = ( 935 ) INS-248610_FILTER_BANDWIDTH = ( 70 ) INS-248610_FILTER_QE = ( 0.2 ) INS-248610_FILTER_TRANSMITTANCE = ( 0.81 ) INS-248620_FILTER_BANDCENTER = ( 1010 ) INS-248620_FILTER_BANDWIDTH = ( 20 ) INS-248620_FILTER_QE = ( 0.1 ) INS-248620_FILTER_TRANSMITTANCE = ( 0.81 ) INS-248630_FILTER_BANDCENTER = ( 365 ) INS-248630_FILTER_BANDWIDTH = ( 40 ) INS-248630_FILTER_QE = ( 0.25 ) INS-248630_FILTER_TRANSMITTANCE = ( 0.36 ) INS-248640_FILTER_BANDCENTER = ( 513 ) INS-248640_FILTER_BANDWIDTH = ( 50 ) INS-248640_FILTER_QE = ( 0.35 ) INS-248640_FILTER_TRANSMITTANCE = ( 0.45 ) \begintext FOV Definitions =========================================================================== This section contains definitions for each of the VMC filters FOV. These definitions are provided in a format consistent required by the SPICE (CSPICE) function GETFOV (getfov_c). The set of assignments in the data section below defines each of the VMC filters FOV with respect to its frame: Filter Name Frame ------------- ----------------- NIR-1 VEX_VMC_NIR-1 NIR-2 VEX_VMC_NIR-2 UV VEX_VMC_UV VIS VEX_VMC_VIS Each of the FOVs is a cone with a half angle of 0.15 radians. For each of the frames, the boresight vector, along the +Z axis of the frame, was scaled to be equal to the focal length. The cross-reference vector is a unit vector along the +X axis of the frame. \begindata INS-248610_FOV_FRAME = 'VEX_VMC_NIR-1' INS-248610_FOV_SHAPE = 'POLYGON' INS-248610_BORESIGHT = ( 0.0 0.0 13.0 ) INS-248610_FOV_BOUNDARY_CORNERS = ( 1.426 2.164 13.000 -0.841 2.236 13.000 -1.867 1.183 13.000 -1.921 -0.553 13.000 -0.742 -1.921 13.000 1.246 -1.993 13.000 2.218 -1.021 13.000 2.236 1.309 13.000 ) INS-248620_FOV_FRAME = 'VEX_VMC_NIR-2' INS-248620_FOV_SHAPE = 'POLYGON' INS-248620_BORESIGHT = ( 0.0 0.0 13.0 ) INS-248620_FOV_BOUNDARY_CORNERS = ( 1.435 1.804 13.000 -0.508 1.876 13.000 -0.922 1.813 13.000 -1.993 0.697 13.000 -2.074 -1.399 13.000 -1.372 -2.272 13.000 1.534 -2.272 13.000 2.092 -1.714 13.000 2.164 1.048 13.000 ) INS-248630_FOV_FRAME = 'VEX_VMC_UV' INS-248630_FOV_SHAPE = 'POLYGON' INS-248630_BORESIGHT = ( 0.0 0.0 13.0 ) INS-248630_FOV_BOUNDARY_CORNERS = ( 0.688 1.903 13.000 -1.201 1.966 13.000 -2.182 1.192 13.000 -2.201 -1.570 13.000 -1.552 -2.201 13.000 0.913 -2.254 13.000 1.714 -1.489 13.000 1.768 0.823 13.000 ) INS-248640_FOV_FRAME = 'VEX_VMC_VIS' INS-248640_FOV_SHAPE = 'POLYGON' INS-248640_BORESIGHT = ( 0.0 0.0 13.0 ) INS-248640_FOV_BOUNDARY_CORNERS = ( 0.877 2.272 13.000 -1.237 2.272 13.000 -2.201 1.354 13.000 -2.201 -0.904 13.000 -1.399 -1.795 13.000 0.652 -1.840 13.000 1.813 -0.661 13.000 1.867 1.102 13.000 ) \begintext Optical Distortion =========================================================================== This section provides optical distortion and geometric calibration data for the VMC camera. The optical distortion for the VMC camera was not available at the time when this version of the IK was released. Platform ID =========================================================================== This number is the NAIF instrument ID of the platform on which the camera is mounted. This platform is the spacecraft. Each of the filters is rigidly mounted on the instrument base. \begindata INS-248600_PLATFORM_ID = ( -248000 ) INS-248610_PLATFORM_ID = ( -248600 ) INS-248620_PLATFORM_ID = ( -248600 ) INS-248630_PLATFORM_ID = ( -248600 ) INS-248640_PLATFORM_ID = ( -248600 ) \begintext