KPL/IK GEM Instrument Kernel =========================================================================== This instrument kernel (I-kernel) contains the mounting alignment, FOV geometry information and internal parameter values for the Genesis Electron Monitor (GEM) Instrument. Version and Date -------------------------------------------------------- Version 1.0 -- July 6, 2000 -- Boris Semenov, NAIF/JPL Initial Release. References -------------------------------------------------------- 1. ``Kernel Pool Required Reading'' 2. Genesis Frame Definitions Kernel, latest version. 3. Genesis Misson Plan (Doc.# GN-61000-202), October 1, 1999 4. LANL IOM "Alignment of Genesis Monitors", June 20, 2000 5. GEM Design/Measured CEM Geometry Chart, by LANL, June 2000 Implementation Notes -------------------------------------------------------- This file is used by the SPICE system as follows: programs that make use of this I-kernel must `load' the kernel, normally during program initialization. Loading the kernel associates data items with their names in a data structure called the `kernel pool'. The SPICELIB routine LDPOOL loads a kernel file into the pool as shown below. CALL LDPOOL ( I_kernel_name ) In order for a program or subroutine to extract data from the pool, the SPICELIB routines GDPOOL and GIPOOL are used. See [4] for more details. This file was created and can be updated with a text editor or word processor. Naming Conventions -------------------------------------------------------- All names referencing values in this I-kernel start with the characters `INS' followed by the NAIF GNS spacecraft ID number (-47) followed by the NAIF three digit GEM instrument reference number (100) or GEM CEM reference number (101...107). The remainder of the name is an underscore character followed by the unique name of the data item. For example, the GEM CEM #1 FOV shape is specified by INS-47101_FOV_SHAPE The upper bound on the length of the name of any data item is 32 characters. If the same item is included in more then one file, or if the same item appears more than once within a single file, the latest value supersedes any earlier values. GEM description -------------------------------------------------------- From [?]: [to be added] GEM Instrument Performance Parameters -------------------------------------------------------- Nominal GEM Instrument Performance Parameters as provided in [5]: -------------------------- -------------- ---------------- parameter value units -------------------------- -------------- ---------------- Analyzer K 4.2 Energy/Volts Energy resolution 13 % - FWHM Energy range 1 .. 903 eV (*) Azimuthal Angle Resolution +/- 9 @ 0deg deg - FWHM +/-14 @73deg (*) Azimuthal Angle Range 360 deg (provided by s/c rotation) (*) Polar Angle Resolution 19.5 deg - FWHM (*) Polar Angle Range +/-73 deg (*) Centers of Polar pixels 0 deg +/- 21 +/- 42 +/- 63 -------------------------- -------------- ---------------- (*) these parameters are incorporated into the CEM frame and FOV definitions. These values are provided in the keywords below in the same units as in the table above: \begindata INS-47100_ANALYZER_K = 4.2 INS-47100_ENERGY_RESOLUTION = 13 INS-47100_ENERGY_RANGE = ( 1, 903 ) \begintext GEM Mounting alignment -------------------------------------------------------- GEM mounting alignment is incorporated into the GEM frame definition provided in the Genesis Frames definition kernel [2]. GEM FOV Definition -------------------------------------------------------- The orientation of the GEM FOV with respect to the GEM Frame (see [2]) is shown on the diagram below: GEM -Y side view: ----------------- (+polar) . ^ +X Spacecraft cem7 . ^ +Xgem | (spin axis) . . | | cem6 `. . |_________ GEM Sensor | . `. . || | | cem5 `. `. . || | ` . `. `..|| | cem4 +Zgem <-----x | . ' .' .'.| +Ygem (into page ) cem3 .' .' . | | ' .' . |__________|______________ cem2 .' . | | GEM Mounting Plate ' . _|_______________________|_____ cem1 . | / / / / / / / / / / / / / / / . |/ / Spacecraft Deck / / / / / / (-polar) GEM FOV Polar Range +/-73 deg GEM +X side view: ----------------- +Ygem ^ | | Spacecraft Deck (-azimuth) | | ' . | __|____________________ ' . ||________ | +Zgem <--------o | | ^ +Ysc . ' | +Xgem | GEM Sensor | \ . ' | | | \ (+azimuth) | | | o +Xsc (spin axis, | | | / out of page) GEM FOV | | | / Azimuthal Range |__________| | V +Zsc 9..13 deg |_______________________| | GEM Mounting Plate | | Because the individual GEM CEM FOVs have different forms and sizes, combined GEM FOV cannot be accurately approximated by a simple shape. Should a need in such combined FOV definition arise, it can be made by putting together, in the right order, the edges of the individual CEM FOVs rotated to the GNS_GEM frame to create a complex polygonal FOV defined by 28 vertices (7 CEMs x 4 vertices each.) The boresight of the combined GEM FOV is the same as the boresight of the CEM #4, i.e. along +Z axis of the GNS_GEM and GNS_GEM_CEM4 frames. GEM CEM FOV Definitions -------------------------------------------------------- The FOV of a particular GEM CEM is defined with respect to that CEM's frame (see [2]) with FOV boresight along +Z axis of the frame. Nominally, all CEM FOVs have angular size of 19.5 degrees in polar direction (in CEM frame XZ plane.) The azimuthal size (in CEM frame YZ plane) depends on the position of the CEM in the array and nominally varies from 9 degrees (at 0 degrees polar, the center of the CEM #4 FOV) to 14 degrees (at 73 degrees polar, the farthest edge of the CEM #1 & CEM #7 FOV.) Using simple linear approximation, the azimuthal angular sizes at the the edges of the individual CEM FOVs are: CEM # Edge Polar Angle, deg Azimuthal Size, deg ---------- ----------------------- ---------------------- CEM #1 -63 - 19.5/2 = -72.75 12.986 -63 + 19.5/2 = -53.25 11.918 CEM #2 -42 - 19.5/2 = -51.75 11.836 -42 + 19.5/2 = -32.25 10.767 CEM #3 -21 - 19.5/2 = -30.75 10.685 -21 + 19.5/2 = -11.25 9.616 CEM #4 0 - 19.5/2 = -9.75 9.534 0 + 19.5/2 = +9.75 9.534 CEM #5 +21 - 19.5/2 = +11.25 9.616 +21 + 19.5/2 = +30.75 10.685 CEM #6 +42 - 19.5/2 = +32.25 10.767 +42 + 19.5/2 = +51.75 11.836 CEM #7 +63 - 19.5/2 = +53.25 11.918 +63 + 19.5/2 = +72.75 12.986 All CEM FOVS are defined below as four-vertex polygons with vertices computed using these angular size. The sets of keywords defining CEM FOVs are consistent with the SPICELIB/cspice's GETFOV/getfoc_c interface. \begindata INS-47101_FOV_FRAME = 'GNS_GEM_CEM1' INS-47101_FOV_SHAPE = 'POLYGON' INS-47101_BORESIGHT = ( 0.0 0.0 1.0 ) INS-47101_FOV_BOUNDARY_CORNERS = ( .171831426830 .104380799563 1.0 -.171831426830 .113811851008 1.0 -.171831426830 -.113811851008 1.0 .171831426830 -.104380799563 1.0 ) INS-47102_FOV_FRAME = 'GNS_GEM_CEM2' INS-47102_FOV_SHAPE = 'POLYGON' INS-47102_BORESIGHT = ( 0.0 0.0 1.0 ) INS-47102_FOV_BOUNDARY_CORNERS = ( .171831426830 .094237286511 1.0 -.171831426830 .103657471924 1.0 -.171831426830 -.103657471924 1.0 .171831426830 -.094237286511 1.0 ) INS-47103_FOV_FRAME = 'GNS_GEM_CEM3' INS-47103_FOV_SHAPE = 'POLYGON' INS-47103_BORESIGHT = ( 0.0 0.0 1.0 ) INS-47103_FOV_BOUNDARY_CORNERS = ( .171831426830 .084112958714 1.0 -.171831426830 .093515395204 1.0 -.171831426830 -.093515395204 1.0 .171831426830 -.084112958714 1.0 ) INS-47104_FOV_FRAME = 'GNS_GEM_CEM4' INS-47104_FOV_SHAPE = 'POLYGON' INS-47104_BORESIGHT = ( 0.0 0.0 1.0 ) INS-47104_FOV_BOUNDARY_CORNERS = ( .171831426830 .083392354214 1.0 -.171831426830 .083392354214 1.0 -.171831426830 -.083392354214 1.0 .171831426830 -.083392354214 1.0 ) INS-47105_FOV_FRAME = 'GNS_GEM_CEM5' INS-47105_FOV_SHAPE = 'POLYGON' INS-47105_BORESIGHT = ( 0.0 0.0 1.0 ) INS-47105_FOV_BOUNDARY_CORNERS = ( .171831426830 .093515395204 1.0 -.171831426830 .084112958714 1.0 -.171831426830 -.084112958714 1.0 .171831426830 -.093515395204 1.0 ) INS-47106_FOV_FRAME = 'GNS_GEM_CEM6' INS-47106_FOV_SHAPE = 'POLYGON' INS-47106_BORESIGHT = ( 0.0 0.0 1.0 ) INS-47106_FOV_BOUNDARY_CORNERS = ( .171831426830 .103657471924 1.0 -.171831426830 .094237286511 1.0 -.171831426830 -.094237286511 1.0 .171831426830 -.103657471924 1.0 ) INS-47107_FOV_FRAME = 'GNS_GEM_CEM7' INS-47107_FOV_SHAPE = 'POLYGON' INS-47107_BORESIGHT = ( 0.0 0.0 1.0 ) INS-47107_FOV_BOUNDARY_CORNERS = ( .171831426830 .113811851008 1.0 -.171831426830 .104380799563 1.0 -.171831426830 -.104380799563 1.0 .171831426830 -.113811851008 1.0 ) \begintext Platform ID -------------------------------------------------------- The GEM in mounted on the GNS spacecraft deck. Therefore the value in the keyword below is -47000. \begindata INS-47100_PLATFORM_ID = ( -47000 ) \begintext