DATA_OBJECT_TYPE = SPICE_I-KERNEL MISSION_ID = 1 SPACECRAFT_NAME = GALILEO SPACECRAFT_NUMBER = 77 INSTRUMENT_ID = 25 PROCESS_TIME = 1990-11-12T12:00:00 EPD I-KERNEL =========================================================================== This I-kernel contains instrument pointing data for the energetic particle detector (EPD) on board the Galileo Orbiter. The EPD instrument consists of a solid state detector telescope (LEMMS) and a foil type detector telescope (CMS). Both telescopes are mounted on a rotating platform which, in turn, is mounted on an electronics package. The LEMMS telescope has a 45 deg x 15 deg conical field of view emanating from opposite ends and the CMS telescope has a 27 deg x 45 deg conical field of view emanating from opposite ends. The platform rotates in cone in eight discrete steps. (These steps are refered to as sectors.) References -------------------------------------------------------- 1. ``Preliminary I-kernel Specification,'' (NAIF document number 177.0), by Ian Underwood, 1/19/90. 2. KERNEL ``Required Reading'' file. 3. ``Galileo Orbiter Flight Equipment: Configuration'' in GALILEO FUNCTIONAL REQUIREMENTS BOOK, JPL Document GLL-3-180C, 28 APR 1989. 4. ``EPD Specifications'', by Jim Willet, NAIF Document number 206.0 Implementation Notes -------------------------------------------------------- This file is used by the SPICE system as follows: programs that make use of the 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 ( 'GLL25001.TI' ) In order for a program or subroutine to extract data from the pool, the SPICELIB routine RTPOOL is used. See [2] for more details. Naming Conventions -------------------------------------------------------- All names referencing values in this I kernel start with the characters `INS' followed by the NAIF EPD instrument number ('-77' followed by the instrument subsystem reference number). This naming scheme is standard for all I-kernel files and was instituted to distinguish I-kernel data from other types of data that may also be loaded in the kernel pool. The remainder of the name is an underscore character, followed by the unique name of the data item. For example, the maximum acceptance angle for the Ja detector is specified by INS-77025_JA_MAX_ACCEP_ANGLE 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. DATA -------------------------------------------------------- The CMS has five detectors: 1 - Ja 2 - Ka 3 - Jb 4 - Kb 5 - Kt The LEMMS has eight detectors: 1 - A 2 - B 3 - C 4 - D 5 - E1 6 - E2 7 - F1 8 - F2 To find the direction of one of the above detectors at a known sector one of two alignment tables (TABLE_1 and TABLE_2) is used. The direction is returned from an alignment table in the form of a vector expressed relative to the spacecraft Xr, Yr, and Zr axes. On the CMS, the Ja & Ka and Jb & Kb detectors use TABLE_2 for alignment and the Kt detector uses TABLE_1 for alignment. On the LEMMS all but the C & D detectors use TABLE_1 for alignment. The data item INS-77025_DETECTOR_ALIGNMENT contains this information. If we let D be an array of the detectors listed in alphabetical order, then the I'th element in INS-77025_DETECTOR_ALIGNMENT tells us which alignment table should be used for the D(I) detector. See the table below. Alignment D - Detector names in Table alphabetical order ------- -------- INS-77025_DETECTOR_ALIGNMENT = 1 -- A 1 -- B 2 -- C 2 -- D 1 -- E1 1 -- E2 1 -- F1 1 -- F2 2 -- JA 2 -- JB 2 -- KA 2 -- KB 1 -- KT \begindata INS-77025_DETECTOR_ALIGNMENT = ( 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 2, 2, 1 ) \begintext Each of these detectors has an acceptance angle associated with it. The array INS-77025_ACCEPTANCE_ANGLE contains these acceptance angles. If the array D is still the names of the detectors listed in alphabetical order, then the I'th element in INS-77025_ACCEPTANCE_ANGLE is the acceptance angle of the D(I) detector. The angles are in units of degrees off axis. \begindata INS-77025_ACCEPTANCE_ANGLE = ( 15, 15, 45, 45, 15, 15, 15, 15, 11.5, 27, 11.5, 27, 18 ) \begintext The alignment tables each contain eight pointing vectors corresonding to the eight sectors. The vectors are expressed relative to the spacecraft +Xr, +Yr, and +Zr axes. INS-77025_EPD_TABLE1 and INS-77025_EPD_TABLE2 are the names of the two tables. The first three values in an alignment table are the Xr, Yr, and Zr components of the pointing vector for the first sector. The next three are the components for the second sector, and so on. X Y Z \begindata INS-77025_ALIGN_TABLE1 = ( -0.73, 0.00, -0.68, -0.03, 0.00, -1.00, 0.48, 0.00, -0.88, 0.86, 0.00, -0.51, 1.00, 0.00, 0.00, 0.86, 0.00, 0.51, 0.48, 0.00, 0.88, -0.03, 0.00, 1.00 ) INS-77025_ALIGN_TABLE2 = ( 0.73, 0.00, 0.68, 0.03, 0.00, 1.00, -0.48, 0.00, 0.88, -0.86, 0.00, 0.51, -1.00, 0.00, 0.00, -0.86, 0.00, -0.51, -0.48, 0.00, -0.88, 0.03, 0.00, -1.00 ) \begintext Date on which the above data was entered into this I-kernel. \begindata INS-77025_DATA_ENTRY_DATE = @09-NOV-1990 \begintext Version The version number is always positive and given in the form V.X. V and X are incremented by following these rules: -- V is incremented by 1 when there is a structural change to an I-kernel. A structural change to an instrument kernel would be adding or deleting data items or changing the number of values associated with an existing data item. A structural change would also be assigning different units to values or changing the name of a data item. -- X is incremented by 1 only if pre-existing values are changed. \begindata INS-77025_VERSION = 1.0