KPL/IK MAG Instrument Kernel ============================================================================== This instrument kernel (I-kernel) contains references to the mounting alignment, internal and FOV geometry for the Cassini Magnetometer (MAG) instruments. Version and Date ---------------------------------------------------------- The TEXT_KERNEL_ID stores version information of loaded project text kernels. Each entry associated with the keyword is a string that consists of four parts: the kernel name, version, entry date, and type. For example, the ISS I-kernel might have an entry as follows: TEXT_KERNEL_ID += 'CASSINI_ISS V0.0.0 29-SEPTEMBER-1999 IK' | | | | | | | | KERNEL NAME <-------+ | | | | | V VERSION <-------+ | KERNEL TYPE | V ENTRY DATE MAG I-Kernel Version: \begindata TEXT_KERNEL_ID += 'CASSINI_MAG V0.1.0 23-APRIL-2001 IK' \begintext Version 0.1 -- April 23, 2001 -- Scott Turner -- Updated kernel to utilize new FOV ANGLES specification. Version 0.0 -- October 3, 2000 -- Scott Turner -- Initial Prototype Release for Review References ---------------------------------------------------------- 1. ``Cassini Science Instruments and Investigations'', Revised Second Printing. Stephen J. Edberg. 2. ``Kernel Pool Required Reading'' 3. JPL Cassini Project Web Page describing the instruments. 4. Cassini/NAIF SPICE Workship, November 8-9, 1999. 5. Email from Jeff Boyer regarding necessary data for footprint calculations. 6. Cassini Spacecraft Frames Definition Kernel 7. CASPER MAG I-kernel Version 6.0 Contact Information ---------------------------------------------------------- Direct questions, comments or concerns about the contents of this kernel to: Scott Turner, NAIF/JPL, (818)-345-3157, sturner@spice.jpl.nasa.gov Implementation Notes ---------------------------------------------------------- This file is used by the SPICE system as follows: programs that make use of this instrument 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 FURNSH and CSPICE routine furnsh_c load SPICE kernels as shown below: FORTRAN (SPICELIB) CALL FURNSH ( 'kernel_name' ) C (CSPICE) furnsh_c ( "kernel_name" ) In order for a program or subroutine to extract data from the pool, the SPICELIB routines GDPOOL and GIPOOL are used. See [2] for details. This file was created and may 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 Cassini spacecraft ID number (-82) followed by a NAIF three digit code for the MAG detectors. (45PX = 350, 45MX = 351, 60PX = 352, 60MX = 353 ). The remainder of the name is an underscore character followed by the unique name of the data item. For example, the MAG_45PX boresight direction in the MAG_PLUS frame (``CASSINI_MAG_PLUS'' -- see [6] ) is specified by: INS-82350_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. MAG description ---------------------------------------------------------- From [3]: Magnetometers are direct-sensing instruments that detect and measure the strength of magnetic fields in the vicinity of the spacecraft. The Cassini Dual-Technique Magnetometer (MAG) measures magnetic fields during the Titan and Saturn encounters. The MAG consists of a vector/scalar helium magnetometer sensor, a fluxgate magnetometer sensor, a data processing unit, three power supplies, plus operating software and electronics associated with the sensors. The vector/scalar helium magnetometer (V/SHM) sensor is used to make both vector (magnitude and direction) and scalar (magnitude only) measurements of magnetic fields. The V/SHM and its electronics are being supplied by JPL. The fluxgate magnetometer (FGM) sensor is used to make vector field measurements. This sensor and its electronics are being provided by the Imperial College of London. The instrument data processing unit (DPU) is the responsibility of the Technical University of Braunschweig. The DPU interfaces with the spacecraft Command and Data Subsystem through the JPL-designed bus interface unit (BIU). All commands, data, and processor program changes are received or transmitted through the BIU. The MAG components are powered by three power supplies plus the 30-volt spacecraft bus. Power supply 0 powers the BIU and the DPU. Power supplies 1 and 2 are redundant and power the V/SHM electronics. The FGM electronics are powered by the spacecraft bus. Since magnetometers are sensitive to electric currents and ferrous components on the spacecraft, they are generally placed on an extended boom, as far from the spacecraft as possible. In this case, the FGM sensor is located midway out on the Cassini magnetometer boom, and the V/SHM sensor is located at the end of the boom. The boom itself, composed of thin, nonmetallic rods, will be collapsed very compactly during launch and deployed only after the spacecraft has separated from the launch vehicle. MAG Field of View Parameters ---------------------------------------------------------- The field of view parameters for the four detectors that constitute MAG are: -- 45 Degree -- Plus X (45PX) -- 45 Degree -- Minus X (45MX) -- 60 Degree -- Plus X (60PX) -- 60 Degree -- Minus X (60MX) Circular FOVs: ------------ ------------------- Detector Diameter ------------ ------------------- 45PX 90.0 degrees 45MX 90.0 degrees 60PX 120.0 degrees 60MX 120.0 degrees ------------ ------------------- The keywords INS[ID]_FOV_FRAME, INS[ID]_FOV_SHAPE, INS[ID]_BORESIGHT, and the FOV ANGLES specification keywords defined below are used to describe the instrument fields of view. Since the MAG detectors only have circular fields of view the INS[ID]_FOV_SHAPE will always be 'CIRCLE', and GETFOV will return a single boundary vector that lies along the edge of the circular cones. The FOV boresight vectors lie along the Z-axis in the 'CASSINI_MAG_PLUS' or 'CASSINI_MAG_MINUS' frames depending on the direction the detector is pointed. 45 Degree -- Plus X (45PX) FOV Definition Since the MAG_45PX detector's FOV is circular and it's diameter is 90.0 degrees, looking down the X-axis in the CASSINI_MAG_PLUS frame, we have: (Note we are arbitrarily choosing a vector that terminates in the Z=1 plane.) ^ Y | ins | | /| | / | | / | | / o | |/ 45.0 | x---------------> X \ | Z ins \ | ins \ | \ | \| |-- 1.0 --| Plane X = 0 Now from here we see that the Y component of one 'boundary corner' vector is: Y Component = 1.0 * tan ( 45.0 degrees ) = 1.0 Utilizing the ANGLES FOV specification: \begindata INS-82350_FOV_FRAME = 'CASSINI_MAG_PLUS' INS-82350_FOV_SHAPE = 'CIRCLE' INS-82350_BORESIGHT = ( 0.0000000000000000 0.0000000000000000 +1.0000000000000000 ) INS-82350_FOV_CLASS_SPEC = 'ANGLES' INS-82350_FOV_REF_VECTOR = ( 0.0000000000000000 +1.0000000000000000 0.0000000000000000 ) INS-82350_FOV_REF_ANGLE = ( 45.0 ) INS-82350_FOV_ANGLE_UNITS = 'DEGREES' \begintext 45 Degree -- Minus X (45MX) FOV Definition Since the MAG_45MX detector's FOV is circular and it's diameter is 90.0 degrees, looking down the X-axis in the CASSINI_MAG_MINUS frame, we have: (Note we are arbitrarily choosing a vector that terminates in the Z=1 plane.) ^ Y | ins | | /| | / | | / | | / o | |/ 45.0 | x---------------> X \ | Z ins \ | ins \ | \ | \| |-- 1.0 --| Plane X = 0 Now from here we see that the Y component of one 'boundary corner' vector is: Y Component = 1.0 * tan ( 45.0 degrees ) = 1.0 Again, utilizing the ANGLES FOV specification: \begindata INS-82351_FOV_FRAME = 'CASSINI_MAG_MINUS' INS-82351_FOV_SHAPE = 'CIRCLE' INS-82351_BORESIGHT = ( 0.0000000000000000 0.0000000000000000 +1.0000000000000000 ) INS-82351_FOV_CLASS_SPEC = 'ANGLES' INS-82351_FOV_REF_VECTOR = ( 0.0000000000000000 +1.0000000000000000 0.0000000000000000 ) INS-82351_FOV_REF_ANGLE = ( 45.0 ) INS-82351_FOV_ANGLE_UNITS = 'DEGREES' \begintext 60 Degree -- Plus X (60PX) FOV Definition Since the MAG_60PX detector's FOV is circular and it's diameter is 90.0 degrees, looking down the X-axis in the CASSINI_MAG_PLUS frame, we have: (Note we are arbitrarily choosing a vector that terminates in the Z=1 plane.) ^ Y | ins | | /| | / | | / | | / o | |/ 60.0 | x---------------> X \ | Z ins \ | ins \ | \ | \| |-- 1.0 --| Plane X = 0 Now from here we see that the Y component of one 'boundary corner' vector is: Y Component = 1.0 * tan ( 60.0 degrees ) = 1.732050808 Utilizing the ANGLES FOV specification: \begindata INS-82352_FOV_FRAME = 'CASSINI_MAG_PLUS' INS-82352_FOV_SHAPE = 'CIRCLE' INS-82352_BORESIGHT = ( 0.0000000000000000 0.0000000000000000 +1.0000000000000000 ) INS-82352_FOV_CLASS_SPEC = 'ANGLES' INS-82352_FOV_REF_VECTOR = ( 0.0000000000000000 +1.0000000000000000 0.0000000000000000 ) INS-82352_FOV_REF_ANGLE = ( 60.0 ) INS-82352_FOV_ANGLE_UNITS = 'DEGREES' \begintext 60 Degree -- Minus X (60MX) FOV Definition Since the MAG_45MX detector's FOV is circular and it's diameter is 90.0 degrees, looking down the X-axis in the CASSINI_MAG_MINUS frame, we have: (Note we are arbitrarily choosing a vector that terminates in the Z=1 plane.) ^ Y | ins | | /| | / | | / | | / o | |/ 60.0 | x---------------> X \ | Z ins \ | ins \ | \ | \| |-- 1.0 --| Plane X = 0 Now from here we see that the Y component of one 'boundary corner' vector is: Y Component = 1.0 * tan ( 60.0 degrees ) = 1.732050808 Again, utilizing the ANGLES FOV specification: \begindata INS-82353_FOV_FRAME = 'CASSINI_MAG_MINUS' INS-82353_FOV_SHAPE = 'CIRCLE' INS-82353_BORESIGHT = ( 0.0000000000000000 0.0000000000000000 +1.0000000000000000 ) INS-82353_FOV_CLASS_SPEC = 'ANGLES' INS-82353_FOV_REF_VECTOR = ( 0.0000000000000000 +1.0000000000000000 0.0000000000000000 ) INS-82353_FOV_REF_ANGLE = ( 60.0 ) INS-82353_FOV_ANGLE_UNITS = 'DEGREES' \begintext MAG Pixel Parameters: ---------------------------------------------------------- These parameters describe the pixel structure associated with the instruments and their fields of views. In some cases this is a generalization of the notion of pixel, in that instead of representing pixels on a CCD they may represent a collection of individual detectors. 45 Degree -- Plus X (45PX): \begindata INS-82350_FOV_CENTER_PIXEL = ( 0, 0 ) INS-82350_PIXEL_SAMPLES = ( 1 ) INS-82350_PIXEL_LINES = ( 1 ) \begintext 45 Degree -- Minus X (45MX): \begindata INS-82351_FOV_CENTER_PIXEL = ( 0, 0 ) INS-82351_PIXEL_SAMPLES = ( 1 ) INS-82351_PIXEL_LINES = ( 1 ) \begintext 60 Degree -- Plus X (60PX): \begindata INS-82352_FOV_CENTER_PIXEL = ( 0, 0 ) INS-82352_PIXEL_SAMPLES = ( 1 ) INS-82352_PIXEL_LINES = ( 1 ) \begintext 60 Degree -- Minus X (60MX): \begindata INS-82353_FOV_CENTER_PIXEL = ( 0, 0 ) INS-82353_PIXEL_SAMPLES = ( 1 ) INS-82353_PIXEL_LINES = ( 1 ) \begintext Instrument Mode Timing ---------------------------------------------------------- The following values were provided as samples in [5]. These values are defined in [5] as follows: ``The initial values for the following keywords are given per instrument number: INS[instrument number]_[instrument acronym]_MODE_NAME INS[instrument number]_[instrument acronym]_TRIGGER_OFFSET INS[instrument number]_[instrument acronym]_CYCLE_DURATION INS..._MODE_NAME contains the name of the instrument mode for the INS..._TRIGGER_OFFSET and INS..._CYCLE_DURATION keywords. INS..._TRIGGER_OFFSET specifies the reference time of the first instrument frame (to be calculated for a footprint) relative to the time of transacting the corresponding TRIGGER command. The units are SFOC duration. INS..._CYCLE_DURATION specifies the duration between successive instrument frames (from the first one) for the INS..._MODE_NAME.'' 45 Degree -- Plus X (45PX) \begindata INS-82350_MODE_NAME = 'NOMINAL' INS-82350_TRIGGER_OFFSET = '0:01:00.0' INS-82350_CYCLE_DURATION = '0:01:00.0' \begintext 45 Degree -- Minus X (45MX) \begindata INS-82351_MODE_NAME = 'NOMINAL' INS-82351_TRIGGER_OFFSET = '0:01:00.0' INS-82351_CYCLE_DURATION = '0:01:00.0' \begintext 60 Degree -- Plus X (60PX) \begindata INS-82352_MODE_NAME = 'NOMINAL' INS-82352_TRIGGER_OFFSET = '0:01:00.0' INS-82352_CYCLE_DURATION = '0:01:00.0' \begintext 60 Degree -- Minus X (60MX) \begindata INS-82353_MODE_NAME = 'NOMINAL' INS-82353_TRIGGER_OFFSET = '0:01:00.0' INS-82353_CYCLE_DURATION = '0:01:00.0' \begintext NAIF ID Code to Name Mapping ---------------------------------------------------------- \begindata NAIF_BODY_NAME += ( 'CASSINI_MAG_45PX' ) NAIF_BODY_CODE += ( -82350 ) NAIF_BODY_NAME += ( 'CASSINI_MAG_45MX' ) NAIF_BODY_CODE += ( -82351 ) NAIF_BODY_NAME += ( 'CASSINI_MAG_60PX' ) NAIF_BODY_CODE += ( -82352 ) NAIF_BODY_NAME += ( 'CASSINI_MAG_60MX' ) NAIF_BODY_CODE += ( -82353 ) \begintext Platform ID ---------------------------------------------------------- The MAG instrument is mounted on the Magentometer Boom, which is connected to the Cassini Spacecraft body. Therefore the values stored in the keywords below are -82000 \begindata INS-82350_PLATFORM_ID = ( -82000 ) INS-82351_PLATFORM_ID = ( -82000 ) INS-82352_PLATFORM_ID = ( -82000 ) INS-82353_PLATFORM_ID = ( -82000 ) \begintext