KPL/IK INMS Instrument Kernel ============================================================================== This instrument kernel (I-kernel) contains references to the mounting alignment, internal and FOV geometry for the Cassini Ion and Neutral Mass Spectrometer (INMS) 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 INMS I-Kernel Version: \begindata TEXT_KERNEL_ID += 'CASSINI_INMS V0.2.0 23-APRIL-2001 IK' \begintext Version 0.2 -- April 23, 2001 -- Scott Turner -- Updated kernel to utilize new FOV ANGLES specification. Version 0.1 -- November 16, 2000 -- Scott Turner -- Changed the CASSINI_INMS_OPEN FOV defintion to reflect the correct size. Version 0.0 -- September 27, 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 INMS I-kernel Version 5.0 8. Email from Deborah Bass regarding incorrect CASSINI_INMS_OPEN FOV size. 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 INMS detectors. (OPEN = 740, CLOSED = 741). The remainder of the name is an underscore character followed by the unique name of the data item. For example, the INMS_OPEN boresight direction in the INMS frame (``CASSINI_INMS'' -- see [6] ) is specified by: INS-82740_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. INMS description ---------------------------------------------------------- From [3]: The Ion and Neutral Mass Spectrometer Subsystem (INMS) will be used to study the neutral gases and positive ions in the atmospheres of Saturn and Titan and gases in the vicinities of the Saturnian rings and the icy satellites. It will also study the magnetosphere of Saturn. The major functional components of the INMS Subsystem are an open ion source, a closed ion source, a quadrupole deflector and lens system, a quadrupole mass analyzer, and a dual detector system. For information on these components, see below. (INMS Links) The open ion source produces ions by ionizing neutral gases. It includes an ion trap/deflector that forms trapped ions into a beam. This minimizes interaction effects between the gas environment and the open source surface as the source directly samples the gaseous species. The closed ion source also produces ions by ionizing neutral gases. It uses ram density enhancement to provide measurements of higher accuracy and sensitivity for the more inert atomic and molecular species than provided by the open ion source. This is achieved by maintaining a high input flux to an enclosed antechamber and then limiting the gas conductance or output from the antechamber by the use of an orifice. Ions are directed to the mass analyzer from the selected ion source by changing the potentials on a 90-degree quadrupole deflector. This electrostatic device allows both sources of ions to be sequentially switched into a common exit lens system. The quadrupole mass analyzer consists of four precision ground hyperbolic rods mounted in a rigid mechanical assembly. The transmitted mass, the resolution, and the ion transmission are controlled by variations in RF and d.c. electric fields between adjacent rod pairs, while opposite rod pairs are kept at the same potential. The ion dual detector system amplifies and detects the input from the mass analyzer by the use of two continuous dynode multipliers. INMS Field of View Parameters ---------------------------------------------------------- The field of view parameters for the two detectors that constitute INMS are: -- Open (OPEN) -- Closed (CLOSED) Circular FOVs: ------------ ------------------- Detector Diameter ------------ ------------------- OPEN 8.0 degrees CLOSED 180.0 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 INMS has only circular fields of view the INS[ID]_FOV_SHAPE will always be 'CIRCLE', and GETFOV will always return a single boundary corner vector that lies along the edge of the circular cones. The FOV boresight lies along the Z-axis in the 'CASSINI_INMS' frame for both detectors. Open (OPEN) FOV Definition Since the INMS_OPEN detector's FOV is circular and it's diameter is 8.0 degrees, looking down the X-axis in the CASSINI_INMS frame, we have: (Note we are arbitrarily choosing a vector that terminates in the Z=1 plane.) ^ Y | ins | | /| | / | | / | | / o | |/ 4.0 | 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 ( 4.0 degrees ) = 0.069926812 Utilizing the ANGLES FOV specification: \begindata INS-82740_FOV_FRAME = 'CASSINI_INMS' INS-82740_FOV_SHAPE = 'CIRCLE' INS-82740_BORESIGHT = ( 0.0000000000000000 0.0000000000000000 +1.0000000000000000 ) INS-82740_FOV_CLASS_SPEC = 'ANGLES' INS-82740_FOV_REF_VECTOR = ( 0.0000000000000000 +1.0000000000000000 0.0000000000000000 ) INS-82740_FOV_REF_ANGLE = ( 4.0 ) INS-82740_FOV_ANGLE_UNITS = 'DEGREES' \begintext Closed (CLOSED) FOV Definition Since the INMS_CLOSED detector's FOV is also circular and it's diameter is 180.0 degrees. Looking down the X-axis in the CASSINI_INMS frame, we have: (Note since the FOV is 180 degrees in diameter we have the whole Z>=0 halfplane in the FOV.) ^ Y | ins ^ | | | o | 90.0 | x---------------> X Z ins ins |-- 1.0 --| Plane X = 0 Utilizing the ANGLES FOV specification: Boundary Corner Vector = ( 0, 1, 0 ) \begindata INS-82741_FOV_FRAME = 'CASSINI_INMS' INS-82741_FOV_SHAPE = 'CIRCLE' INS-82741_BORESIGHT = ( 0.0000000000000000 0.0000000000000000 +1.0000000000000000 ) INS-82741_FOV_CLASS_SPEC = 'ANGLES' INS-82741_FOV_REF_VECTOR = ( 0.0000000000000000 +1.0000000000000000 +0.0000000000000000 ) INS-82741_FOV_REF_ANGLE = ( 90.0 ) INS-82741_FOV_ANGLE_UNITS = 'DEGREES' \begintext INMS 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. Ion and Neutral Mass Spectrometer Open (INMS_OPEN): \begindata INS-82740_FOV_CENTER_PIXEL = ( 0, 0 ) INS-82740_PIXEL_SAMPLES = ( 1 ) INS-82740_PIXEL_LINES = ( 1 ) \begintext Ion and Neutral Mass Spectrometer Closed (INMS_CLOSED): \begindata INS-82741_FOV_CENTER_PIXEL = ( 0, 0 ) INS-82741_PIXEL_SAMPLES = ( 1 ) INS-82741_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.'' Open \begindata INS-82740_MODE_NAME = 'MASS_RANGE' INS-82740_TRIGGER_OFFSET = '0:01:00.0' INS-82740_CYCLE_DURATION = '0:01:00.0' \begintext Closed \begindata INS-82741_MODE_NAME = 'MASS_RANGE' INS-82741_TRIGGER_OFFSET = '0:01:00.0' INS-82741_CYCLE_DURATION = '0:01:00.0' \begintext NAIF ID Code to Name Mapping ---------------------------------------------------------- \begindata NAIF_BODY_NAME += ( 'CASSINI_INMS_OPEN' ) NAIF_BODY_CODE += ( -82740 ) NAIF_BODY_NAME += ( 'CASSINI_INMS_CLOSED' ) NAIF_BODY_CODE += ( -82741 ) \begintext Platform ID ---------------------------------------------------------- The INMS instrument is mounted on the Fields and Particles Palette, which is connected to the Cassini Spacecraft body. Therefore the values stored in the keywords below are -82000. \begindata INS-82740_PLATFORM_ID = ( -82000 ) INS-82741_PLATFORM_ID = ( -82000 ) \begintext