KPL/IK CDA Instrument Kernel ============================================================================== This instrument kernel (I-kernel) contains references to the mounting alignment, internal and FOV geometry for the Cassini Cosmic Dust Analyzer (CDA) 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 CDA I-Kernel Version: \begindata TEXT_KERNEL_ID += 'CASSINI_CDA 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 -- September 26, 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 CDA I-kernel Version 5.0 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 CDA detector. (790). The remainder of the name is an underscore character followed by the unique name of the data item. For example, the CDA boresight direction in the CDA frame (``CASSINI_CDA'' -- see [6] ) is specified by: INS-82790_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. CDA description ---------------------------------------------------------- From [3]: The Cosmic Dust Analyzer Subsystem (CDA) will provide direct observations of dust and ice particles in interplanetary space and in the Jupiter and Saturn systems. It will investigate the physical, chemical, and dynamical properties of these particles matter as functions of the distances to the Sun, to Jupiter, to Saturn, and to Saturn's satellites and rings. Finally, it will study the interaction of the particles with the Saturnian rings, satellites, and magnetosphere. The four major functional elements of the CDA are the dust analyzer, the main electronics, the articulation mechanism, and the high-rate detector assembly. For information on these components, see below. (CDA) The dust analyzer (DA) consists of the following components: four charge pick-up grids; a hemispherical target, an ion collector, an electron multiplier, and the sensor electronics. For information on these components, see below. (DA) The charge pick-up grids collect the initial impact particles. They are mounted at the entrance of the sensor. The hemispherical target is divided into two parts -- a ring-shaped impact ionization target and a chemical analyzer target in the middle of the ionization target. The chemical analyzer target has an acceleration grid mounted 3 mm in front of it. The ion collector has a grid that is negatively biased in order to collect the positively charged plasma ions produced at the impact ionization target. The electron multiplier is located in the center of the hemispherical ion collector target. It amplifies the signal produced by ions capable of penetrating the ion collector grid. These ions originate from plasma produced by particle impact either on the impact ionization target or the chemical analyzer target. The output signal from the multiplier differs depending upon the target from which impacts are being measured. The sensor electronics are contained in an electronics box attached to the DA sensor chassis. Among other components, this box contains charge-sensitive amplifiers (CSAs) that measure the signals from all of the grids in the DA. The CDA main electronics include amplifiers and transient recorders, a control and timing unit, a microprocessor unit, a bus interface unit, a power input circuit, a low-voltage converter, and a housekeeping system. All CSA and electron multiplier signals are separately amplified by logarithmic amplifiers and then digitized by an analog-to-digital converter. The data are stored on transient recorders. Only the recorder connected to the pick-up grids is operated continuously. All others are activated only by a signal detected at a target or the acceleration grid. The control and timing unit stores and decodes information received from the microprocessor and produces all timing and synchronization signals required for instrument operation. The microprocessor samples and collects the buffered measurement data, coordinates the subsystem measurement cycle, controls the instrument operating modes, processes the data according to a program loaded in its memory, and outputs data to the spacecraft upon request through the bus interface unit (BIU). The BIU is the interface circuit between the spacecraft and the microprocessor and is powered by the CDA instrument. The power input circuit is the interface with the spacecraft Power and Pyrotechnics Subsystem (PPS) and contains a filter circuit and a regulator to produce a d.c. voltage to feed the low-voltage converter. The low-voltage converter is a d.c./d.c. converter that provides different regulated low voltages for the electronics circuits and the supply voltage for the high-voltage converters. The converters are synchronized to the 100-kHz clock provided through the BIU from the Command and Data Subsystem (CDS). The CDA housekeeping system is a data system that multiplexes, digitizes, and stores information on the instrument current, the low voltages, the high voltages, and temperature measurements. The articulation mechanism (AM) allows the entire CDA instrument, including the high-rate detectors, the dust analyzer, the main electronics, and the articulation mechanism electronics, to be rotated or repositioned with respect to the spacecraft coordinate system. The high-rate detectors (HRDs) are two redundant independent sensors. The electronics for the sensors are contained in the HRD electronics box, and each sensor has its own electronics, independent of the other sensor. The HRD will be operated in two modes: "normal" mode and "calibrate." In the normal mode, the operational HRD continuously collects dust particle data. In the calibrate mode, a calibration cycle is initiated, which consists of a sequence of pulses sent to the HRD by the in-flight calibrator (IFC) to verify the stability of the electronics. CDA Field of View Parameters ---------------------------------------------------------- From [7] we have: Circular FOVs: ------------ ------------------- Detector Diameter ------------ ------------------- CDA 90.0 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 field of view. Since the CDA has a circular field of view the INS[ID]_FOV_SHAPE will be 'CIRCLE' The FOV boresight lies along the Z-axis in the 'CASSINI_CDA' frame. Since the CDA detector's FOV is circular and it's diameter is 90 degrees, looking down the X-axis in the CASSINI_CDA 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-82790_FOV_FRAME = 'CASSINI_CDA' INS-82790_FOV_SHAPE = 'CIRCLE' INS-82790_BORESIGHT = ( 0.0000000000000000 0.0000000000000000 +1.0000000000000000 ) INS-82790_FOV_CLASS_SPEC = 'ANGLES' INS-82790_FOV_REF_VECTOR = ( 0.0000000000000000 +1.0000000000000000 0.0000000000000000 ) INS-82790_FOV_REF_ANGLE = ( 45.0 ) INS-82790_FOV_ANGLE_UNITS = 'DEGREES' \begintext CDA 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. Cosmic Dust Analyzer (CDA): \begindata INS-82790_FOV_CENTER_PIXEL = ( 0, 0 ) INS-82790_PIXEL_SAMPLES = ( 1 ) INS-82790_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.'' \begindata INS-82790_MODE_NAME = 'NOMINAL' INS-82790_TRIGGER_OFFSET = '0:01:00.0' INS-82790_CYCLE_DURATION = '0:01:00.0' \begintext NAIF ID Code to Name Mapping ---------------------------------------------------------- The following keywords define the name for the corresponding ID Code. See [4] for details. \begindata NAIF_BODY_NAME += ( 'CASSINI_CDA' ) NAIF_BODY_CODE += ( -82790 ) \begintext Platform ID ---------------------------------------------------------- The CDA instrument is mounted on the Cassini Spacecraft body. Therefore the value in the keyword below is -82000. \begindata INS-82790_PLATFORM_ID = ( -82000 ) \begintext