KPL/IK ISS Instrument Kernel ============================================================================== This instrument kernel (I-kernel) contains references to the mounting alignment, internal and FOV geometry for the Cassini Imaging Science Subsystem (ISS) 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 ISS I-Kernel Version: \begindata TEXT_KERNEL_ID += 'CASSINI_ISS V0.9.0 23-JANUARY-2004 IK' \begintext Version 0.9 -- January 23, 2004 -- Josh Riley and Lee Elson -- Updated focal lengths using inflight calibration results. Version 0.8 -- April 23, 2001 -- Scott Turner -- Updated kernel to utilize new FOV ANGLES specification. Version 0.7 -- September 27, 2000 -- Scott Turner -- The value of IFOV for the NAC recorded in previous kernels as 60 should have been 6. The value associated with INS-82360_IFOV and the table in the documentation have been updated to reflect this correction. Version 0.6 -- August 15, 2000 -- Scott Turner -- Recalculated the FOV definitions to enhance precision. Version 0.5 -- June 7, 2000 -- Scott Turner -- Changed the INS[#]_FOV_CENTER_PIXEL keyword to reflect changes in the I-kernel SIS. Version 0.4 -- March 27, 2000 -- Scott Turner -- Included sample code in FORTRAN and C for computing the angular extents of the ISS fields of view. -- Added the TEXT_KERNEL_ID keyword. -- Minor cosmetic alterations to the structure of the kernel to improve readability. Version 0.3 -- March 17, 2000 -- Scott Turner -- This I-kernel reflects changes discussed at the SPICE team meeting on 3/16/2000. -- All of the INS[ID]_SEQ_[WORD] keywords were eliminated. -- INS[ID]_SEQ_FOV_CENTER is now keyed to INS[ID]_FOV_CENTER_PIXEL. Version 0.2 -- March 6, 2000 -- Scott Turner -- Fixed a few errors in the comment text describing the ISS and this kernel's intended usage. -- Removed 'NAC' and 'WAC' from keywords. These values were necessary when both the NAC and WAC shared a single instrument ID code. -- Added 'SEQ_' to the FOV keywords that are to be used by PDT and possibly other sequence tools. -- Added name to ID code mappings for 'CASSINI_ISS_NAC' and 'CASSINI_ISS_WAC' -- Added the keywords 'INS-82360_SEQ_PIXEL_SIZE', 'INS-82361_SEQ_PIXEL_SIZE', 'INS-82360_FOV_NAME', 'INS-82361_FOV_NAME', 'INS-82360_BORESIGHT_ID', 'INS-82361_BORESIGHT_ID', 'INS-82360_BORESIGHT_NAME', 'INS-82361_BORESIGHT_NAME' Version 0.1 -- October 8, 1999 -- Scott Turner -- Added an additional set of keywords that describe the FOVs of the instruments to maintain compatibility with previously discussed standards. These keywords may change or be eliminated when the kernel evolves. Placeholders for the NAC and WAC radiators were also placed into keywords conforming to this standard. -- Altered the NAC/WAC FOV definition parameters to conform with GETFOV's expectations. Added documentation describing the parameters. -- Changed NAC and WAC ID codes from -82010 and -82020 to -82360 and -82361 respectively. -- Altered reference No. 4 to include proper document title and project document number. -- Added a section for data to store instrument mode timing. The values present are just place holders until the actual ones are uncovered. Version 0.0 -- June 21, 1999 -- Scott Turner -- Initial Prototype Release for Review. References ---------------------------------------------------------- 1. ``Cassini Science Instruments and Investigations'', Revised Second Printing. Stephen J. Edberg. 2. Cassini Spacecraft Frames Definition Kernel. 3. JPL Cassini Project Web Page describing the instruments. 4. Cassini Document No. 699-416 Imaging Science Subsystem Calibration Report 5. Email from Jeff Boyer regarding necessary data for footprint calculations. 6. Email discussion with Vance Haemmerle regarding the location of the (0,0) pixel on the CCD and it's correlation to the NAC and WAC FOV definition. 7. Cassini/NAIF SPICE Workshop, November 8-9, 1999. 8. Email from Vance Haemmerle regarding an incorrect value recorded for the NAC IFOV parameter. 9. Memo from P. Thomas "Geometric calibration of the ISS NAC and WAC", December 18, 2002. Contact Information ---------------------------------------------------------- Direct questions, comments or concerns about the contents of this kernel to: Lee Elson, NAIF/JPL, (818)-354-4223, Lee.Elson@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 ID code for the ISS instruments. (NAC = 360, WAC = 361). The remainder of the name is an underscore character followed by the unique name of the data item. For example, the ISS NAC boresight direction in the ISS NAC optics frame (``CASSINI_ISS_NAC'' -- see [2]) is specified by: INS-82360_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. ISS description ---------------------------------------------------------- From [3]: ``IMAGING SCIENCE SUBSYSTEM (ISS) The Cassini orbiter imaging experiments will encompass a wide variety of targets (Saturn, the rings, Titan, the icy satellites, and star fields) and a wide range of observing distances for various scientific purposes. The science objectives include studying the atmospheres of Saturn and Titan, the rings of Saturn and their interactions with the planet's satellites, and the surface characteristics of the satellites, including Titan. Because of these multiple objectives, the Imaging Science Subsystem (ISS) has two separate camera designs. The first is a narrow-angle camera (NAC) design that will obtain high-resolution images of the target of interest. The second is a wide-angle camera (WAC) design that provides a different scale of image resolution and more complete coverage spatially. The spacecraft will carry one NAC and one WAC. The NAC is also used to obtain optical navigation images for the mission with the WAC acting as a functionally redundant backup unit for this purpose. The cameras are charge-coupled device (CCD) imagers. A CCD is essentially a large-scale integrated circuit (IC) that has a two-dimensional array of hundreds or thousands of charge-isolated wells, each representing a picture element or "pixel." Light falling on a well is absorbed by a photoconductive substrate, such as silicon, which releases a quantity of electrons proportional to the intensity of the light. The CCD detects and stores an accumulated electrical charge representing the light level on each well. These charges are subsequently read out for conversion to digital data. CCDs are much more sensitive to light of a wider spectrum than vidicon tube-type imagers, and they are less massive, require less energy, and interface more easily with digital circuitry. The Cassini imagers differ primarily in the design of the optics. The NAC has a focal length of 2000 mm, and the WAC , which uses optics inherited from the Voyager mission, has a focal length of 200 mm. The cameras each have a focal plane shutter of the same type as used on both Voyager and Galileo, and they have a two-wheel filter-changing mechanism derived from the Hubble Space Telescope Wide Field/Planetary Camera (WF/PC) design. The CCD detector is cooled to suppress dark current (residual current in the CCD beyond that released by incident light), which is dependent upon temperature. It is also shielded from ionizing radiation. The CCD detector design is a square array of 1024x1024 pixels, each pixel 12 micrometers on a side. The IC chip will use three-phase, front-side-illuminated architecture, with a coating of lumogen phosphor to provide ultraviolet response. The detector is passively cooled by a radiator to approximately 10 degrees C below its nominal operating temperature (approximately minus 90 degrees C), and then it is controlled to the operating temperature by a proportional control heater. To minimize radiator size and heater power, the detector/radiator combination is thermally isolated from the rest of the camera head assembly (CHA). The entire NAC is thermally isolated from the remote sensing pallet (RSP) on which it is mounted in order to minimize the effects of RSP thermal variations on NAC image quality. The WAC, being an inherited design with less stringent imaging requirements, is not thermally isolated. The electronics for each camera are identical. All ISS command and telemetry functions will be handled by the electronics, including receipt of commands from the Command and Data Subsystem, expansion of commands, and collection and transmission of imaging data and telemetry to the CDS. The ISS controls the amount of power it draws from the spacecraft during operations. To accomplish this, the profile of ISS command timing is structured to reduce the power the ISS requires for certain internal functions (e.g., shutter or filter wheel movement). When the filter is moving, the power from the optical heater (if present) in the active camera is turned off. When the movement is complete, the optical heater is turned on (if needed). In addition, simultaneous filter positioning within a single camera, either the WAC or NAC, is not permitted. During the cruise phase of the mission, the cameras will periodically be turned on for maintenance, calibration, and monitoring of instrument health and performance. Other than these specified times, the ISS will be off and replacement heaters will be on. In addition, decontamination/radiation heater 1 will be on throughout most of the cruise. Upon arrival at the Saturnian system, the cameras will be on most of the time. Spacecraft power limitations will be the controlling parameter determining whether the ISS will be turned off or put into a low-power state. During the Saturn tour, high-activity periods for Saturn and its rings will be clustered around periapsis (the point in the orbit closest to the planet); for the satellites, the high-activity periods will be when the spacecraft is closest to them. At these times, high-resolution images of all targets will be acquired through various camera filters, and the data will be stored in the spacecraft solid-state recorder (SSR). During lower activity periods (i.e., when the spacecraft is orbiting farther from the targets), long-term atmospheric and ring monitoring will take place, and ISS calibrations will be performed.'' ISS First Order Optical Parameters ---------------------------------------------------------- The first order optical parameters for the two cameras that constitute the ISS detectors: -- Narrow Angle Camera -- Wide Angle Camera as provided by [4 and 9] for the CL filter combinations compiled into the following table: ------------------------------ ----------- ----------- parameter NAC WAC ------------------------------ ----------- ----------- Effective Focal Length, mm 2003.44 200.77 Estimated Uncertainty, mm 0.03 0.01 Spectral Band, nm 200-1100 400-1000 F/number 10.5 3.44 ------------------------------ ----------- ----------- These values are given in the keywords below in the same units as the table above: Narrow Angle Camera (NAC): \begindata INS-82360_FOCAL_LENGTH = ( 2003.44 ) INS-82360_FL_UNCERTAINTY = ( 0.03 ) INS-82360_WAVELENGTH_RANGE = ( 200, 1100 ) INS-82360_F/NUMBER = ( 10.5 ) \begintext Wide Angle Camera (WAC): \begindata INS-82361_FOCAL_LENGTH = ( 200.77 ) INS-82361_FL_UNCERTAINTY = ( 0.01 ) INS-82361_WAVELENGTH_RANGE = ( 400, 1000 ) INS-82361_F/NUMBER = ( 3.44 ) \begintext ISS Field of View Parameters ---------------------------------------------------------- FOV Sizes (in degrees) Spacecraft Frame: Xsc ^ | | o-----> Ysc Zsc ^ Samples | Ycm (0,0) + + + > | + \_____________________________________________________ ___ + | | | + | Samples | | V | (0,0) + + + > | | Lines | + \_____________________________ ___ | | | + | | | | | | + | | | | | | V | | | | | | Lines | | | | | | | | | | | <--- | | x | 0.35 | 3.4 Xcm | | Zcm | | | | | | | | | | | | | | | | | | | | | | | |_____________________________| _|_ | | | NAC | | | |------------0.35-------------| | | | | | |_____________________________________________________| _|_ WAC |------------------------3.48-------------------------| Note that although the above diagram suggests that the NAC and WAC boresights are co-aligned, this is not the case. As [1] and [2] point out, the NAC and WAC are both mounted to the Remote Sensing Palette in different locations. From [6], the CCD samples and lines increase with decreasing X and Y in the NAC and WAC frames. Thus the (0,0) corners of the CCDs are as illustrated on the diagram above. The FOVs of the ISS detectors have the following angular sizes (from [4]): ------------ ---------------- ---------------- Detector Horizontal Vertical ------------ ---------------- ---------------- NAC 0.35 degrees 0.35 degrees WAC 3.48 degrees 3.48 degrees ------------ ---------------- ---------------- The CCD geometry parameters as presented in [1] and [4] are provided below: ------------------------------ ----------- ----------- parameter NAC WAC ------------------------------ ----------- ----------- Detector Array Size 1024x1024 1024x1024 Pixel Size, microns 12x12 12x12 FOV Angular Size, degrees 0.35x0.35 3.48x3.48 IFOV, microradian/pixel 6 60 ------------------------------ ----------- ----------- With the keywords and their values: Narrow Angle Camera (NAC): \begindata INS-82360_PIXEL_SAMPLES = ( 1024 ) INS-82360_PIXEL_LINES = ( 1024 ) INS-82360_PIXEL_SIZE = ( 12 ) INS-82360_CCD_CENTER = ( 512.5, 512.5 ) INS-82360_IFOV = ( 6 ) \begintext Wide Angle Camera (WAC): \begindata INS-82361_PIXEL_SAMPLES = ( 1024 ) INS-82361_PIXEL_LINES = ( 1024 ) INS-82361_PIXEL_SIZE = ( 12 ) INS-82361_CCD_CENTER = ( 512.5, 512.5 ) INS-82361_IFOV = ( 60 ) \begintext The keywords INS[ID]_FOV_FRAME, INS[ID]_FOV_SHAPE, INS[ID]_BORESIGHT, and FOV ANGLES specification keywords defined below are used to describe the instrument field of view. Since both the NAC and WAC have square fields of view, the INS[ID]_FOV_SHAPE keyword will always be 'RECTANGLE', and GETFOV will return the four vectors in the instrument frame that describe the edges of the FOV cone. Both the NAC and WAC boresights lie along the Z-axis. Narrow Angle Camera (NAC) FOV Definition Since the NAC's angular separation is 0.35 degrees, looking up the Y-axis in the CASSINI_ISS_NAC frame we have: (Note we are arbitrarily choosing vectors that terminate in the Z=1 plane.) ^ X | ins | | /| | / | | / | | / o | |/ 0.175 | o---------------> Y \ | Z ins \ | ins \ | \ | \| |-- 1.0 --| Plane Y = 0 Now from here we see that the X components of the boundary corners are: X Component = +/- 1.0 * tan ( 0.175 degrees ) = +/- 0.003054335689 Since the field of view is square this holds for the Y components as well. These FOV values as well as the values from the preceding table are given in the keywords below in the same units as listed above: Narrow Angle Camera (NAC): \begindata INS-82360_FOV_FRAME = 'CASSINI_ISS_NAC' INS-82360_FOV_SHAPE = 'RECTANGLE' INS-82360_BORESIGHT = ( 0.0000000000000000 0.0000000000000000 +1.0000000000000000 ) INS-82360_FOV_CLASS_SPEC = 'ANGLES' INS-82360_FOV_REF_VECTOR = ( +1.0000000000000000 0.0000000000000000 0.0000000000000000 ) INS-82360_FOV_REF_ANGLE = ( 0.175 ) INS-82360_FOV_CROSS_ANGLE = ( 0.175 ) INS-82360_FOV_ANGLE_UNITS = 'DEGREES' \begintext Wide Angle Camera (WAC) FOV Definition Since the WAC is also a square field of view, similar calculations as to those made for the NAC hold. The half angle of interest is 1.74 degrees as opposed to 0.175. Looking up the Y-axis in the CASSINI_ISS_WAC frame we have: (Note we are arbitrarily choosing vectors that terminate in the Z=1 plane.) ^ X | ins | | /| | / | | / | | / o | |/ 1.740 | o---------------> Y \ | Z ins \ | ins \ | \ | \| |-- 1.0 --| Plane Y = 0 Now from here we see that the X components of the boundary corners are: X Component = +/- 1.0 * tan ( 1.74 degrees ) = +/- 0.030378068382 Since the field of view is square this holds for the Y components as well. Again since the field of view is square this computation holds for the Y components as well. All of these values are collected in the FOV keywords defined below. Utilizing the ANGLES FOV specification: Wide Angle Camera (WAC): \begindata INS-82361_FOV_FRAME = 'CASSINI_ISS_WAC' INS-82361_FOV_SHAPE = 'RECTANGLE' INS-82361_BORESIGHT = ( 0.0000000000000000 0.0000000000000000 +1.0000000000000000 ) INS-82361_FOV_CLASS_SPEC = 'ANGLES' INS-82361_FOV_REF_VECTOR = ( +1.0000000000000000 0.0000000000000000 0.0000000000000000 ) INS-82361_FOV_REF_ANGLE = ( 1.74 ) INS-82361_FOV_CROSS_ANGLE = ( 1.74 ) INS-82361_FOV_ANGLE_UNITS = 'DEGREES' \begintext ISS Radiator FOV Definitions The FOV values for the ISS radiators are place holders until a time when real values are provided. Narrow Angle Camera Radiator (NAC_RAD): \begindata INS-82368_FOV_FRAME = 'CASSINI_ISS_NAC_RAD' INS-82368_FOV_SHAPE = 'CIRCLE' INS-82368_BORESIGHT = ( 0.0000000000000000 0.0000000000000000 +1.0000000000000000 ) INS-82368_FOV_CLASS_SPEC = 'ANGLES' INS-82368_FOV_REF_VECTOR = ( 0.0000000000000000 +1.0000000000000000 +0.0000000000000001 ) INS-82368_FOV_REF_ANGLE = ( 90.0 ) INS-82368_FOV_ANGLE_UNITS = 'DEGREES' \begintext Wide Angle Camera Radiator (WAC_RAD): \begindata INS-82369_FOV_FRAME = 'CASSINI_ISS_WAC_RAD' INS-82369_FOV_SHAPE = 'CIRCLE' INS-82369_BORESIGHT = ( 0.0000000000000000 0.0000000000000000 +1.0000000000000000 ) INS-82369_FOV_CLASS_SPEC = 'ANGLES' INS-82369_FOV_REF_VECTOR = ( 0.0000000000000000 +1.0000000000000000 +0.0000000000000001 ) INS-82369_FOV_REF_ANGLE = ( 90.0 ) INS-82369_FOV_ANGLE_UNITS = 'DEGREES' \begintext 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. The FOV_CENTER_PIXEL keyword is precisely the same as the CCD_CENTER defined in the CCD geometry keywords above. Narrow Angle Camera (NAC) \begindata INS-82360_FOV_CENTER_PIXEL = ( 511.5, 511.5 ) \begintext Wide Angle Camera (WAC) \begindata INS-82361_FOV_CENTER_PIXEL = ( 511.5, 511.5 ) \begintext Narrow Angle Camera Radiator (NAC_RAD) \begindata INS-82368_FOV_CENTER_PIXEL = ( 0, 0 ) INS-82368_PIXEL_SAMPLES = ( 1 ) INS-82368_PIXEL_LINES = ( 1 ) \begintext Wide Angle Camera Radiator (WAC_RAD) \begindata INS-82369_FOV_CENTER_PIXEL = ( 0, 0 ) INS-82369_PIXEL_SAMPLES = ( 1 ) INS-82369_PIXEL_LINES = ( 1 ) \begintext Instrument Mode Timing ---------------------------------------------------------- The following values were provided as samples in [5]. The 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.'' NAC Mode Timing The following values define the instrument modes and timing for the ISS NAC. \begindata INS-82360_MODE_NAME = 'NOMINAL' INS-82360_TRIGGER_OFFSET = '0:01:00.0' INS-82360_CYCLE_DURATION = '0:01:00.0' \begintext WAC Mode Timing The following values define the instrument modes and timing for the ISS WAC. \begindata INS-82361_MODE_NAME = 'NOMINAL' INS-82361_TRIGGER_OFFSET = '0:01:00.0' INS-82361_CYCLE_DURATION = '0:01:00.0' \begintext NAIF ID Code to Name Mapping ---------------------------------------------------------- The following keywords define names for the corresponding ID Codes. See [10] for details. \begindata NAIF_BODY_NAME += ( 'CASSINI_ISS_NAC' ) NAIF_BODY_CODE += ( -82360 ) NAIF_BODY_NAME += ( 'CASSINI_ISS_WAC' ) NAIF_BODY_CODE += ( -82361 ) NAIF_BODY_NAME += ( 'CASSINI_ISS_NAC_RAD' ) NAIF_BODY_CODE += ( -82368 ) NAIF_BODY_NAME += ( 'CASSINI_ISS_WAC_RAD' ) NAIF_BODY_CODE += ( -82369 ) \begintext Platform ID ---------------------------------------------------------- The ISS instrument is mounted on the Remote Sensing Palette, which is connected to the Cassini Spacecraft body. Therefore the value in the keywords below is -82000. \begindata INS-82360_PLATFORM_ID = ( -82000 ) INS-82361_PLATFORM_ID = ( -82000 ) INS-82368_PLATFORM_ID = ( -82000 ) INS-82369_PLATFORM_ID = ( -82000 ) \begintext