PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 2024-02-01 NOTE = "C-Kernel Information" END_OBJECT = TEXT END General information about SPICE C-kernels ========================================= In the SPICE system, pointing data for an instrument platform, or for a specific instrument, are stored as C-kernels (CK). The pointing of a platform or an instrument is often expressed in terms of a transformation matrix from some standard base reference frame to a instrument-fixed frame. In the past, the instrument was often a camera, and the transformation was thus dubbed the ``C-matrix''; hence the choice of C as the name for the pointing kernel. Three types of Cassini C-kernel files are present on this volume: Imaging Science Subsystem (ISS) image navigation data C-kernels, Attitude and Articulation Control Subsystem (AACS) reconstructed and predicted orientation data. The data contained in C-kernel files can be accessed and manipulated by a collection of subroutines that are part of the SPICELIB library, the major component of the NAIF Toolkit. These subroutines can be integrated into user application programs. Information about obtaining the SPICE Toolkit is located in the "software" subdirectory of the main directory of this dataset. To use C-kernels, a Spacecraft Clock Kernel (SCLK) is required. Also, for C-Kernels containing orientation of project-defined frames, a Frame Kernel file is required. Refer to the CK Required Reading (ck.req) document provided with the Toolkit or available from the NAIF Node of the PDS, to get more information on how to access C-kernel data. It is not unusual for CK files to be revised. The user is urged to be sure that CK data have not been superseded by searching the latest data releases for appropriate coverage. Cassini C-kernels contained on this volume ========================================== This directory contains the SPICE C-kernel files for the Cassini mission. All files are in IEEE big endian binary format and suitable for use on UNIX workstations and MACs. The following CK files are provided in this volume: -- Cassini Spacecraft Orientation CK Files, produced by the Attitude and Articulation Control Subsystem (regular reconstructed and predicted CKs, and final post-mission predicted CKs) and NAIF (continuous reconstructed CKs for cruise, and "gapfill" predicted CKs): [StartDate]_[EndDate][Type][V][_xxxxxxxx].bc where: [StartDate] File coverage start date (YYDOY); [EndDate] File coverage stop date (YYDOY); [Type] Type of the data stored in the file: "r" = reconstruction (called "ACTUAL" in the PDS label), "p" = predict; [V] File version. The first file generated for a specific time frame is version "a". Subsequent files containing revised information for the same time period are given the next higher version letter -- "b", "c", etc; Only two version letters have a special meaning for CKs created after the end of the mission: "c" designates the continuous reconstructed cruise CKs, and "y" designates the final versions of predicted CKs. [_xxxxxxxxx] Optional freeform text that can be included to provide the user additional clues about the contents of the file. Example 1: the file 03215_03220ra.bc is a binary C-kernel containing reconstructed data ("r") that covers a time period in 2003 from day of the year 215 to 220. It is the first version of the reconstruction file ("a"). Example 2: the file 03274_04001rc.bc is a binary C-kernel containing reconstructed data ("r") that covers a time period in 2003 from day of the year 274 to 365. It is the final continuous version for cruise phases ("c"). Example 3: the file 15049_15049ra_hf.bc is a binary C-kernel containing high-fidelity ("_hf") reconstructed data ("r") that covers a short time period during the day 049 of the year 2015. It is the first version of the reconstruction file ("a"). Example 4: the file 17191_17258pf_as_flown.bc is a binary C-kernel containing predicted data ("p") based on as-executed sequence ("_as_flown") that covers a time period in 2017 from day of the year 191 to 258. It is the sixth version of the file ("f"). Note: suffixes "_live" and "_fsiv" were also used to designate predicted CKs based on as-executed sequences, produced during operations. Example 5: the file 17191_17258py_as_flown.bc is a binary C-kernel containing predicted data ("p") based on as-executed sequence ("_as_flown") that covers a time period in 2017 from day of the year 191 to 258. It is the final post-mission version of the file ("y"). These predicted CKs supersede all earlier version predicted CKs for the corresponding periods. Note: only the "_as_flown" suffix was used to designate predicted CKs based on as-executed sequences, produced after the mission. Example 6: the file 16001_17001pa_gapfill_v14.bc is a binary C-kernel containing predicted data ("p") filling small gaps ("_gapfill") between operational predicted CKs during the year 2016. It is the 14th revision of the first version of this file ("a", "v14"). -- Cassini ISS C-Smithed C-kernel files, produced by the ISS team: [StartDate]_[EndDate]c[Version]_ISS.bc where: [StartDate] File coverage start date (YYDOY); [EndDate] File coverage stop date (YYDOY); [Version] File version (beginning with the letter 'a' and incrementing from there). For example, the file: 99213_99243ca_ISS.bc is a binary C-smithed C-kernel that covers the time period from 1999, day 213 to day 243 and it is the first version of this file. Note that complete time coverage for C-kernels is not guaranteed to be available for each release of data due to the processing schedule of AACS. -- Cassini CDA Instrument orientation C-kernel files, produced by the NAIF team using the instrument position data provided by the CDA team: cas_cda_[CreationDate].bc where: [CreationDate] File creation date (YYYYMMDD); For example, the file: cas_cda_20061027.bc is a binary CDA orientation C-kernel created on 2006-10-27. The CDA CK file with the latest creation date supersedes all previous CDA CK files. Note that because the CDA articulation angle tables used as input for creating these CKs frequently provide predicted data at the end of coverage, the CDA orientation during days or even months at the end of coverage of any given CDA CK may reflect reality. -- Cassini MIMI/LEMMS Instrument orientation C-kernel files, produced by the MIMI/LEMMS team at APL using the instrument position data from telemetry: cas_lemms_[YYDOY]_[yydoy]_v[N].bc where: [YYDOY] File coverage begin date [yydoy] File coverage end date [N] File version For example, the file: cas_lemms_05109_20001_v1.bc is a binary MIMI/LEMMS orientation C-kernel covering from 2005-04-19 to 2020-01-01, version 1. Note that the version 1 MIMI/LEMMS CKs covering from June 2000 to February 2005, added to the data set in the release 20 provided erroneous data for a significant part of their coverage, especially during the period from April 2001 to October 2003. The version 2 MIMI/LEMMS CKs covering the same time interval, added to the data set in the release 26 fully supersede the version 1 CKs. They fix most of the errors found in the version 1 CKs, except for a small set of time intervals when instrument pointing could not be reliably determined. Data for these intervals was removed from the version 2 MIMI/LEMMS CKs and saved for the record in a special CK named cas_lemms_00153_05059_bad_v2.bc -- Special Cassini MIMI/LEMMS C-kernel files providing orientation of a few Saturn frames defined in the the MIMI FK, produced by the MIMI/LEMMS team at APL: cas_skr_[FRAME]_[YYDOY]_[yydoy]_v[N].bc where: [FRAME] The frame specifier token. [YYDOY] File coverage begin date [yydoy] File coverage end date [N] File version For example, the file: cas_skr_slsm_south_04001_10192_v2.bc is a special binary C-kernel covering from 2004-01-01 to 2010-07-11, providing orientation of the CASSINI_SKR_SLSM_SOUTH frame defined in the MIMI FK. -- Cassini CAPS Instrument orientation C-kernel files, produced by NAIF/JPL using the CAPS articulation angle data from CAPS ACT products in the CAPS PDS data sets and the nominal relationship between the CAPs frames in the CASSINI FK: cas_caps_[YYDOY]_[yydoy]_v[N].bc where: [YYDOY] File coverage begin date [yydoy] File coverage end date [N] File version For example, the file: cas_caps_08001_08032_v2.bc is a binary CAPS orientation C-kernel covering from 2008-01-01 to 2008-02-01, version 2. Kernel File Details =================== The most detailed description of the data in a binary CK file is provided in metadata included inside the comment area of the file. This information can be viewed using the utility programs COMMNT and SPACIT included in the NAIF Toolkit. The Toolkit is available from the NAIF website. Comparisons between some AACS predicted and reconstructed C-kernels can be found in the ``extras/ckxtra/cknav/'' directory. Additional information about ISS C-kernels can be found in the ``extras/ckxtra/ckiss'' directory. Contact Information =================== Regarding Cassini project specific information provided in this data set and for general information about the SPICE system: Boris Semenov (818)-354-8136 Boris.Semenov@jpl.nasa.gov or Adrian W Tinio (818)-354-7511 Adrian.W.Tinio@jpl.nasa.gov address: Navigation and Ancillary Information Facility (NAIF) Jet Propulsion Laboratory MS 301-125L 4800 Oak Grove Drive Pasadena CA 91109 USA