PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 2011-09-09 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. 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. Deep Impact C-kernels Contained on This Volume ============================================== This directory contains the SPICE C-kernel files for the Deep Impact 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 directory (only the leading portion of the file name is shown; the extension of all CK file names is ".bc"): dif_sc_050112_050809 Deep Impact Flyby (DIF) spacecraft orientation CK file based on the low rate real-time attitude telemetry and covering the whole primary mission. dif_sc_050112_050809_v2 Deep Impact Flyby (DIF) spacecraft orientation CK file based on the low rate real-time attitude telemetry and covering the whole primary mission, with corrected internal time tags. dif_sc_050225_highrate DIF spacecraft orientation CKs based dif_sc_050704_highrate on the high-rate recorded attitude telemetry covering two short windows when such telemetry was produced -- first at the beginning of the mission and second for about one hour around the closest encounter. dif_sc_050704_highrate_v2 DIF spacecraft orientation CK based on the high-rate recorded attitude telemetry covering about one hour around the closest encounter, with corrected internal time tags. dif_hga_050117_050801_vch DIF High Gain Antenna (HGA) orientation dif_hga_050118_050801_bch CK files produced from channelized telemetry, each covering the whole primary mission. The "vch" file is based on the "measured" gimbal angles while the "bch" file is based on the commanded channels. dii_sc_050112_050703 Deep Impact Impactor (DII) spacecraft dii_sc_050703_050704 orientation CK files. The first of the two files provides coverage for the whole period when DII was attached to DIF; attitude is this file is provided as a fixed offset of DII frame relative to the DIF frame derived from the in-flight calibration data. The second file provides DII orientation from separation until the impact; this orientation is based on DII attitude telemetry data. These CK files should be loaded into a user application in the following order to guarantee that, when available, the most accurate attitude data is returned to calling application ahead of the less accurate data: dif_hga_050118_050801_bch.bc dif_hga_050117_050801_vch.bc dif_sc_050112_050809_v2.bc dif_sc_050225_highrate.bc dif_sc_050704_highrate_v2.bc dii_sc_050112_050703.bc dii_sc_050703_050704.bc Deep Impact CK File Naming Scheme ================================= The Deep Impact CK provided on this volume are named according to the following scheme: sc_struct_YYMMDD[_yymmdd][_ident][_vX] where: sc is the name of the spacecraft: "dif" or "dii"; struct is the name of the spacecraft structure: "sc" for spacecraft itself; "hga" for the High Gain Antenna; YYMMDD is the file coverage start date; yymmdd is the file coverage stop date (optional; provided only if the file covers more than one day); ident is a token further identifying the data in the file (optional). Examples: "highrate" for high-rate data, "bch" for "B"-channel based attitude, etc. vX is the file version number (optional; if omitted, the file version is "0"). The file with the highest version number supersedes all files with the same name but earlier version numbers. 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. Contact Information =================== Regarding Deep Impact 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 Chuck Acton (818)-354-3869 Chuck.Acton@jpl.nasa.gov address: Navigation and Ancillary Information Facility (NAIF) Jet Propulsion Laboratory MS 301-125L 4800 Oak Grove Drive Pasadena CA 91109 USA