PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 2011-06-23 NOTE = "SCL-Kernel Information" END_OBJECT = TEXT END General information about SPICE SCL-kernels =========================================== In the SPICE system, the Spacecraft Clock Kernel (SCLK) contains information required to perform a mapping between Ephemeris time (ET) and spacecraft on-board time (SCLK). The spacecraft clock coefficient information contained in a SCLK file can be manipulated by a collection 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. Refer to the SCLK Required Reading (sclk.req) document provided with the Toolkit or available from the NAIF Node of the PDS, to get more information on how to convert between ET and spacecraft clock times. EPOXI SCL-kernels Contained in This Data Set ============================================ This data set contains the following Deep Impact Flyby (DIF) SCLK files (only the leading portion of the file name is shown; the extension of all file names is ".tsc"): dif_sclkscet_00035 "SCU A" DIF SCLK kernel file. This SCLK kernel provides correlation data for the primary (SCU A) DIF on-board clock. It was used in December 2008 by SDC/Cornell to generate products included in the EPOCh data sets archived in the PDS. It is included in the archive only for the record. dif_sclkscet_00036 "SCU A" DIF SCLK kernel file. This SCLK kernel provides correlation data for the primary (SCU A) DIF on-board clock. It provides the same data as as "dif_sclkscet_00035.tsc" for times before Jun 6, 2008 and updated, better data (differing by up to 4 seconds) for the times after Jun 6, 2008. dif_sclkscet_00037 "SCU A" DIF SCLK kernel file. This SCLK kernel provides correlation data for the primary (SCU A) DIF on-board clock. It provides the same data as as "dif_sclkscet_00036.tsc" for times before February 4, 2009. dif_sclkscet_00084 "SCU A" DIF SCLK kernel file. This SCLK kernel provides correlation data for the primary (SCU A) DIF on-board clock. This was the latest SCLK version used in operations at the end of the DIXI part of the mission. It is included in the archive only for the record. dif_sclkscet_00084_science "improved" DIF SCLK kernel file. This SCLK kernel provides data for the primary (SCU A) DIF on-board clock based on the latest ``official'' version used in operations (00084). This SCLK provides an improved correlation (as compared to the official SCLK) and was used for post Hartley 2 encounter data processing. dif_sclkscet_00014_scu_b "SCU B" DIF SCLK kernel files. These dif_sclkscet_00020_scu_b SCLK kernels provide correlation data for the secondary (SCU B) DIF on-board clock. The latest of these files includes the latest correlation version available at the end of the mission. Note that only one of DIF SCLK files must be loaded into a user application at any given time because all DIF SCLK kernels provide data for the same clock ID, -140. Since most applications will involve converting tags from the "SCU A" clock and the most accurate correlation is desired, the dif_sclkscet_00084_science.tsc file should be used. Note that the clock format defined by all archived SCLK kernels (seconds with fractional seconds given as a count of 1/256 second ticks) does not match the format of on-board time tags in mission telemetry (seconds with fractional seconds given as top 8 or 16 or full 20 bits of a count of micro-seconds). For details on this discrepancy and the algorithm to fix it see ``sclk140.txt'' provided in Deep Impact and EPOXI documentation set (DI-C-HRII/HRIV/MRI/ITS-6-DOC-SET-V3.0). EPOXI SCLK File Naming Scheme =================================== The EPOXI SCLKs provided in this data set are named according to the following scheme: dif_sclkscet_VVVVV[_ident].tsc where: sclkscet is the literal script carried over from the source SCLKvSCET file name; VVVVV is the file version number; ident is a token further identifying the data in the file (optional). Examples: "scu_b" for SCU B clock, etc. Kernel File Details =================== The most detailed description of the data in an SCLK file is provided in metadata included inside the descriptive text areas within the file. This information can be viewed using any text editor. Contact Information =================== Regarding EPOXI project specific information provided in this data set and for general information about 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