PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT NOTE = "Comments on the EPOXI SPICE Archive" PUBLICATION_DATE = 2011-06-23 END_OBJECT = TEXT END COMMENTS ON THE EPOXI SPICE DATA ARCHIVE ============================================== This document contains comments and errata concerning the EPOXI SPICE Data Archive. 1. Text Kernel File Format -------------------------- All SPICE text kernel files (LSK, PCK, SCLK, IK, FK) provided on these volumes have lines terminated by only (UNIX convention.) This is dictated by NAIF's archiving approach to include a consistent set of UNIX binary (IEEE architecture) and text ( only for end of line marker) kernels on the archive volumes. However, the format of the text kernels is specified in their associated labels as ASCII (INTERCHANGE_FORMAT = ASCII.) This is a violation of the PDS standard stating that lines in ASCII files must be delimited by the combination of . This line termination treatment is standard practice for SPICE volumes in the PDS. 2. Use of SPACECRAFT_NAME in the Labels --------------------------------------- PDS labels for SPICE kernels provided in this data set contain the deprecated keyword SPACECRAFT_NAME instead of the keyword INSTRUMENT_HOST_NAME. This is standard practice for SPICE volumes in the PDS and is dictated by NAIF's archiving approach to make SPICE archives for more recent missions consistent with SPICE archives for older missions, for which use of SPACECRAFT_NAME was legitimate. 3. Values of INSTRUMENT_NAME in the Labels ------------------------------------------ PDS labels for SPICE kernels provided in this data do not set the keyword INSTRUMENT_NAME to "SPICE KERNELS", that is the name of the instrument described by the instrument catalog file SPICE_INST.CAT provided in the data set. Instead this keyword is set to either "N/A" or the name(s) of the instrument(s) or structure(s), the geometric parameters of which a particular kernel file provides. While this error does prevent the individual data products from being associated with the "SPICE KERNELS" instrument, it does not affect usability of the SPICE data provided in this data set in any way because the SPICE toolkit does not use any information from the PDS label to access the data. The other side of this error is that the data set does not include an instrument catalog file for the following instruments named in the INSTRUMENT_NAME keyword in the CK file labels: "DEEP IMPACT FLYBY SPACECRAFT BUS" "HIGH GAIN ANTENNA" "DEEP IMPACT HIGH RESOLUTION INSTRUMENT - IR SPECTROMETER", "DEEP IMPACT HIGH RESOLUTION INSTRUMENT - VISIBLE CCD" "DEEP IMPACT MEDIUM RESOLUTION INSTRUMENT - VISIBLE CCD" 4. Missing FILE_RECORDS Keyword in the Binary Kernel Labels ----------------------------------------------------------- All labels for binary SPICE kernels provided in this data set are missing the FILE_RECORDS keyword, which is required because these labels have the RECORD_TYPE keyword set to FIXED_LENGTH. While this error violates the PDS standards, it does not affect usability of the SPICE data provided in this data set in any way because the SPICE toolkit does not use any information from the PDS labels to access the data. 5. Target Catalog Files ----------------------------------------------------------- No target catalog files are provided in this data set. The catalog files for the targets listed in the "mission.cat" are assumed to have already been ingested from the EPOXI science data sets. 6. SCLK Format ----------------------------------------------------------- The clock format defined by the SCLK kernels provided in this data set -- 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).