Deep Impact/EPOXI SPK files. =========================================================================== This ``aareadme.txt'' file describes contents of the kernels/spk directory of the Deep Impact/EPOXI SPICE data server. It was last modified on February 16, 2009. Contact Chuck Acton (818-354-3869, Chuck.Acton@jpl.nasa.gov) or Boris Semenov (818-354-8136, Boris.Semenov@jpl.nasa.gov) if you have any questions regarding this data. EPOXI SP-kernels Provided in This Directory ================================================= The following EPOXI SPK files are present in this directory. (Only the leading portions of the file names are shown; the file name extensions of the binary SPK files are always ".bsp"): spk_od* Regular OD solution SPKs produced by spk_drm* EPOXI NAV Team dif_epoch_nav_v1 SPK file providing DIF spacecraft trajectory as well as ephemerides of the comet Hartley 2 and solar system bodies for the whole duration of the EPOCh part of the EPOXI mission, made using the reconstructed OD SPK files produced during the EPOCh part (February 2006 to December 2008) of the EPOXI mission and the latest (as of December 2008) predicted SPK for the DIXI part of the EPOXI mission. Deep Impact SP-kernels Provided in This Directory ================================================= The following Deep Impact Flyby (DIF) and Impactor (DII) SPK files are present in this directory. (Only the leading portions of the file names are shown; the file name extensions of the binary SPK files are always ".bsp"): dif_preenc174_nav_v1 SPK file providing DIF spacecraft trajectory as well as ephemerides of the comets Tempel 1 and Boethin and solar system bodies for the whole duration of the mission, based on the last predict pre-encounter trajectory solution 174. dii_preenc174_nav_v1 SPK file providing DII spacecraft trajectory as well as ephemerides of the comets Tempel 1 and solar system bodies for the whole duration of the mission, based on the last predict pre-encounter trajectory solution 174. di_finalenc_nav_v1 SPK file providing an earlier version of the DIF, DII, and Tempel 1 trajectories for the two days period around encounter, reconstructed by DI NAV team from DIF and DII optical navigation data. DIF and DII spacecraft trajectories provided in this SPK use impact site as the center of motion. di_finalenc_nav_v3 SPK file providing the latest version of the DIF, DII, and Tempel 1 trajectories for the two days period around encounter, reconstructed by DI NAV team from DIF and DII optical navigation data. DIF and DII spacecraft trajectories provided in this SPK use impact site as the center of motion. di_finalenc_nav_v3_to06048 SPK file providing the latest version of the DIF, DII, and Tempel 1 trajectories for the two days period around encounter, reconstructed by DI NAV team from DIF and DII optical navigation data and then adjusted by Science Data Center, Cornell University to shift DIF and DII spacecraft trajectories to be with respect to the comet center rather than to the impact site. di_tempel1_ssd_v1.bsp SPK providing Tempel 1 ephemeris spanning from 2000 through 2050, produced at the end of the mission by the Solar System Dynamics Group at JPL. Comet ephemeris data provided in the file is the same as the data provided in di_finalenc_nav_v1, di_finalenc_nav_v3, and di_finalenc_nav_v3_to2006048 SPK files. NOTE 1: the best solution for processing the impact data is provided in the file di_finalenc_nav_v3_to2006048.bsp. NOTE 2: of the two NAV solutions providing spacecraft trajectories with respect to the impact site, the best one is in the file di_finalenc_nav_v3.bsp. di_finalenc_nav_v1.bsp SPK is included in the archive only because it was used to compute derived geometry items in the set of DI science products generated in November/December 2005. NOTE 3: the "preenc174" SPK files do not provide adequate accuracy for processing of the encounter image data. The encounter (for Impactor) and closest approach times (for Flyby) computed using spacecraft and comet trajectory provided in these SPKs are different from the actual times by over ten seconds. On the other hand these files provided trajectory spanning the whole mission and, therefore, cover every DIF and DII science observation that took place during cruise and far approach. NOTE 4: The following four of these SPKs should be loaded in this order to make sure that the best trajectory solutions are available to the calling application at any given time: dii_preenc174_nav_v1.bsp dif_preenc174_nav_v1.bsp di_tempel1_ssd_v1.bsp di_finalenc_nav_v3_to2006048.bsp EPOXI SPK File Naming Scheme ================================== The EPOXI SPKs provided in this directory are named according to the following scheme: TBD Deep Impact SPK File Naming Scheme ================================== The Deep Impact SPKs provided in this directory are named according to the following scheme: sc_ident_prod_vX[_modif].bsp where: sc is the name of the spacecraft: "dif" or "dii" or "di" (contains trajectory data for both spacecraft, Flyby and Impactor.) The exception to this is the file for Tempel 1 that provides data only for the comet but still has "di" as the first token indicating that the comet trajectory solution was derived primarily from Deep Impact mission observations. ident is a token identifying the type and coverage of trajectory data provided in the file. Examples: "preenc174" -- complete mission trajectory based on pre-encounter predicted trajectory OD solution 174; "postenc189" -- complete mission trajectory based on preliminary post-encounter trajectory solution 189; "finalenc" -- final reconstructed encounter trajectory, etc. prod is a token identifying the data producer. Examples: "nav" -- DI Navigation team, etc. vX is the file version number. modif is an optional modifier indicating additional processing done to create the file. Example: "to2006048" -- "t"empel "o"ffset, solution generated on 2006 DOY 048. 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 each SPK 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.