CASSINI SPK files =========================================================================== This ``aareadme.txt'' file describes contents of the kernels/spk directory of the CASSINI SPICE data server. It was last modified on September 11, 2007. 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 the data files provided in this directory. Brief summary -------------------------------------------------------- This directory contains the SPICE SP-Kernel files for the CASSINI orbiter spacecraft and probe trajectory and SP-Kernel file with planetary and satellite ephemerides used by the CASSINI project. All files are in IEEE binary format. Most of the files in this directory have been automatically copied from the CASSINI Project Database (DOM.) SPK File Naming Scheme -------------------------------------------------------- This section describes the CASSINI SPK file naming convention. It is divided into two parts, one for files created before May, 2003 and one for files created after that time. SPKs Produced by CASSINI NAV Team after May 2003. The SPK files produced by the CASSINI NAV team, after May 2003, are named as follows: [DeliveryDate][V][T]_[Description]_[StartEvent]_[EndEvent].[Ext] where: [DeliveryDate] Approximate date that the file was delivered (YYMMDD); [V] File version (optional, used only when applicable). It is specified as consecutive letters ``A'', ``B'', ``C'', etc. for each corresponding new version of the same file. [T] Type of the data in the file (optional, used only when applicable). If present, it is a single letter indicating predict trajectory file (``P'') or reconstructed trajectory file (``R''). [Description] File description. This field can be ``SK'' for orbiter spacecraft trajectory SPK file, ``OPK'' for orbiter and probe trajectory SPK file, ``PE'' for planetary ephemeris SPK file, ``SE'' for major satellite ephemeris SPK file, ``RE'' for minor satellite ephemeris SPK file, ``IRRE'' for outer irregular satellite ephemeris SPK file, or ``SCPSE'' for a merged S/C, Planetary and Satellite Ephemerides file. More file descriptors can be made up when necessary. Normally the new descriptors are limited to five characters. [StartEvent] Identifier of the file coverage start event. This field is a string consisting of two elements, , and , where represents the last two digits of the year in which the event started and is the day of the year. ``NA'' indicates not applicable. [EndEvent] Identifier of the file coverage end event. This field follows the same rules as the [StartEvent] field. [Ext] Standard SPICE extension for SPK files: ``bsp'' for binary SPK files, ``xsp'' or ``tsp'' for transfer format SPK files. For example, the file: 040901AP_SK_04192_05058.bsp is a binary SPK file delivered on 040901 (Sept. 1, 2004). It is the first version (A) of a Predicted SPK file covering from 2004 doy 192 to 2005 doy 058. Note that except where indicated, all file name components are required. The total number of characters in filenames should not exceed 30. Also note that a few reconstructed trajectory files delivered in 2005-2006 were named incorrectly. They had the version ([V]) and type ([T]) tokens swapped. These files are: 000331RB_SK_V1P32_V2P12.bsp 050105RB_SCPSE_04247_04336.bsp 050414RB_SCPSE_05034_05060.bsp 050513RB_SCPSE_05097_05114.bsp 061129RB_SCPSE_06292_06308.bsp SPKs Produced by CASSINI NAV Team prior to May 2003. The SPK files produced by the CASSINI NAV team, prior to May 2003, are named as follows: [DeliveryDate][V][T]_[Description]_[StartEvent]_[EndEvent].[Ext] where: [DeliveryDate] Approximate date that the file was delivered (YYMMDD); [V] File version (optional, used only when applicable). It is specified as consecutive letters ``A'', ``B'', ``C'', etc. for each corresponding new version of the same file. [T] Type of the data in the file (optional, used only when applicable). If present, it is a single letter indicating predict trajectory file (``P'') or reconstructed trajectory file (``R''). [Description] File description. This field can be ``SK'' for orbiter spacecraft trajectory SPK file, ``OPK'' for orbiter and probe trajectory SPK file, ``PE'' for planetary ephemeris SPK file, or ``SE'' for satellite ephemeris SPK file. More file descriptors can be made up when necessary. Normally the new descriptors are limited to two characters. More than two characters are allowed in cases where ``NA'' is placed as the [StartEvent] and [EndEvent] fields. [StartEvent] Identifier of the file coverage start event. This field is a string consisting of three sub-elements --

, , and -- described below. This field can also be set to ``NA'' value when this field is not applicable or to ``YYMMDD'' value to indicate start of the coverage for planetary and satellite ephemerides.

is a descriptor indicating planetary or satellite swingby. It can have any of the following values: ``L'' -- Launch, ``V1'' -- Venus1, ``V2'' -- Venus2, ``E'' -- Earth, ``J'' -- Jupiter, ``S'' -- Saturn, or the satellite's first letter or first two letters (in cases where there is a conflict) for the satellite tour. is used to denote timing in reference to a planetary or satellite swingby date. Use P for plus (after the swingby) or M for minus (before the swingby). is the number of days from closest approach date. [EndEvent] Identifier of the file coverage end event. This field follows the same rules as the [StartEvent] field. [Ext] Standard SPICE extension for SPK files: ``bsp'' for binary SPK files, ``xsp'' or ``tsp'' for transfer format SPK files. For example, the file: 971026AP_SK_LP15_SP0.bsp is a binary SPK file delivered on 971026 (Oct. 26, 1997.) It is the first version (A) of a Predicted SPK file covering from Launch plus 15 days to Saturn plus 0 days (or SOI). Other SPKs The SPKs that don't follows the naming scheme described in the previous section are special products created by NAV Team or NAIF. Some of these files -- the ones with the names starting with ``de'' and ``sat'' -- are planetary and satellite ephemerides SPK files. For the others, the file naming scheme is TBD. Supplementary/Meta Information Files -------------------------------------------------------- The only kind of supplementary/meta information files provided with the SPK files are detached label files. Label Files Detached label files have the same names as the corresponding SPK files with the additional extension ".lbl" appended at the end. The labels file do NOT have any specific structure and they contain rather ``raw'' information combined from the following sources: file SFDU label (if such was present), contents of the comment area, and summary of the file contents produced by BRIEF utility program. Most of these labels were created automatically "on the fly" and will be re-processed before final data archiving with the PDS.