General information about SPICE SP-kernels ========================================== The purpose of the SP-kernel -- which stands for S(pacecraft) and P(lanet) Kernel -- is to allow ephemeris for any collection of solar system bodies, spacecraft or any other objects in 3D space to be combined under a common file format, and accessed by a common set of subroutines. SPK can be accessed by subroutines that are part of the SPICE library, the major component of the SPICE Toolkit. These subroutines can be integrated into user application programs. For information on the SPICE toolkit and/or how to obtain it, please consult SPICE_INST.CAT and SOFT.CAT. To use SP-kernels, a Leapseconds (LSK) is also required. To use SP-Kernels containing positions given relative to the non-inertial and project-defined frames, Frame Definitions Kernel (FK), Planetary Constants Kernel (PCK), and C-Kernel (CK) files are also required. Refer to the SPK.REQ document provided with the Toolkit to get more information on how to access SP-kernel data. Venus Express SPK Files ======================= This file describes the contents of the DATA/SPK directory of the Venus Express SPICE data set. Sources of kernels and naming convention: ---------------------------------------- - Kernels that are produced from the ESOC Flight Dynamics orbit products. These kernels are generated by an automated system located at ESAC, and operated by the ESAC SPICE Team. The naming convention for these kernels is the same used in the Attitude products used to create them; their file name start by OR. - Kernels that store information about Solar System bodies, ground stations, etc. They are produced by NAIF/JPL, and keep their original name, but in capitals, to be PDS compliant. The contents and time span covered by any SPK file may be easily determined using the 'brief' utility program available in all copies of the SPICE Toolkit. Examples of usage: %brief %brief <*.bsp> %brief Descriptive information about how/why/when an SPK file was created is usually available in the 'comment area' of the file. This may be viewed using the 'commnt' utility program available in all copies of the SPICE Toolkit. Use the '-r' option to read the comments. Example: %commnt -r All binary SPK files (*.BSP) contained in this directory are UNIX binary files. These may be used as is (without format conversion) in a non-UNIX environment when using any recent version of the SPICE Toolkit (Version N0052 or later). Venus Express SPK-Kernels Contained in this Data Set =================================================== The following SPK-kernels are provided in this data set: DE405.BSP This file contains ephemeris data for the main Solar System bodies (planets barycenters, Mercury, Venus, Moon, Earth, Mars and Sun). It covers from Jan. 1950 to Jan. 2050. EARTHSTNS_FX_yymmdd.BSP Contains ephemeris data for NASA DSN stations relative to the terrestrial reference frame ITR93. In the interest of flexibility, in this file the reference frame is labelled with the alias 'EARTH_FIXED'. Any application using this file must map the alias 'EARTH_FIXED' to either 'ITR93' or 'IAU_EARTH'. This file was released on yy-mm-dd. EARTHSTNS_ITRF93_yymmdd.BSP Contains ephemeris data for NASA DSN stations relative to the terrestrial reference frame label 'ITR93'. This file was released on yy-mm-dd. NEW_NORCIA.BSP Ephemeris data for the ESA New Norcia Ground station. ORHV_______________vvvvv.BSP Ephemeris data for Venus Express, centered in the Sun, for the Cruise Phase (from Jun. 2, 2003 to Dec. 22, 2003). ORVV__YYMM01000000_vvvvv.BSP Ephemeris actual data for Venus Express. YYMM is the month for which the file provides coverage, and vvvvv is the version number of the file. Note that several versions of the same kernel can be provided. In that case, the file with the highest version number is the most up to date, and the one that should be used. Note: Files EARTHSTNS_FX_yymmdd.BSP and EARTHSTNS_ITRF93_yymmdd.BSP contain the same data. These files only differ in that the second one use the reference frame label 'ITR93' instead of 'EARTH_FIXED'. 'EARTH_FIXED' alias must be map to either 'ITR93' or 'IAU_EARTH' before using the file. For high accuracy work, EARTHSTNS_ITRF93_yymmdd.BSP is recommended (on the basis of ease of use). Kernel File Details =================== The most detailed description of the data in each SPK file is provided in meta data included inside the comment area of the file. This information can be viewed using utility programs COMMNT and SPACIT included in the SPICE Toolkit. At least a basic knowledge of the SPICE system is needed in order to use this kernels. The SPICE toolkit provides versions in FORTRAN (SPICELIB), C (CSPICE), IDL (icy) and Matlab (mice), and the user can choose any one that suits him/her. The SPICELIB routine FURNSH, CSPICE function furnsh_c, and icy/mice routine cspice_furnsh load a kernel file into the kernel pool as shown below. CALL FURNSH( 'kernel_name' ) furnsh_c( ''kernel_name'' ); cspice_furnsh, 'kernel_name' cspice_furnsh( 'kernel_name' ); In the case when two or more files contain data overlapping in time for a given object, for binary kernels, the file loaded last takes precedence. If two (or more) text kernels assign value(s) using the '=' operator to identical keywords, the data value(s) associated with the last loaded occurrence of the keyword are used -all earlier values have been replaced with the last loaded value(s).