General information about SPICE PC-kernels ========================================== In the SPICE system, the PCK kernel provides orientation and ellipsoidal shape information pertaining to extended solar system bodies such as the Sun, the planets, the natural satellites of the planets, comets, and asteroids. The most recent generic PC kernel file based on the latest published IAU report can always be obtained from NAIF/JPL. The purpose of the PCK kernels and associated software is to provide SPICE users with a convenient mechanism for supplying planetary physical constants to application programs. SPICE PCK routines are able to read files conforming to the PCK format and return to a calling application program both the data contained in such files and a small number of commonly used numeric quantities derived from the kernel data. For information on the SPICE Toolkit and/or how to obtain it, please consult SPICE_INST.CAT and SOFT.CAT. Refer to the PCK.REQ document provided with the Toolkit to get more information on how to access PC-kernel data. Mars Express PCK Files ====================== This file describes the contents of the DATA/PCK directory of the Mars Express SPICE data set. PCK files in this directory are either binary or text files. Text files are created manually with the information from mainly the 2000 IAU Report. Binary files are created from the information contained in the EOP files provided by IERS All binary PCK files (*.BPC) contained in this directory are little-endian (LTL-IEEE) binary files. All text PCK files (*.TPC) contained in this directory are UNIX text files with lines terminated by only. Current PC-Kernels Contained in this Data Set ============================================= The following PCK-kernels are provided in this data set: DE403_MASSES.TPC SPICE Kernel (PCK) that contains the masses for the sun, planets, satellites and planetary barycenters. These masses are given as ratios of Solar GM to barycenter GM. PCKvvvvv.TPC SPICE Kernel (PCK) that contains the size, shape, radii and orientation constants for planets, satellites, Sun and some asteroids. In particular, data for Mars are contained in this file. vvvvv is the version number of the file. EARTH_[sdat]_[edat]_[pdat].BPC SPICE Kernel (PCK) that contains the orientation of the Earth as a function of time for the interval [sdat] to [edat]. From [pdat] the information contained in the file corresponds to predicted data. The rotational effects included are precession, nutation, rotation through true siderial time, polar motion and nutation corrections. 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. Kernel File Details =================== The most detailed description of the data in a text PCK file is provided in metadata included inside the description area of the file. This information can be viewed using any text editor program. The most detailed description of the data in a binary PCK file is provided in metadata 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 these kernels. The SPICE Toolkit provides versions in Fortran (SPICELIB), C (CSPICE), IDL (Icy), Matlab (Mice), and Java (JNISpice) and the user can choose any one that suits him/her. The SPICE routine FURNSH can be used to load a kernel file into a SPICE-based application to make kernel data usable with SPICE APIs. In the case when two or more binary PCK files contain data overlapping in time for a given object 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).