PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 2008-12-30 NOTE = "This file describes the files in the EXTRAS/MK directory of this archive." END_OBJECT = TEXT END Meta-kernels for the Mars Express mission ========================================= This directory contains the meta-kernel files (a.k.a "furnsh" files) that provide lists of the archived kernels included in this data set suitable for loading into a SPICE-based application via the high level SPICE data loader routine FURNSH. Using these meta-kernels makes it easy to load with one call a comprehensive SPICE data collection for a given period. Like the text kernels archived in this data set, these meta-kernels are UNIX text files that have lines terminated with a line feed character, LF (ASCII 10). The names of the meta-kernels provided in this directory follow these two patterns: MEX_Vvv.TM MEX_YYYY_Vvv.TM where ``vv'' is the file version and ``YYYY'' is the four digit year to which the meta-kernel applies. Each of the ``MEX_Vvv.TM'' meta-kernels lists kernels for the whole mission. Unfortunately, because of the large numbers of segments in the MEX SPK and CK files produced from ESOC Ancillary Data files, the total numbers of SPK and CK segments in all SPK and CK kernels listed in a meta-kernel of this kind can exceed the size of the SPICE internal SPK and CK segment buffers, causing severe degradation in SPICE system performance. For this reason using these meta-kernels is not recommended. Each of the``MEX_YYYY_Vvv.TM'' meta-kernels lists only kernels for a given year, thus reducing the total number of SPK and CK segments loaded at once. Using these meta-kernels individually does not lead to decreased performance in SPK and CK subsystems of the SPICE system. Multiple versions of a meta-kernel for the data set may exist if new kernels were added to the archive in a later release and the meta-kernel had to be updated to incorporate them. The reasons for adding new kernels include (but are not limited to) adding new kinds of kernels, adding new versions of existing kernels containing more complete or more accurate data, and adding new versions of existing kernels superseding the existing kernels that had errors. If more than one meta-kernel file is present, then the file with the latest version number supersedes all earlier versions. Although the meta-kernels were created such that on a UNIX workstation they can be loaded into a SPICE-based application directly from the root directory of the data set -- because the PATH_VALUES keyword is set to './DATA' and '/' is used as the path delimiter -- it is recommended that users make local copies of these files and update the PATH_VALUES keyword in each of them to point to the actual location of the data set's 'data' directory on their system. Additional changes including replacing '/' and '\' in all path specifications and converting UNIX line terminator to terminators native to the user's system may be required to use these meta-kernels on non-UNIX workstation. The following guidelines were followed to pick and set priority -- determined by the order in which the kernel files are listed, with the latest one taking precedence -- for the kernel files included in these meta-kernels: - the latest archived versions of LSK, SCLK, IK, FK, PCK, SPK and CK were included - The latest JPL MAR63 satellite ephemeris were preferred to other satellite ephemeris - There are two families of SPK kernels with ephemeris information for Mars Express, one created by the ROB, and one created by ESOC. Any of them can be used, although the second one is the option used in the meta-kernels. Should the user want the other set of kernels, he/she should replace the ESOC kernels by them. Note that the kernels provided by ROB might span a smaller period of time - both the predicted and reconstructed spacecraft orientation CKs were included with the reconstructed CKs taking precedence (listed last) and predicted CKs having lower priority and used when the reconstructed CKs do not provide coverage - no EK files were included since ESA don't produce EK kernels for their missions Contact Information =================== Regarding Mars Express project specific information provided in this data set and for general information about SPICE system, contact: Jose Luis Vazquez-Garcia +34 91 813 1310 jvazquez@rssd.esa.int , or Boris Semenov (818)-354-8136 Boris.Semenov@jpl.nasa.gov