The orbital solutions of the Sun, the eight planets, the dwarf planet Pluto and the Moon and the libration of the Moon are available as binary data files.
The binary data files provide the rectangular coordinates (x,y,z) in kilometers of the bodies with respect to the International Celestial Reference Frame (ICRF). These orbital solutions are expressed in the TDB time scale. The librations are given in radians.
These INPOP06b ephemeris files are provided in the following file format
Binary files compatible with the JPL file format
These INPOP06b ephemeris files use the same internal format as the binary JPL DExxx ephemeris files (http://ssd.jpl.nasa.gov/?ephemerides) : the coordinates in the data files are expressed as the coefficients of the Chebychev polynomials. These files provide the orbital solution expressed in the TDB time scale. These files don't include the coefficients for the nutation and the time scale transformation TT-TDB. So these files could be read with the same programs (such as the JPL software package) which read the binary JPL ephemeris files.
The internal format is described in the paper :
David Hoffman : 1998,
A Set of C Utility Programs for Processing JPL Ephemeris Data,
Due to the problem of the endianess in the computer (order in which integers are stored as bytes in computer memory), the binary files are available into two formats :
- little-endian for Intel x86, IA64 or Alpha based processors (and their clones).
- big-endian for Motorola PowerPC, IBM Power or Sparc based processors (and their clones).
To use these data files instead of the JPL ephemeris files, you only have to change the name of the files in your software program.
If you use a program based on the "testeph.f" program from the JPL, then you may have to set the variable NRECL (and KSIZE if you don't use the subroutine FSIZER2). The prefered method is to read the beginning of the first record and then to compute the length of the records (same as KSIZE) with the libration's triplet (which contains the location, order and time-coverage of Chebychev polynomial).
We provide the open-source CALCEPH Library, which provides a compatible C, Fortran and Python Application Programming Interface. This library avoids the problems with the variables (NRECL and KSIZE) and the endianess. It supports the access to the multiple ephemeris files at the same time.
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Last update Thursday 07 September 2017