Download INPOP06b


A. Fienga, H. Manche, J. Laskar and M. Gastineau, “INPOP06. A new numerical planetary ephemeris”, Astronomy & Astrophysics, 477, 2006, pp. 315-327.

Preprint: PDF file


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 ( 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)
TDB time scale
Time period
(years from J2000)
Little-endian files
(Intel or AMD x86, x86_64 or IA64 processors)
Big-endian files
(Motorola PowerPC, IBM Power or Sparc processors)
Value of KSIZE
(for the program “testeph.f”)
− 100 to 100 binary file (17 Mbytes) binary file (17 Mbytes) 1876
− 1000 to 1000 binary file (168 Mbytes) binary file (168 Mbytes) 1876


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.


For all comments concerning these pages, contact the authors:

Last update Wednesday 06 October 2021