Time Ephemerides Files

This is a release of compressed ascii results for time ephemerides generated by the te_gen-2.0.0 software from a wide variety of JPL and INPOP planetary ephemerides.  Note, these results can only be manipulated and interpolated by ephcom-3.0.0 software.
 
These results include the Newtonian (O(1/c^2)) and post-Newtonian (O(1/c^4)) components of the time-ephemeris integral and the corresponding components of the time-ephemeris vector that helps determine the location-dependent correction to that integral.  However, these results do not include the direct effect of asteroids since normally the exact adopted asteroid ephemeris that helps to determine the calculations of planetary ephemerides is not made publicly available with planetary ephemeris results.  The missing direct asteroid effect amounts to a correction to these time ephemerides consisting of a sum of quasi-periodic terms whose combined amplitudes rarely exceed 15 ps and a secular trend with a dimensionless slope near 5.e-18.  These errors are so small they can probably be judged to be negligible for most if not all users' needs.  Nevertheless, I call on all those groups publicly distributing planetary ephemerides to also publicly distribute the corresponding asteroid ephemerides in the interests of open science (since how the asteroids are modelled is an important factor distinguishing the quality of one planetary ephemeris calculation compared to another) and in the interests of removing this source of error from te_gen calculations.

When downloading these tarball (*.tar) files containing compressed ascii versions of time ephemerides remember also to download the separate armoured ascii signature files (*.tar.asc).  You may verify every bit is correct in the download and the files are signed by me (Alan W. Irwin) by running the command

gpg --verify $TARBALL.asc

where $TARBALL is the filename of the tarball and $TARBALL.asc is the corresponding separate armoured ascii signature filename.  A good verification result should identify the key id as 

key ID BB159E92

and include the line

gpg: Good signature from "Alan W. Irwin (Time Ephemerides key) <airwin@users.sourceforge.net>"

The tarballs contain 3 files, e.g., 

-rw-r--r-- software/software 971 2013-01-14 18:35 ./te422/te_header.422
-rw-r--r-- software/software 4670458 2013-01-14 19:52 ./te422/te_testpo.422
-rw-r--r-- software/software 150540657 2013-01-14 19:23 ./te422/te_asc.422.bz2

which normally would be converted to a binary ephemeris te422/TE_EPH (with the endianness of the hardware platform automatically chosen as the endianness of that binary file) and checked as follows:

bunzip2 -c < te422/te_asc.422.bz2 |\
ephcom_asc2eph te422/te_header.422 - te422/TE_EPH

ephcom_testeph te422/TE_EPH te422/te_testpo.422 |less

Finally, C, Fortran 95, or Python applications written by the user should use the standard high-level API for ephcom-3.0.0 (see examples/c/test_api.c, f95/test_api.f, and examples/python/test_api.py that demonstrate use of this API) to read constants from the header of the binary time ephemeris or interpolate time ephemeris data using Chebyshev coefficients stored in the binary ephemeris at any time specified by the user that is within the epoch range of the time ephemeris.  Such interpolated time-ephemeris data are useful for determining the precise independent variable of both planetary and time ephemerides as a function of TT (terrestrial time) or reducing pulsar pulse arrival times or any other astronomical or spacecraft observation that requires precise timing.