The te_gen-2.0.0 software package that allows users to generate time ephemerides from planetary ephemerides has just been released. New features of this release compared to te_gen-1.0.0 (released in 1999) include the following: a CMake-based build system that makes it convenient to build, install, and test the software; improved documentation, a factor of 3 improvement in speed based on use of the Fortran 95 capabilities of ephcom-3.0.0 to interpolate at a given time all required planetary ephemeris results with one efficient call to the ephcom_interpolate_list routine (rather than using inefficient multiple calls to DPLEPH or its modern equivalent to interpolate required planetary ephemeris results one solar-system object at a time); the ability to generate time ephemerides from both INPOP and JPL planetary ephemerides (as opposed to just from JPL planetary ephemerides for the old version of the code); a Fortran 95 interface; and implementation of O(1/c^4) corrections to the time-ephemeris integral evaluated at geocentre and the corresponding corrections to the time-ephemeris vector that helps correct that geocentre result to any observation location near the geocentre. Planetary ephemerides represent mankind's best knowledge of the positions and velocities of all major bodies of the solar system over centuries (short ephemerides) and millennia (long ephemerides). Time ephemerides are computed from planetary ephemerides and represent mankind's best knowledge of the general relativistic corrections that must be made to clocks that are located near some reference point within the solar system (e.g., some point near the Earth). Such clock corrections are required, for example, to determine an accurate independent time variable of planetary ephemerides from TT (terrestrial time).
The te_gen-2.0.0 development effort which is part of the Time Ephemerides Project (http://timeephem.sourceforge.net) is a revival of the te_gen-1.0.0 software which was released in 1999 as a companion software to the paper by Irwin and Fukushima (1999, http://articles.adsabs.harvard.edu/full/1999A&A...348..642I\) which provides useful scientific background for the calculation and use of time ephemerides. Work is in progress on a research note that updates Section 2 of that paper to be consistent with IAU definitions introduced since 1999. (http://timeephem.sourceforge.net will link to that research note when it is completed.) The te_gen-2.0.0 release represents a substantial (~200 commits) improvement on te_gen-1.0.0, is licensed under the LGPL, and may be downloaded from http://sourceforge.net/projects/timeephem/files/te_gen. That same location also gives access to release notes and a detailed ChangeLog for te_gen-2.0.0.