Time Ephemerides / News: Recent posts

The JPL ephemeris data have been updated

The JPL planetary ephemerides represent some of 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). These original data are available in ascii form from ftp://ssd.jpl.nasa.gov/pub/eph/planets/ascii in uncompressed form, but as a convenience to users of the ephcom software package which manipulates and interpolates these data, I have redistributed the most important short JPL ephemerides and all long JPL ephemerides here (http://sourceforge.net/projects/timeephem/files/Compressed%20Ascii%20JPL%20Ephemerides) in compressed (bzip2) ascii form to save bandwidth.... read more

Posted by Alan W. Irwin 2013-02-05

te_gen-2.0.0 results have been released

This file release (http://sourceforge.net/projects/timeephem/files/Time%20Ephemerides/) contains ascii and binary time-ephemeris results that have been generated for most JPL and INPOP planetary ephemerides by the recently released te_gen-2.0.0 software. These results include the Newtonian (O(1/c^2)) and post-Newtonian (O(1/c^4)) components of a time-ephemeris integral evaluated at geocentre and the corresponding components of the time-ephemeris vector that helps determine the location-dependent correction to that integral for observation locations anywhere in the vicinity of the Earth. These combined results provide a superb approximation to the general-relativistic clock correction that must be made to determine the independent time variable of planetary (and time) ephemerides from Earth-based times such as TT (terrestrial time). Such results are also required to accurately interpret pulsar pulse arrival times or any other astronomical or spacecraft observation that requires accurate timing. Irwin and Fukushima (1999, http://articles.adsabs.harvard.edu/full/1999A&A...348..642I\) give important additional information concerning time ephemerides and Irwin (2013) is preparing an update to that paper to be consistent with the latest IAU time definitions (which are also used in the te_gen-2.0.0 implementation). When that research note is completed it will be linked from http://timeephem.sourceforge.net.... read more

Posted by Alan W. Irwin 2013-01-18

te_gen-2.0.0 has been released

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).... read more

Posted by Alan W. Irwin 2013-01-15

ephcom-3.0.0 has been released

The ephcom-3.0.0 software package that gives users convenient access to planetary and time ephemerides has just been released. New features of this release compared to ephcom-2.0.2 include the following: a convenient new high-level C API; new Fortran 95 and Python interfaces to that high-level API; an order of magnitude increase in speed; the ability to access INPOP ephemerides (in addition to the previously accessible JPL ephemerides); the ability to access time ephemerides; and the ability to access both planetary and time binary ephemerides in any endian order. 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 correctly predict the independent time variable of planetary ephemerides from TT (terrestrial time).... read more

Posted by Alan W. Irwin 2013-01-12

ephcom-2.0.2 has been released

The ephcom-2.0.2 software package that gives users convenient access to the JPL ephemerides, has been released. Those ephemerides (which are available in uncompressed form at ftp://ssd.jpl.nasa.gov/pub/eph/planets/ascii and in compressed form at http://sourceforge.net/projects/timeephem/files/Compressed%20Ascii%20JPL%20Ephemerides\) 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). The ephcom2 software allows the user to manipulate (e.g., convert from compressed or uncompressed ascii form to binary form) as well as interpolate (i.e., provide results at a given time) those ephemeris data in a well-documented (see http://timeephem.sourceforge.net/documentation.php\) way.... read more

Posted by Alan W. Irwin 2011-09-14

ephcom-2.0.1 has been released

ephcom-2.0.1, a software package that gives users convenient access to the JPL ephemerides, has been released. Those ephemerides (which are available in uncompressed form at ftp://ssd.jpl.nasa.gov/pub/eph/planets/ascii and in compressed form at http://sourceforge.net/projects/timeephem/files/Compressed%20Ascii%20JPL%20Ephemerides\) 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). The ephcom2 software allows the user to manipulate (e.g., convert from compressed or uncompressed ascii form to binary form) as well as interpolate (i.e., provide results at a given time) those ephemeris data in a well-documented (see http://timeephem.sourceforge.net/documentation.php\) way.... read more

Posted by Alan W. Irwin 2011-08-24

The JPL ephemeris data have been released

The JPL 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). These original data are available in ascii form from ftp://ssd.jpl.nasa.gov/pub/eph/planets/ascii in uncompressed form, but as a convenience to future users of the ephcom2 software package which manipulates and interpolates these data, I have redistributed the most important short JPL ephemerides and all long JPL ephemerides here (http://sourceforge.net/projects/timeephem/files/Compressed%20Ascii%20JPL%20Ephemerides) in compressed (bzip2) ascii form to save bandwidth.

Posted by Alan W. Irwin 2011-08-23