Eterna, the 'Earth tide data processing package', was created by the late Prof. Hans-Georg Wenzel at the Black Forest Observatory and the University of Karlsruhe in the 1990s. This collection of programs established one standard of tidal analysis and prediction in the Earth tide community. Originally distributed only in the form of executable binaries, source code started to be distributed in the community after Hans-Georg Wenzel passed away in 1999.
Access to source code is essential in order to keep the program running on new computer platforms with recent compilers. Minor (and in a few cases major) modifications where applied by researchers to correct errors or support new features. This resulted in the unpleasant situation that different versions of the programs are circulated, where the relation to the original version is unclear (in particular with respect to source code modifications) and a clear statement is missing what holders of the source are allowed to do or not. Meanwhile (20 years after Eterna was first published) technical means are commonplace to publically distribute source code together with proper licensing and with each single modification being properly documented (such that the original author must not be blamed for mistakes introduced later).
In the belief that it would be in the intention of Hans-Georg Wenzel to support the continued use of Eterna in the tidal community, while allowing a clear distinction between current modifications and his original version and in the consent with his widow, Marion Wenzel, we publish the source code under terms of the GNU General Public License on a server of the Karlsruhe Institute of Technology (KIT) which is the successor of the University of Karlsruhe.
We present the software as now is available in a gitlab repository, documenting all changes applied to the original code. The software is complemented by data examples, which were distributed together with the original binary executable on CD-Rom.
https://gitlab.kit.edu/kit/gpi/bfo/tides/eterna
Wenzel, H.-G. (1996): The nanogal software: Earth tide data processing package ETERNA 3.30. Bulletin d'Informations Marees Terrestres, vol. 124, 9425-9439, Bruxelles 1996. http://www.bim-icet.org/ (last access: 2022-09-15)
Hartmann, T. and H.-G. Wenzel (1995): The HW95 tidal potential catalogue. Geophys. Res. Lett., vol. 22(24), 3553-3556. DOI: 10.1029/95GL03324
Wenzel, H.-G. (1997): Analysis of earth tide observations. In: Wilhelm, H., W. Zuern and H.-G. Wenzel (editors): Tidal phenomena, 59-76. Springer Verlag, Berlin 1997. DOI: 10.1007/BFb0011457
