THE NANOGAL SOFTWARE: EARTH TIDE DATA PROCESSING PACKAGE ETERNA 3.30. The new version 3.30 of the earth tide data processing package ETERNA is available since October 1st, 1996. The earth tide processing package ETERNA version 3.30 allows the recording, preprocessing and analysis of earth tide observations under operating system MS-DOS on an IBM-AT compatible personal computer 80386/387 upwards. The new standard format for the storage and exchange of high rate or high resolution earth tide data (Wenzel 1995) is used in all parts of the ETERNA 3.30 package. Compared to previous versions, we have included into the earth tide analysis package ETERNA (Wenzel 1994b,c) the most accurate tidal potential catalogue by Hartmannn and Wenzel (1995a,b). In all programs, the DUT1 correction due to the Earth’s variable rotation has been implemented using DUT1 values provided by the International Earth Rotation Service (IERS). Together with the Hartmann and Wenzel (1995a,b) tidal potential catalogue, this upgrade enables the preprocessing and analysis of earth tide observations and the prediction of earth tide signals with a model accuracy better than 1 ngal (1 ngal = 0.01 nm/s²). Several parts of the ETERNA earth tide analysis package have been rewritten and several other pieces have been added. For the computation of tidal signals, we have implemented recursion formulas which reduce the total computation time for some data sets down to 35% compared to previous versions without loss of accuracy. The computation of gravity variation due to polar motion and due to length of day variation from IERS data are implemented in the programs. The ETERNA package has benn given a new and better structure, and several programs have been renamed (e.g. the former program ETERNA has been renamed to ANALYZE, the former program ETGTAB has been renamed to PREDICT, the former program PRETERNA has been splitted into programs DETIDE, DESPIKE and DECIMATE). The program LOAD89 (provided by O. Francis) has been included, which enables the computation of ocean loading effects from different ocean tide models (Schwiderski 1980, CSR3.20, FES952). An on-line manual with search and export functions is provided to assist the user by his operations. We believe that a substantial improvement with respect to accuracy, flexibility and operational comfort has been achieved compared to previous versions of the package. ETERNA 3.30 is currently the only earth tide data processing package beeing able to process earth tide observations with a model accuracy better than 1 ngal.