European Space Agency

European Space Agency

Royal Belgian Institute for Space Aeronomy

Royal Belgian Institute for Space Aeronomy



The UNILIB library has been designed as a tool for the TREND project (Trapped Radiation ENvironment Development, ESA contracts 11711/95/NL/JG and 17025/94/NL/JG) by the Royal Belgian Institute for Space Aeronomy for The European Space Agency.

The main objectives of this project were to improve the radiation environment models and the software used to predict the radiation experienced by satellites and spacecraft in orbit around the Earth. To this effect, other coordinates than the widely used (B, L) coordinates are investigated to organise trapped particle fluxes, especially at low altitude.

The library provides tools to evaluate the new coordinates, which are related to interactions of particles with the environment, such as the atmospheric material encountered or the energy loss experienced by the trapped particles. The software library therefore implements tools to compute the geomagnetic field, to trace magnetic field lines and drift shells, to determine minimum mirror point altitudes and to evaluate averaged quantities along a drift trajectory.

The modules of the library have been written conform to Standard FORTRAN 77, extended to the use of STRUCTURE and RECORD statements, later replaced by FORTRAN 90 TYPE declarations. While most of the code uses essentially fixed-format FORTRAN 77 syntax, the use of FORTRAN 90 TYPE after version 2.09 requires a FORTRAN 90 compiler, which is ubiquitous even on older architectures.

Machine specific code has been avoided so that the library can be ported on a broad variety of platforms, under different operating systems.


The documentation of the library is provided in the form of HTML pages. The documentation contains a list of frequently asked questions, a list of all the components of the library, and a detailed description of each component. Some examples are provided as well.

Before working with the library, we strongly recommend to read the following documentation:


This file is subject to the terms and conditions defined in file LICENCE.TXT, which is part of this source code package. No part of the package, including this file, may be copied, modified, propagated, or distributed except according to the terms contained in the file ‘LICENCE.TXT’.

This file forms part of the UNILIB application, available from the European Space Software Repository (ESSR).