As a consequence of the continuously increasing complexity of design, development and qualification of modern spacecraft subsystems, computer aided tools become increasingly important for solving the various engineering tasks in these fields.In the framework of development tasks for satellites and space stations, e.g. ERS-I/II, ROSAT, CLUSTER, SOHO, COLUMBUS-ECLSS, and HERMES a software environment has been developed at Dornier GmbH in recent years, which allows thermal analysis, thermal control and space environment control for system simulation as well as for detained component level simulation, monitoring and testdata evaluation. COSITHERM is a modular software package for the prediction of thermal radiation effects. SIMTAS can be used for detailed analysis of single system components as well as for the prediction of system response of arbitrarily connect components. The data acquisition, monitoring and analysis software system DIANA has been developed for thermal vacuum tests to monitor and maipulate measurement and analysis data. The modular approach provides several possibilities for data exchange between the modules.