This paper provides an overview of the improvements which are currently being made to ESA's MASTER model in preparation for the release of the new version, MASTER- 2009, in spring 2010. Within the current maintenance contract, improvements are being made to the population source models to account for new findings. Multi-Layered Insulation will be added as a new source for space debris based on a previously published model. The current paper highlights the background for the implementation of the model and changes which are being made to original model. On the user side of the tool, improvements will be made to allow a detailed investigation of individual fragmentation events. In the event of major fragmentation events which may pose a threat to operational satellites population files will be made available for download over the MASTER website. In addition, the current graphical user interface architecture will be revised. This will allow the current JAVA based user interface to be used for the online version of MASTER, replacing the current MARWIN interface.