Observations of the troposphere in the millimeter wave region are of particular interest since some very important atmospheric trace gases are only accessible in this part of the electromagnetic spectrum. In the framework of European Space Agency (ESA) space programs for atmosphere chemistry analysis, a pre-phase A study of a new limb-sounder, MASTER (millimeter-wave acquisition for stratosphere/troposphere exchange research), has already started. One important task of this study is related to the development of a modular simulation program which generates antenna temperature maps, including Sun, Moon, Earth, atmosphere and cold space contributions, in order to define the future operative parameters of MASTER. This paper is aimed at describing the software tool and some simulation results.