Here follows a preliminary report on the construction of fake millimeter and sub-millimeter skies, as observed by virtual instruments, e.g. the COBRA SAMBA mission, using theo-retical modeling and data extrapolations. Our goal is to create maps as realistic as possible of the relevant p h ysical contributions which m a y contribute to the detected signals. This astrophysical modeling is followed by simulations of the measurement process itself by a given instrumental con guration. This will

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... le a precise determination of what can and cannot be achieved with a particular experimental con guration, and provide a feedback on how to improve the overall design. It is a key step on the way to de ne procedures for the separation of the di erent p h ysical processes in the future observed maps. Note that this tool will also prove useful in preparing and analyzing current e.g. balloon borne Microwave Background experiments.