The MAST has successfully demonstrated an end-to-end simulation process that can quantitatively evaluate the science impacts of instrument concepts and sampling strategies by integrating the OSSE system, the GCA system, and the SOX system (see Figure 10). The end-to-end process is organized with four stages of (1)observation scenario exploration, (2)measurement quality exploration, (3)measurement quality evaluation, and (4)observation scenario evaluation employing forward models, system performance simulations, and inverse methods. The first two stages enable scientists to formulate and explore measurement requirements while the last two stages enable scientists to validate and optimize them against science objectives and design processes. The four stages are streamlined by infusing a wide range of information technologies including on-line services, distributed database management, and parallel computing.