In predictive geophysical model systems, uncertain initial values and model parameters jointly influence the temporal evolution of the system. As for chemistry-transport models, emission rates are at least as important as initial values for model evolution controls. This renders initial-value-only optimization by traditional data assimilation methods as insufficient. However, blindly extending the optimization parameter set jeopardizes the validity of the resulting analysis since the ill-posedness of the inversion task is increased. Hence, it becomes important to assess the potential observability of measurement networks for model state and parameters in atmospheric modelings in advance of the optimization. In this paper, we introduce an approach to quantify the impact of observation networks jointly for initial trace gas state and emission rates for transport-diffusion models extended by emissions. Applying a Kalman smoother as underlying assimilation technique, we develop a quantitative assessment method to evaluate the potential observability and the sensitivity of observation networks to initial values and emission rates. For practical applications, we derive an ensemble based version of the approach and give several elementary experiments for illustration.