At present there are few models for which the effect of time-varying parameters such as seasonal and diurnal changes in the solar zenith angle have been studied in detail. In particular, the possible effects on the model-estimated environmental impact of aerospace operations in the high atmosphere have not been reported in the literature. Using a one-dimensional model, we have studied the sensitivity to the time dependent variations of these parameters and its effect on the model-predicted perturbations. This sensitivity seems to limit the interpretability of steady state models.