Propagating EUV Solar Flux Uncertainty To Atmospheric Density Uncertainty

The call for realistic covariances/uncertainties in orbit determination/estimation and propagation is becoming louder. The main reason for unrealistic uncertainties is, in most cases, a disregard of force model uncertainties, i.e. the calculated covariances are based only on the measurement uncertainties. For this reason the covariances are often scaled in practice to avoid misjudgment of orbit knowledge. J. Emmert has recently shown how solar flux uncertainties can be propagated to in-track orbit position errors in the case of long-term orbit propagation. In his method, the density error resulting from solar flux errors is obtained via the underlying atmospheric model. In this paper, a universal analytic approximation of density uncertainty is presented, which is a fast, yet reliable, alternative to the case-based propagation via the atmospheric model. The major benefit of the proposed analytic estimations is that they seamlessly integrate with orbit estimation/propagation. The uncertainty estimate can directly be computed without an additional call to the atmospheric model.