1. A computer-implemented method for estimating a parameter of an actual spacecraft based on a spectroscopic image of an emission from an atomic or molecular product of an interaction between an atmospheric gas and an atomic or molecular species in a plume from the actual spacecraft, the actual spacecraft being characterized by a set of values of at least N parameters, the method including: obtaining an N-dimensional lookup table stored in a non-transitory computer-readable medium, the lookup table storing information about a plurality of different simulated emissions, each simulated emission being from the atomic or molecular product of a simulated interaction between the atmospheric gas and the atomic or molecular species in a plume from a simulated spacecraft characterized by a corresponding set of values of the N parameters; selecting a simulated emission based on comparisons between the information about the simulated emissions and the spectroscopic image; and estimating a value of at least one of the N parameters of the actual spacecraft based on the selected simulated emission.