1. A method for estimating a state of a spacecraft in a planet-moon environment by executing iteratively a particle filter, each iteration of the particle filter comprising: integrating individually states of each particle of the particle filter according to a probability-evolution equation using a model of the state of the spacecraft represented as a planar circular restricted three-body problem (PCR3BP); determining a prior probability of each particle as a previous posterior probability of a corresponding particle during a previous iteration; determining a joint probability distribution of the state of the spacecraft using the states of each particle and the prior probabilities of each particle; and updating the states and the prior probabilities of each particle according to the joint probability distribution of the state of the spacecraft and a measurement of the state of the spacecraft to produce posterior probabilities of each particle, wherein steps of the method are performed by a processor.