In this work, an estimator is developed for the joint estimation of orientation and position from astrophysical signals of opportunity, particularly pulsars. The filter is based on a combination of vector-matching techniques for estimating attitude and time-difference of arrival navigation for estimating position. The filter functions by computing the probability of association for each arriving photon with each signal source of interest, and using the association probabilities to perform the measurement update. The probability of association of a photon with a signal source is derived, as well as the probability of association with background. The estimation techniques proposed are tested using Monte Carlo analysis techniques. The accuracy of the resulting estimates is compared to other pulsar navigation techniques. The results of the simulation studies indicate that the technique proposed here generally outperforms other time difference of arrival estimation techniques.