Browsing by Subject "XNAV"

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    Inertially aided vector matching for opportunistic navigation in space
    (International Astronautical Federation, IAF, 2017-10) Runnels, Joel T; Gebre Egziabher, Demoz
    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.
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    Signal of Opportunity Time Difference of Arrival Estimation Using Adaptive Filtering Techniques
    (2017 IEEE Aerospace Conference, 2017) Runnels, Joel T.; Gebre-Egziabher, Demoz; Glesener, Lindsay
    EXACT and SOCRATES are a pair of CubeSats being developed to advance the TRL of a dual-use sensor. It can function either as x-ray detector used for characterization of high energy photons or as a sensor for measuring relative ranges between users in deep space operations. The ranging function of the sensor is described in this paper. After describing the measurements generated by the sensor, the algorithms that make use of this information to generate a position solution are presented. As a validation case study, data from the Japanese spacecraft Suzaku’s observation of the Crab Nebula Pulsar is used to estimate the spacecraft’s change in position along the line-of-sight to the pulsar, using this estimation scheme. Suzaku’s observations are suitable for this application because the spacecraft's Hard X-Ray Detector (HXD) is similar in effective surface area to the prototype X-Ray/gamma-ray detector currently under development for use onboard EXACTand SOCRATES. Thus, validation of this technique using data from Suzaku serves to verify the feasibility of this navigation technique onboard other spacecraft with detectors of similar size.