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As near-Earth space becomes more populated with large constellations of satellites and research into spacecraft autonomy and disaggregation becomes more prevalent, it will be increasingly important to design effective communication procedures between satellites to efficiently share resources and avoid collisions. Though there have been several space networking simulation tools created in recent years, they all lack rigorous astrodynamics models or use high-fidelity but bulky and computationally taxing commercial software. This research presents Spacecraft-ns3, an extension to the ns-3 network simulator. Using a modular approach, Spacecraft-ns3 propagates orbit state, plans discrete events, and analyzes network metrics and flows. A case study using Spacecraft-ns3 is presented for exploratory space network analysis. / Master of Science / Near-Earth space has become more crowded in recent years due to the increasing number of large constellations of satellites in this region. Autonomous vehicle research has been applied to Earth satellites primarily to share power and computing resources between satellites, or to prevent collisions between satellites. Both of these factors require effective communication procedures between satellites, which can be inexpensively simulated with network simulators. However, network simulators are primarily designed for ground-based use, and must be combined with an astrodynamics simulator to effectively simulate satellite networks. This research presents Spacecraft-ns3, an integrated simulator that defines spacecraft orbits and attitude, and analyzes network activity. This simulator improves upon prior simulation efforts by extending the ns-3 network simulator with efficient and high-fidelity astrodynamics models. The Spacecraft-ns3 simulator is demonstrated in an exploratory case study.

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International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Spacecraft communication simulators are extremely useful for integration and testing of spacecraft control centers and supporting ground systems. To reduce development costs, a Windows NT PC-based simulation system is being developed to support testing for upcoming NASA missions. The spacecraft simulation suite of tools integrates modules within a core infrastructure and is customized to meet mission unique specifications not met by the baseline system.

Recent years have seen ambitious robotic exploration missions to other planets and a renewed interest in sending humans beyond low Earth orbit. These activities give rise to a need for autonomous spacecraft operation. Of particular interest here is the ability of a spacecraft to navigate independent of contact with Earth-based resources. Optical navigation techniques are proposed as a solution to the problem of navigating in a planetary system without requiring navigation information from Earth. A detailed discussion of optical sensor hardware and error sources leads to new high fidelity math models for optical sensor performance that may be used in navigation simulations. Algorithms are developed that allow optical data to be used for the estimation of spacecraft position, velocity, and attitude. Sequential measurements are processed using traditional filtering techniques. Additionally, for the case of attitude estimation, a new attitude filter called Sequential Optimal Attitude Routine (SOAR) is presented. The models and techniques developed in this dissertation are demonstrated in two case studies: (1) navigation of a spacecraft performing a planetary fly-by using real images from the June 2007 MESSENGER fly-by of Venus and (2) navigation of a spacecraft in cislunar space on a return trajectory from the Moon. / text

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This discussion is concerned primarily with communications blackout during spacecraft entry into a planetary atmosphere. The gas in the shock layer, between shock wave and vehicle surface, ionizes from the intense heating which takes place in the bow shock wave and a viscous region of high gas enthalpy. This ionization may persist throughout the subsequent flow over the vehicle and into the wake, thus completely engulfing the vehicle and its communications elements. The problem will be to simulate a plasma model that will be of interest for hypervelocity reentry vehicles and to provide meaningful expressions for the various plasma parameters of interest (electron density, electron temperature, collision frequency, etc.) in terms of the microwave measurables (amplitude, phase shifts, frequency shifts, polarization, etc.)