189 research outputs found

    Research and technology 81

    Get PDF
    During fiscal year 1981, the Goddard Space Flight Center continued to contribute to the goals and objectives of the Nation's space program by undertaking a wide variety of basic and applied research, technology developments, data analyses, applications investigations and flight projects. The highlights of these research and technology efforts are described

    Space Debris Mitigation CONOPS Development

    Get PDF
    Space debris remains an unsolved hazard for space operators and astronomers alike. Passive debris mitigation techniques have been enumerated and codified by the UNCOPUOS and IADC and several proposals for actively mitigating space debris have been presented. However, the space debris problem requires reframing. On the way to developing a viable CONOPS, a multi-disciplinary construct for building solution sets to tackle the space debris problem must be created. It must be shaped by building blocks of active and passive debris mitigation techniques, debris characterization and law. Central considerations must be taken. First, targeting of space debris for removal must be prioritized to unite effort and to make significant reductions in the space debris threat. Next, a leading agent must be identified and empowered to act as an executor for a space debris mitigation program, passive or active. Also needed is enactment of enforcement measures to ensure space faring nations comply with binding regulations. Lastly, active space debris mitigation programs must be urged along by the international community with contributions from all nations. Aside from monetary contributions, aid can be rendered via intellectual space and manpower. We must seek the right questions to effectively solve the space debris problem

    Energy and Spectral Efficient Wireless Communications

    Get PDF
    Energy and spectrum are two precious commodities for wireless communications. How to improve the energy and spectrum efficiency has become two critical issues for the designs of wireless communication systems. This dissertation is devoted to the development of energy and spectral efficient wireless communications. The developed techniques can be applied to a wide range of wireless communication systems, such as wireless sensor network (WSN) designed for structure health monitoring (SHM), medium access control (MAC) for multi-user systems, and cooperative spectrum sensing in cognitive radio systems. First, to improve the energy efficiency in SHM WSN, a new ultra low power (ULP) WSN is proposed to monitor the vibration properties of structures such as buildings, bridges, and the wings and bodies of aircrafts. The new scheme integrates energy harvesting, data sensing, and wireless communication into a unified process, and it achieves significant energy savings compared to existing WSNs. Second, a cross-layer collision tolerant (CT) MAC scheme is proposed to improve energy and spectral efficiency in a multi-user system with shared medium. When two users transmit simultaneously over a shared medium, a collision happens at the receiver. Conventional MAC schemes will discard the collided signals, which result in a waste of the precious energy and spectrum resources. In our proposed CT-MAC scheme, each user transmits multiple weighted replicas of a packet at randomly selected data slots in a frame, and the indices of the selected slots are transmitted in a special collision-free position slot at the beginning of each frame. Collisions of the data slots in the MAC layer are resolved by using multiuser detection (MUD) in the PHY layer. Compared to existing schemes, the proposed CT-MAC scheme can support more simultaneous users with a higher throughput. Third, a new cooperative spectrum sensing scheme is proposed to improve the energy and spectral efficiency of a cognitive radio network. A new Slepian-Wolf coded cooperation scheme is proposed for a cognitive radio network with two secondary users (SUs) performing cooperative spectrum sensing through a fusion center (FC). The proposed scheme can achieve significant performance gains compared to existing schemes

    Robust On-Manifold Optimization for Uncooperative Space Relative Navigation with a Single Camera

    Get PDF
    Optical cameras are gaining popularity as the suitable sensor for relative navigation in space due to their attractive sizing, power, and cost properties when compared with conventional flight hardware or costly laser-based systems. However, a camera cannot infer depth information on its own, which is often solved by introducing complementary sensors or a second camera. In this paper, an innovative model-based approach is demonstrated to estimate the six-dimensional pose of a target relative to the chaser spacecraft using solely a monocular setup. The observed facet of the target is tackled as a classification problem, where the three-dimensional shape is learned offline using Gaussian mixture modeling. The estimate is refined by minimizing two different robust loss functions based on local feature correspondences. The resulting pseudomeasurements are processed and fused with an extended Kalman filter. The entire optimization framework is designed to operate directly on the SE(3) manifold, uncoupling the process and measurement models from the global attitude state representation. It is validated on realistic synthetic and laboratory datasets of a rendezvous trajectory with the complex spacecraft Envisat, demonstrating estimation of the relative pose with high accuracy over full tumbling motion. Further evaluation is performed on the open-source SPEED dataset

    The 1981 NASA/ASEE Summer Faculty Fellowship Program: Research reports

    Get PDF
    Research reports related to spacecraft industry technological advances, requirements, and applications were considered. Some of the topic areas addressed were: (1) Fabrication, evaluation, and use of high performance composites and ceramics, (2) antenna designs, (3) electronics and microcomputer applications and mathematical modeling and programming techniques, (4) design, fabrication, and failure detection methods for structural materials, components, and total systems, and (5) chemical studies of bindary organic mixtures and polymer synthesis. Space environment parameters were also discussed

    Data analytics 2016: proceedings of the fifth international conference on data analytics

    Get PDF

    Autonomous Operation of a Reconfigurable Multi-Robot System for Planetary Space Missions

    Get PDF
    Reconfigurable robots can physically merge and form new types of composite systems. This ability leads to additional degrees of freedom for robot operations especially when dynamically composed robotic systems offer capabilities that none of the individual systems have. Research in the area of reconfigurable multi-robot systems has mainly been focused on swarm-based robots and thereby to systems with a high degree of modularity but a heavily restricted set of capabilities. In contrast, this thesis deals with heterogeneous robot teams comprising individually capable robots which are also modular and reconfigurable. In particular, the autonomous application of such reconfigurable multi-robot systems to enhance robotic space exploration missions is investigated. Exploiting the flexibility of a reconfigurable multi-robot system requires an appropriate system model and reasoner. Hence, this thesis introduces a special organisation model. This model accounts for the key characteristics of reconfigurable robots which are constrained by the availability and compatibility of hardware interfaces. A newly introduced mapping function between resource structures and functional properties permits to characterise dynamically created agent compositions. Since a combinatorial challenge lies in the identification of feasible and functionally suitable agents, this thesis further suggests bounding strategies to reason efficiently with composite robotic systems. This thesis proposes a mission planning algorithm which permits to exploit the flexibility of reconfigurable multi-robot systems. The implemented planner builds upon the developed organisation model so that multi-robot missions can be specified by high-level functionality constraints which are resolved to suitable combinations of robots. Furthermore, the planner synchronises robot activities over time and characterises plans according to three objectives: efficacy, efficiency and safety. The plannera s evaluation demonstrates an optimization of an exemplary space mission. This research is based on the parallel development of theoretical concepts and practical solutions while working with three reconfigurable multi-robot teams. The operation of a reconfigurable robotic team comes with practical constraints. Therefore, this thesis composes and evaluates an operational infrastructure which can serve as reference implementation. The identification and combination of applicable state-of-the-art technologies result in a distributed and dynamically extensible communication infrastructure which can maintain the properties of reconfigurable multi-robot systems. Field tests covering semi-autonomous and autonomous operation have been performed to characterise multi-robot missions and validate the autonomous control approach for reconfigurable multi-robot systems. The practical evaluation identified critical constraints and design elements for a successful application of reconfigurable multi-robot systems. Furthermore, the experiments point to improvements for the organisation model. This thesis is a wholistic approach to automate reconfigurable multi-robot systems. It identifies theoretical as well as practical challenges and it suggests effective solutions which permit an exploitation of an increased level of flexibility in future robotics missions

    Autonomous Operation of a Reconfigurable Multi-Robot System for Planetary Space Missions

    Get PDF
    Reconfigurable robots can physically merge and form new types of composite systems. This ability leads to additional degrees of freedom for robot operations especially when dynamically composed robotic systems offer capabilities that none of the individual systems have. Research in the area of reconfigurable multi-robot systems has mainly been focused on swarm-based robots and thereby to systems with a high degree of modularity but a heavily restricted set of capabilities. In contrast, this thesis deals with heterogeneous robot teams comprising individually capable robots which are also modular and reconfigurable. In particular, the autonomous application of such reconfigurable multi-robot systems to enhance robotic space exploration missions is investigated. Exploiting the flexibility of a reconfigurable multi-robot system requires an appropriate system model and reasoner. Hence, this thesis introduces a special organisation model. This model accounts for the key characteristics of reconfigurable robots which are constrained by the availability and compatibility of hardware interfaces. A newly introduced mapping function between resource structures and functional properties permits to characterise dynamically created agent compositions. Since a combinatorial challenge lies in the identification of feasible and functionally suitable agents, this thesis further suggests bounding strategies to reason efficiently with composite robotic systems. This thesis proposes a mission planning algorithm which permits to exploit the flexibility of reconfigurable multi-robot systems. The implemented planner builds upon the developed organisation model so that multi-robot missions can be specified by high-level functionality constraints which are resolved to suitable combinations of robots. Furthermore, the planner synchronises robot activities over time and characterises plans according to three objectives: efficacy, efficiency and safety. The plannera s evaluation demonstrates an optimization of an exemplary space mission. This research is based on the parallel development of theoretical concepts and practical solutions while working with three reconfigurable multi-robot teams. The operation of a reconfigurable robotic team comes with practical constraints. Therefore, this thesis composes and evaluates an operational infrastructure which can serve as reference implementation. The identification and combination of applicable state-of-the-art technologies result in a distributed and dynamically extensible communication infrastructure which can maintain the properties of reconfigurable multi-robot systems. Field tests covering semi-autonomous and autonomous operation have been performed to characterise multi-robot missions and validate the autonomous control approach for reconfigurable multi-robot systems. The practical evaluation identified critical constraints and design elements for a successful application of reconfigurable multi-robot systems. Furthermore, the experiments point to improvements for the organisation model. This thesis is a wholistic approach to automate reconfigurable multi-robot systems. It identifies theoretical as well as practical challenges and it suggests effective solutions which permit an exploitation of an increased level of flexibility in future robotics missions

    Economic efficiency and wealth prospects in the global network of countries

    Get PDF
    openIn recent years, the integration of physics into the economic field has proven to supply a deeper understanding of the complex web of interactions between the countries and the global markets, leading to a substantial development of the Econophysics branch of research. This work provides a contribution in this context through the characterization of the quantitative nexus which links the economic growth of the countries to the evolution over time of their trades and to the overall diversification of their commercial activity. The global trade system is effectively represented by a bipartite network, whose properties are investigated by means of a dynamic model consisting in a set of coupled stochastic differential equations and of a set of complexity measures derived from the celebrated Shannon's entropy function. The unification of these two methods of analysis provides a measure of the economic efficiency of the countries and leads to the realization of meaningful assessments of their wealth prospects. From the practical point of view, the theoretical models are implemented through proper Python and C++ codes.In recent years, the integration of physics into the economic field has proven to supply a deeper understanding of the complex web of interactions between the countries and the global markets, leading to a substantial development of the Econophysics branch of research. This work provides a contribution in this context through the characterization of the quantitative nexus which links the economic growth of the countries to the evolution over time of their trades and to the overall diversification of their commercial activity. The global trade system is effectively represented by a bipartite network, whose properties are investigated by means of a dynamic model consisting in a set of coupled stochastic differential equations and of a set of complexity measures derived from the celebrated Shannon's entropy function. The unification of these two methods of analysis provides a measure of the economic efficiency of the countries and leads to the realization of meaningful assessments of their wealth prospects. From the practical point of view, the theoretical models are implemented through proper Python and C++ codes
    corecore