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At least 1,279 records · Page 71
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NASA NTRSDate not supplied

Toward Design Assurance of Machine-Learning Airborne Systems

In recent years, Artificial Intelligence (AI) systems, enabled by Machine Learning (ML)technology, have demonstrated impressive progress and provides historic opportunities for the aviation industry. However, several key aspects of ML technology are not compatible with existing design assurance standards and make certification problematic. In this paper, we present a case study of a visual system with a Deep Neural Network (DNN) intended to detect and identify airport runway signs. Different use cases and variants of this system exhibit different levels of criticality ranging from design assurance level (DAL) D to B. We use the case study to illustrate the challenges of certification according to the current standards, such asDO-178C. We present the system design, data generation, training, and verification in detail and describe how the design assurance objectives can be met for a DAL D variant of the system. We also discuss gaps and potential approaches for the higher design assurance levels.

Avionics↗
NASA NTRS1977

A GSTDN/TDRSS compatible RF system for the Solar Maximum Mission /SMM/

The Solar Maximum Mission (SMM) is a major NASA observatory to be launched in late 1979. SMM will be supported by NASA's existing Ground Spaceflight Tracking and Data Network (GSTDN) and the planned Tracking and Data Relay Satellite System (TDRSS). Design of a GSTDN/TDRSS compatible RF system for SMM poses multiple problems related to the complex nature of the observatory command, telemetry, and tracking support requirements and the fundamental differences in signal design, antenna characteristics, data rates, and link performance criteria for GSTDN vs. TDRSS support. The RF system described in this paper achieves full compatibility with a minimum of hardware complexity by use of an integrated antenna system, the NASA standard S-Band transponder, and utilization of both the single access and multiple access support capabilities of the TDRSS to handle both real time data and tape recorder dumps.

Heffernan, P. J.↗
NASA NTRS1981

Design and fabrication of a stringer stiffened discrete-tube actively cooled panel for a hypersonic aircraft

A 0.61 x 1.22 m (2 x 4 ft) test panel was fabricated and delivered to the Langley Research Center for assessment of the thermal and structural features of the optimized panel design. The panel concept incorporated an aluminum alloy surface panel actively cooled by a network of discrete, parallel, redundant, counterflow passage interconnected with appropriate manifolding, and assembled by adhesive bonding. The cooled skin was stiffened with a mechanically fastened conventional substructure of stringers and frames. A 40 water/60 glycol solution was the coolant. Low pressure leak testing, radiography, holography and infrared scanning were applied at various stages of fabrication to assess integrity and uniformity. By nondestructively inspecting selected specimens which were subsequently tested to destruction, it was possible to refine inspection standards as applied to this cooled panel design.

Anthony, F. M.↗
NASA NTRS1983

Preliminary design of 19-element feed cluster for a large F/D reflector antenna

The design of a low sidelobe 19 element microstrip cluster and its distribution network is described. The problem of spillover illumination of an adjacent reflector in a multiple aperture reflector system is addressed. A practical implementation of the array is presented which requires only one printed circuit board for the distribution network with the potential for being easily tailored to a wide range of excitation distributions.

Bailey, M. C.↗
NASA NTRS1982

Space station communications and tracking equipment management/control system

Design details of a communications and tracking (C and T) local area network and the distribution system requirements for the prospective space station are described. The hardware will be constructed of LRUs, including those for baseband, RF, and antenna subsystems. It is noted that the C and T equipment must be routed throughout the station to accommodate growth of the station. Configurations of the C and T modules will therefore be dependent on the function of the space station module where they are located. A block diagram is provided of a sample C and T hardware distribution configuration. A topology and protocol will be needed to accommodate new terminals, wide bandwidths, bidirectional message transmission, and distributed functioning. Consideration will be given to collisions occurring in the data transmission channels.

Kapell, M. H.↗
NASA NTRS1985

The science of computing - Parallel computation

Although parallel computation architectures have been known for computers since the 1920s, it was only in the 1970s that microelectronic components technologies advanced to the point where it became feasible to incorporate multiple processors in one machine. Concommitantly, the development of algorithms for parallel processing also lagged due to hardware limitations. The speed of computing with solid-state chips is limited by gate switching delays. The physical limit implies that a 1 Gflop operational speed is the maximum for sequential processors. A computer recently introduced features a 'hypercube' architecture with 128 processors connected in networks at 5, 6 or 7 points per grid, depending on the design choice. Its computing speed rivals that of supercomputers, but at a fraction of the cost. The added speed with less hardware is due to parallel processing, which utilizes algorithms representing different parts of an equation that can be broken into simpler statements and processed simultaneously. Present, highly developed computer languages like FORTRAN, PASCAL, COBOL, etc., rely on sequential instructions. Thus, increased emphasis will now be directed at parallel processing algorithms to exploit the new architectures.

Denning, P. J.↗
NASA NTRS1987

Analysis of a Four-Reflector S/X-Band Antenna

Physical optics accounts for near field, cross polarization, and higher-order modes. Report presents physical-optics analysis of four-reflector, 64-m antennas of Deep Space Network. Analysis thorough and detailed. Report has instructional value as example for designers of large microwave dishes with subreflectors and involving reflector surfaces with hyperboloidal, paraboloidal, ellipsoidal, and more complex shapes.

Cha, Alan G.↗
NASA NTRS1989

Marshall Avionics Testbed System (MAST)

Work accomplished in the summer of 1989 in association with the NASA/ASEE Summer Faculty Research Fellowship Program at Marshall Space Flight Center is summarized. The project was aimed at developing detailed specifications for the Marshall Avionics System Testbed (MAST). This activity was to include the definition of the testbed requirements and the development of specifications for a set of standard network nodes for connecting the testbed to a variety of networks. The project was also to include developing a timetable for the design, implementation, programming and testing of the testbed. Specifications of both hardware and software components for the system were to be included.

Smith, Wayne D.↗
NASA NTRS1991

Alternative AlxGa1-xAs/GaAs Transistors For Neural Networks

Further development efforts yield alternative version of transistors described in "High-Gain AlxGa1-xAs/GaAs Transistors For Neural Networks" (NPO-18101). Efforts focused on determining effects of various aspects of design and of fabrication processes upon leakage currents and on current gain.

Kim, Jae-Hoon↗
NASA NTRS1990

Digital frequency synthesizer for radar astronomy

The digital frequency synthesizer (DFS) is an integral part of the programmable local oscillator (PLO) which is being developed for the NASA's Deep Space Network (DSN) and radar astronomy. Here, the theory of operation and the design of the DFS are discussed, and the design parameters in application for the Goldstone Solar System Radar (GSSR) are specified. The spectral purity of the DFS is evaluated by analytically evaluating the output spectrum of the DFS. A novel architecture is proposed for the design of the DFS with a frequency resolution of 1/2(exp 48) of the clock frequency (0.35 mu Hz at 100 MHz), a phase resolution of 0.0056 degrees (16 bits), and a frequency spur attenuation of -96 dBc.

Sadr, R.↗
NASA NTRS1990

Modeling of the Space Station Freedom data management system

The data management system (DMS) is the information and communications system onboard Space Station Freedom. Extensive modeling of the DMS is being conducted throughout NASA to aid in the design and development of this vital system. Activities to model the DMS network infrastructure are described, focusing on modeling of the fiber distributed data interface (FDDI) token-ring protocol and experimental testbedding of networking aspects of the DMS.

Johnson, Marjory J.↗
NASA NTRS1991

A Common Lunar Lander (CLL) for the Space Exploration Initiative

Information is given in viewgraph form on the Artemis project, a plan to establish a permanent base on the Moon. Information includes a summary of past and future events, the program rationale, a summary of potential payloads, the physical characteristics of experiments, sketches of equipment, design study objectives, and details of such payloads as the Geophysical Station Network, teleoperated rovers, astronomical telescopes, a Moon-Earth radio interferometer, very low frequency radio antennas, the Lunar Polar Crater Telescope, Lunar Resource Utilization Experiments, and biological experiments.

Bailey, Stephen↗
NASA NTRS1992

ACTS T1-VSAT - The intelligent earth station

The functional design of the software for NASA's Advanced Communication Technology Satellite (ACTS) T1-VSAT (Very Small Aperture Terminal) is described. The design provides a flexible interface to allow customized control of a satellite network and to provide external processes with access to network capabilities without requiring modification to the network hardware or software. Some of the envisioned features are: automatic number location; dynamic reconfiguration of the number plan tables; security features of call priority, call preemption, and remote verification; automatic reconfiguration of least cost routing tables; circuit availability verification prior to call setup; audio and video conferencing; on demand broadband dial-up service; on demand dial-up broadband broadcast service; and ISDN. A brief review is also given of the ACTS satellite and network, the network management, and the ACTS T1-VSAT earth station.

Manning, John R.↗