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At least 307 records · Page 17

All sources NASA NTRS DOE OSTI

NASA NTRS1982

Shuttle automatic landing system

The Shuttle automatic landing system design requirements are discussed, the approach and landing flight phase is described, and the hardware and software subsystems are functionally described. Emphasis is placed on the complexity, flexibility, and criticality of the software function. The software structure, critical computational problems, and verification process as a subsystem are discussed. Finally, the hardware/software verification activities required before flight test of the autoland system are described, along with the results from two flight tests and the planned system certification to the operational flight boundaries.

Tsikalas, G.↗

NASA NTRS1986

The design and application of a Transportable Inference Engine (TIE1)

A Transportable Inference Engine (TIE1) system has been developed by the author as part of the Interactive Experimenter Planning System (IEPS) task which is involved with developing expert systems in support of the Spacecraft Control Programs Branch at Goddard Space Flight Center in Greenbelt, Maryland. Unlike traditional inference engines, TIE1 is written in the C programming language. In the TIE1 system, knowledge is represented by a hierarchical network of objects which have rule frames. The TIE1 search algorithm uses a set of strategies, including backward chaining, to obtain the values of goals. The application of TIE1 to a spacecraft scheduling problem is described. This application involves the development of a strategies interpreter which uses TIE1 to do constraint checking.

Mclean, David R.↗

NASA NTRS1986

The design and application of a Transportable Inference Engine (TIE1)

Mclean, David R.↗

NASA NTRS1999

Spacecraft Environments Interactive: Space Radiation and Its Effects on Electronic System

The natural space environment is characterized by complex and subtle phenomena hostile to spacecraft. Effects of these phenomena impact spacecraft design, development, and operation. Space systems become increasingly susceptible to the space environment as use of composite materials and smaller, faster electronics increases. This trend makes an understanding of space radiation and its effects on electronic systems essential to accomplish overall mission objectives, especially in the current climate of smaller/better/cheaper faster. This primer outlines the radiation environments encountered in space, discusses regions and types of radiation, applies the information to effects that these environments have on electronic systems, addresses design guidelines and system reliability, and stresses the importance of early involvement of radiation specialists in mission planning, system design, and design review (part-by-part verification).

Howard, J. W., Jr.↗

NASA NTRS2010

360-Degree Visual Detection and Target Tracking on an Autonomous Surface Vehicle

This paper describes perception and planning systems of an autonomous sea surface vehicle (ASV) whose goal is to detect and track other vessels at medium to long ranges and execute responses to determine whether the vessel is adversarial. The Jet Propulsion Laboratory (JPL) has developed a tightly integrated system called CARACaS (Control Architecture for Robotic Agent Command and Sensing) that blends the sensing, planning, and behavior autonomy necessary for such missions. Two patrol scenarios are addressed here: one in which the ASV patrols a large harbor region and checks for vessels near a fixed asset on each pass and one in which the ASV circles a fixed asset and intercepts approaching vessels. This paper focuses on the ASV's central perception and situation awareness system, dubbed Surface Autonomous Visual Analysis and Tracking (SAVAnT), which receives images from an omnidirectional camera head, identifies objects of interest in these images, and probabilistically tracks the objects' presence over time, even as they may exist outside of the vehicle's sensor range. The integrated CARACaS/SAVAnT system has been implemented on U.S. Navy experimental ASVs and tested in on-water field demonstrations.

ASV (AUTONOMOUS SEA SURFACE VEHICLE)↗

NASA NTRS1974

Modeling and analysis of power processing systems: Feasibility investigation and formulation of a methodology

A review is given of future power processing systems planned for the next 20 years, and the state-of-the-art of power processing design modeling and analysis techniques used to optimize power processing systems. A methodology of modeling and analysis of power processing equipment and systems has been formulated to fulfill future tradeoff studies and optimization requirements. Computer techniques were applied to simulate power processor performance and to optimize the design of power processing equipment. A program plan to systematically develop and apply the tools for power processing systems modeling and analysis is presented so that meaningful results can be obtained each year to aid the power processing system engineer and power processing equipment circuit designers in their conceptual and detail design and analysis tasks.

Biess, J. J.↗

NASA NTRS1981

OSTA/ADS standards development process

A phased approach to data systems standards was developed. The standards survey, user requirements, methodology survey, and evaluation criteria were completed. Remaining to be done are data system planning interim standards, a concept for implementation of a core applications data service, a data systems policy definition, and full capability data services definition.

Walton, B.↗

NASA NTRS2015

Precision Time Protocol-Based Trilateration for Planetary Navigation

Progeny Systems Corporation has developed a high-fidelity, field-scalable, non-Global Positioning System (GPS) navigation system that offers precision localization over communications channels. The system is bidirectional, providing position information to both base and mobile units. It is the first-ever wireless use of the Institute of Electrical and Electronics Engineers (IEEE) Precision Time Protocol (PTP) in a bidirectional trilateration navigation system. The innovation provides a precise and reliable navigation capability to support traverse-path planning systems and other mapping applications, and it establishes a core infrastructure for long-term lunar and planetary occupation. Mature technologies are integrated to provide navigation capability and to support data and voice communications on the same network. On Earth, the innovation is particularly well suited for use in unmanned aerial vehicles (UAVs), as it offers a non-GPS precision navigation and location service for use in GPS-denied environments. Its bidirectional capability provides real-time location data to the UAV operator and to the UAV. This approach optimizes assisted GPS techniques and can be used to determine the presence of GPS degradation, spoofing, or jamming.

Murdock, Ron↗

NASA NTRS1982

Baseband-processed SS-TDMA communication system architecture and design concepts

The architecture and system design for a commercial satellite communications system planned for the 1990's was developed by Motorola for NASA's Lewis Research Center. The system provides data communications between individual users via trunking and customer premises service terminals utilizing a central switching satellite operating in a time-division multiple-access (TDMA) mode. The major elements of the design incorporating baseband processing include: demand-assigned multiple access reservation protocol, spectral utilization, system synchronization, modulation technique and forward error control implementation. Motorola's baseband processor design, which is being proven in a proof-of-concept advanced technology development, will perform data regeneration and message routing for individual users on-board the spacecraft.

Attwood, S.↗

NASA NTRS1995

Proceedings of the Fourth International Mobile Satellite Conference (IMSC 1995)

The theme to the 1995 International Mobile Satellite Conference was 'Mobile Satcom Comes of Age'. The sessions included Modulation, Coding, and Multiple Access; Hybrid Networks - 1; Spacecraft Technology; propagation; Applications and Experiments - 1; Advanced System Concepts and Analysis; Aeronautical Mobile Satellite Communications; Mobile Terminal Antennas; Mobile Terminal Technology; Current and Planned Systems; Direct Broadcast Satellite; The Use of CDMA for LEO and ICO Mobile Satellite Systems; Hybrid Networks - 2; and Applications and Experiments - 2.

J R Rigley↗

NASA NTRS1992

Assessment of avionics technology in European aerospace organizations

This report provides a summary of the observations and recommendations made by a technical panel formed by the National Aeronautics and Space Administration (NASA). The panel, comprising prominent experts in the avionics field, was tasked to visit various organizations in Europe to assess the level of technology planned for use in manufactured civil avionics in the future. The primary purpose of the study was to assess avionics systems planned for implementation or already employed on civil aircraft and to evaluate future research, development, and engineering (RD&E) programs, address avionic systems and aircraft programs. The ultimate goal is to ensure that the technology addressed by NASa programs is commensurate with the needs of the aerospace industry at an international level. The panel focused on specific technologies, including guidance and control systems, advanced cockpit displays, sensors and data networks, and fly-by-wire/fly-by-light systems. However, discussions the panel had with the European organizations were not limited to these topics.

Martinec, D. A.↗

NASA NTRS1994

Why Real-World Planning is Difficult

This paper describes several major obstacles to the fielding of planning systems.

procedural-reasoning planning and decision support↗

NASA NTRS1988

Explanation production by expert planners

Although the explanation capability of expert systems is usually listed as one of the distinguishing characteristics of these systems, the explanation facilities of most existing systems are quite primitive. Computer generated explanations are typically produced from canned text or by direct translation of the knowledge structures. Explanations produced in this manner bear little resemblance to those produced by humans for similar tasks. The focus of our research in explanation is the production of justifications for decisions by expert planning systems. An analysis of justifications written by people for planning tasks has been taken as the starting point. The purpose of this analysis is two-fold. First, analysis of the information content of the justifications will provide a basis for deciding what knowledge must be represented if human-like justifications are to be produced. Second, an analysis of the textual organization of the justifications will be used in the development of a mechanism for selecting and organizing the knowledge to be included in a computer-produced explanation. This paper describes a preliminary analysis done of justifications written by people for a planning task. It is clear that these justifications differ significantly from those that would be produced by an expert system by tracing the firing of production rules. The results from the text analysis have been used to develop an augmented phrase structured grammar (APSG) describing the organization of the justifications. The grammar was designed to provide a computationally feasible method for determining textual organization that will allow the necessary information to be communicated in a cohesive manner.

Bridges, Susan↗

NASA NTRS1992

Mathematical Modeling Of The Terrain Around A Robot

In conceptual system for modeling of terrain around autonomous mobile robot, representation of terrain used for control separated from representation provided by sensors. Concept takes motion-planning system out from under constraints imposed by discrete spatial intervals of square terrain grid(s). Separation allows sensing and motion-controlling systems to operate asynchronously; facilitating integration of new map and sensor data into planning of motions.

Slack, Marc G.↗

NASA NTRS1971

Broadcast control of air traffic

Concepts of increased pilot participation in air traffic control are presented. The design of an air traffic control system for pilot usage is considered. The operating and safety benefits of LF/VLF approaches in comparison to current nonprecision approach procedures and systems are discussed. With a good national system plan, flight testing and validation, and the use of local differential, or general diurnal, corrections, the LF/VLF system would provide service superior to that presently available.

Litchford, G. B.↗

NASA NTRS1987

Recovering from execution errors in SIPE

In real-world domains (e.g., a mobile robot environment), things do not always proceed as planned, so it is important to develop better execution-monitoring techniques and replanning capabilities. These capabilities in the SIPE planning system are described. The motivation behind SIPE is to place enough limitations on the representation so that planning can be done efficiently, while retaining sufficient power to still be useful. This work assumes that new information given to the execution monitor is in the form of predicates, thus avoiding the difficult problem of how to generate these predicates from information provided by sensors. The replanning module presented here takes advantage of the rich structure of SIPE plans and is intimately connected with the planner, which can be called as a subroutine. This allows the use of SIPE's capabilities to determine efficiently how unexpected events affect the plan being executed and, in many cases, to retain most of the original plan by making changes in it to avoid problems caused by these unexpected events. SIPE is also capable of shortening the original plan when serendipitous events occur. A general set of replanning actions is presented along with a general replanning capability that has been implemented by using these actions.

Wilkins, D. E.↗

NASA NTRS1991

Operator-assisted planning and execution of proximity operations subject to operational constraints

Future multi-vehicle operations will involve multiple scenarios that will require a planning tool for the rapid, interactive creation of fuel-efficient trajectories. The planning process must deal with higher-order, non-linear processes involving dynamics that are often counter-intuitive. The optimization of resulting trajectories can be difficult to envision. An interaction proximity operations planning system is being developed to provide the operator with easily interpreted visual feedback of trajectories and constraints. This system is hosted on an IRIS 4D graphics platform and utilizes the Clohessy-Wiltshire equations. An inverse dynamics algorithm is used to remove non-linearities while the trajectory maneuvers are decoupled and separated in a geometric spreadsheet. The operator has direct control of the position and time of trajectory waypoints to achieve the desired end conditions. Graphics provide the operator with visualization of satisfying operational constraints such as structural clearance, plume impingement, approach velocity limits, and arrival or departure corridors. Primer vector theory is combined with graphical presentation to improve operator understanding of suggested automated system solutions and to allow the operator to review, edit, or provide corrective action to the trajectory plan.

Grunwald, Arthur J.↗

NASA NTRS2008

Application of Space Environmental Observations to Spacecraft Pre-Launch Engineering and Spacecraft Operations

This presentation focuses on the effects of the space environment on spacecraft systems and applying this knowledge to spacecraft pre-launch engineering and operations. Particle radiation, neutral gas particles, ultraviolet and x-rays, as well as micrometeoroids and orbital debris in the space environment have various effects on spacecraft systems, including degradation of microelectronic and optical components, physical damage, orbital decay, biasing of instrument readings, and system shutdowns. Space climate and weather must be considered during the mission life cycle (mission concept, mission planning, systems design, and launch and operations) to minimize and manage risk to both the spacecraft and its systems. A space environment model for use in the mission life cycle is presented.

Barth, Janet L.↗