Information Science

Software Framework for Peer Data-Management Services

Object Oriented Data Technology (OODT) is a software framework for creating a Web-based system for exchange of scientific data that are stored in diverse formats on computers at different sites under the management of scientific peers. OODT software consists of a set of cooperating, distributed peer components that provide distributed peer-to-peer (P2P) services that enable one peer to search and retrieve data managed by another peer. In effect, computers running OODT software at different locations become parts of an integrated data-management system.

Posted in: Information Sciences, Briefs

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C Namelist Facility

C Namelist Facility (CNL) is a package of software that supports the development of data-driven programs that utilize relatively free-form input files (e.g., text files) to control complex operations. The only comparable prior namelist facility is built into Fortran and does not support arrays or records. Newer computing languages, including C and Pascal, do not include built-in namelist facilities. A namelist facility enables a program to utilize relatively free-form input files that contain assignment statements that give values to variables. Variables to which values are not assigned in input files remain unchanged; therefore, it becomes possible to have default values set by static or dynamic initialization of values prior to namelist input and updating of values is optional. Because it is not required to include values of variables in namelist input files, new parameters can be added to evolving programs without rendering old namelist input files obsolete — provided that the new parameters have useful default values. It should be possible to execute CNL in any operating system that supports the ANSI C programming language. It has been executed in several variants of Unix and in VxWorks.

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Initialized Fractional Calculus

Initialization functions are essential to a revised formulation suitable for engineering and scientific applications. The fractional calculus (which admits of integrals and derivatives of non-integer order) dates back almost to the origin of the better-known ordinary (integer-order) calculus, but thus far has been treated more as a mathematical curiosity than as a scientific and engineering tool. Increasingly many physical processes are found to be best described using fractional differential equations. These processes include: viscoelasticity, rheology, electrochemistry, fractal processes, and many diffusion processes. The application of the fractional calculus to scientific and engineering problems has been inhibited by difficulties that arise from the basic definitions given heretofore for integrals and derivatives of arbitrary order. These difficulties are associated with the initialization problem, which is explained below.

Posted in: Information Sciences, Briefs, TSP

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Remote Agent as Applied to the Deep Space 1 Spacecraft

A report presents updated information about the Remote Agent — a reusable artificial-intelligence software system that was described in “A Remote Agent Prototype for Spacecraft Autonomy” (NPO-19992), NASA Tech Briefs, Vol. 21, No. 3 (March 1997), page 106. This system was conceived to enable spacecraft to operate robustly with minimal human supervision, even in the face of hardware failures or unexpected events. It also is expected to offer similar benefits for communication networks, chemical plants, and other complex systems on Earth.

Posted in: Information Sciences, Briefs, TSP

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Goal-Based Fault Tolerance for Spacecraft Systems

A report discusses the concept of goal-based fault tolerance as implemented in NASA’s Mission Data System (MDS), which is a developmental architecture for unified flight, test, and ground software that is intended to be adaptable to a variety of next-generation deep-space missions. In goal-based fault tolerance, unlike in prior approaches to fault tolerance, it is not assumed that faults that necessitate deviations from prescribed sequences of commands will occur infrequently; instead, it is assumed that unpredictable conditions, including faults, can arise at any time, and fault tolerance is incorporated as an intrinsic feature of every aspect of system design in a unified approach to ensuring robust system behavior.

Posted in: Information Sciences, Briefs, TSP

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Quantum Superluminal Transmission of Random Messages

Messages that would not convey information could be useful for deception. In a proposed communication scheme, quantum entanglement and quantum nonlocality would be utilized to effect instantaneous transmission of randomly chosen messages to remote locations. Although the messages would not convey any information, they might nevertheless be of some value under circumstances in which deception and secrecy are of more importance than are the specific contents of the messages.

Posted in: Information Sciences, Briefs, TSP

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Maximum-Likelihood Scheme for Tracking an Optical Source

Subpixel resolution should be possible, even in a high-disturbance environment. A fine-pointing scheme that involves correlation of images and maximum-likelihood estimation has been proposed to enable tracking of optical sources. This scheme is intended for implementation in the pointing-control system of an imaging instrument (e.g., a telescope equipped with an image detector) to provide a capability for highly stable and accurate pointing to a specific area within a moving target, even under conditions that ordinarily give rise to pointing jitters. Such conditions include motion of the target relative to the instrument, instability of the platform that supports the instrument-aiming mechanism, and turbulence in the atmosphere or other optical medium. In the original intended application, the scheme would be implemented in a ground station for tracking a laser that would be part of an optical communication aboard a distant spacecraft. Other potential applications include stabilization of images for video cameras and precise pointing of lasers in military, industrial, and surgical settings. This scheme is expected to make it possible to achieve subpixel resolution in a high-disturbance environment.

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