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NASA NTRS1985

Validation of the communications link analysis and simulation system (CLASS)

CLASS (Communication Link Analysis and Simulation System) is a software package developed for NASA to predict the communication and tracking performance of the Tracking and Data Relay Satellite System (TDRSS) services. The methods used to verify CLASS are described. The usefulness of a software tool such as CLASS depends strongly on the reliability and accuracy of the results it produces. For this reason, considerable attention was paid to validation throughout the CLASS development.

Braun, W. R.↗

NASA NTRS1985

Annotated bibliography of Software Engineering Laboratory literature

An annotated bibliography of technical papers, documents, and memorandums produced by or related to the Software Engineering Laboratory is presented. More than 100 publications are summarized. These publications are summarized. These publications cover many areas of software engineering and range from research reports to software documentation. This document has been updated and reorganized substantially since the original version (SEL-82-006, November 1982). All materials are grouped into five general subject areas for easy reference: (1) the software engineering laboratory; (2) software tools; (3) models and measures; (4) technology evaluations; and (5) data collection. An index further classifies these documents by specific topic.

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NASA NTRS1985

Space station data system analysis/architecture study. Task 2: Options development DR-5. Volume 1: Technology options

The second task in the Space Station Data System (SSDS) Analysis/Architecture Study is the development of an information base that will support the conduct of trade studies and provide sufficient data to make key design/programmatic decisions. This volume identifies the preferred options in the technology category and characterizes these options with respect to performance attributes, constraints, cost, and risk. The technology category includes advanced materials, processes, and techniques that can be used to enhance the implementation of SSDS design structures. The specific areas discussed are mass storage, including space and round on-line storage and off-line storage; man/machine interface; data processing hardware, including flight computers and advanced/fault tolerant computer architectures; and software, including data compression algorithms, on-board high level languages, and software tools. Also discussed are artificial intelligence applications and hard-wire communications.

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NASA NTRS1985

Utility of an emulation and simulation computer model for air revitalization system hardware design, development, and test

Efforts to make increasingly use of suitable computer programs in the design of hardware have the potential to reduce expenditures. In this context, NASA has evaluated the benefits provided by software tools through an application to the Environmental Control and Life Support (ECLS) system. The present paper is concerned with the benefits obtained by an employment of simulation tools in the case of the Air Revitalization System (ARS) of a Space Station life support system. Attention is given to the ARS functions and components, a computer program overview, a SAND (solid amine water desorbed) bed model description, a model validation, and details regarding the simulation benefits.

Yanosy, J. L.↗

NASA NTRS1987

The hypercluster: A parallel processing test-bed architecture for computational mechanics applications

The development of numerical methods and software tools for parallel processors can be aided through the use of a hardware test-bed. The test-bed architecture must be flexible enough to support investigations into architecture-algorithm interactions. One way to implement a test-bed is to use a commercial parallel processor. Unfortunately, most commercial parallel processors are fixed in their interconnection and/or processor architecture. In this paper, we describe a modified n cube architecture, called the hypercluster, which is a superset of many other processor and interconnection architectures. The hypercluster is intended to support research into parallel processing of computational fluid and structural mechanics problems which may require a number of different architectural configurations. An example of how a typical partial differential equation solution algorithm maps on to the hypercluster is given.

Blech, Richard A.↗

NASA NTRS1987

Operator function modeling: An approach to cognitive task analysis in supervisory control systems

In a study of models of operators in complex, automated space systems, an operator function model (OFM) methodology was extended to represent cognitive as well as manual operator activities. Development continued on a software tool called OFMdraw, which facilitates construction of an OFM by permitting construction of a heterarchic network of nodes and arcs. Emphasis was placed on development of OFMspert, an expert system designed both to model human operation and to assist real human operators. The system uses a blackboard method of problem solving to make an on-line representation of operator intentions, called ACTIN (actions interpreter).

Mitchell, Christine M.↗

NASA NTRS1987

A generic applications subroutine library for the MPP

A new methodology to increase the utility of the Massively Parallel Processor (MPP) was developed, and is presented as an addition to the current methods of using the MPP. This methodology provides for the development of an MPP side abstraction layer that is callable from any host side high level language. Routines in the abstraction layer have the option of using a powerful software tool for accessing the stager as virtual memory. An additional abstraction layer that allows for remote access to the MPP via DECnet is discussed. This integrated approach to programming the MPP is a valuable tool for the implementation of interactive user driver systems that require the computational capabilities of the MPP as well as a controlled user view. It is expected that this methodology will be used to integrate the MPP into many such systems, and thus promote greater use of the MPP by scientific researchers who are accustomed to user friendly environments.

Gough, Michael L.↗

NASA NTRS1985

KSC Space Station Operations Language (SSOL)

The Space Station Operations Language (SSOL) will serve a large community of diverse users dealing with the integration and checkout of Space Station modules. Kennedy Space Center's plan to achieve Level A specification of the SSOL system, encompassing both its language and its automated support environment, is presented in the format of a briefing. The SSOL concept is a collection of fundamental elements that span languages, operating systems, software development, software tools and several user classes. The approach outlines a thorough process that combines the benefits of rapid prototyping with a coordinated requirements gathering effort, yielding a Level A specification of the SSOL requirements.

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NASA NTRS1987

Space station data management system - A common GSE test interface for systems testing and verification

This paper examines the fundamental problems and goals associated with test, verification, and flight-certification of man-rated distributed data systems. First, a summary of the characteristics of modern computer systems that affect the testing process is provided. Then, verification requirements are expressed in terms of an overall test philosophy for distributed computer systems. This test philosophy stems from previous experience that was gained with centralized systems (Apollo and the Space Shuttle), and deals directly with the new problems that verification of distributed systems may present. Finally, a description of potential hardware and software tools to help solve these problems is provided.

Martinez, Pedro A.↗

NASA NTRS1986

Feasibility study on 8PSK, QPSK, TFM, by using CLASS for Space Station/TDRSS real measured channel

The feasibility of transmitting 500 Mbps data rate through the TDRSS real channel (about 2.5 bits/sec/Hz) for the Space Station application is studied in this paper. The modulation schemes examined are octal phase shift keying, quarternary phase shift keying, and tamed frequency modulation scheme. The software tool used is the Communication Link Analysis and Simulation System. A channel equalizer is shown to be required for such application. Sensitivity results, eye diagrams, and phase trajectory diagrams are presented for discussions.

An, Song H.↗

NASA NTRS1987

Standards for the user interface - Developing a user consensus

The user support environment (USE) which is a set of software tools for a flexible standard interactive user interface to the Space Station systems, platforms, and payloads is described in detail. Included in the USE concept are a user interface language, a run time environment and user interface management system, support tools, and standards for human interaction methods. The goals and challenges of the USE are discussed as well as a methodology based on prototype demonstrations for involving users in the process of validating the USE concepts. By prototyping the key concepts and salient features of the proposed user interface standards, the user's ability to respond is greatly enhanced.

Moe, Karen L.↗

NASA NTRS1987

A new simulation model building process for use in dynamic systems integration research

A framework to build simulation models for aircraft dynamic systems integration is described. The objective of the framework is increased simulation model fidelity and reduced time required to develop and modify these models. The equations of motion for an elastic aircraft and their impact on the framework are discussed in broad terms. A software tool which automatically generates FORTRAN routines for tabular data lookups, the language used to develop a simulation model, and the structures for passing information into a simulation are discussed. A simulation variable nomenclature is presented. The framework has been applied to build an open-loop F/A-18 simulation model. This example model is used to illustrate model reduction issues. Current deficiencies in the framework are identified as areas for future research.

Arbuckle, P. Douglas↗

NASA NTRS1988

Analyzing Solar-Power Options For Spacecraft

Solar Space Power Analysis Code, SOSPAC, developed to examine solar-thermal and photovoltaic power-generation options available for satellite or spacecraft in low orbit around Earth. Is software tool for preliminary analysis of systems and enables engineer to compare areas, weights, and costs of several candidate electric- and thermal-power systems. Configurations studied include photovoltaic arrays and paraboloidal-dish systems to produce electricity only and in various combinations to provide both thermal and electric power. Written in FORTRAN IV.

Selcuk, M. K.↗

NASA NTRS1988

Semi-Markov Unreliability-Range Evaluator

Reconfigurable, fault-tolerant systems modeled. Semi-Markov unreliability-range evaluator (SURE) computer program is software tool for analysis of reliability of reconfigurable, fault-tolerant systems. Based on new method for computing death-state probabilities of semi-Markov model. Computes accurate upper and lower bounds on probability of failure of system. Written in PASCAL.

Butler, Ricky W.↗

NASA NTRS1988

Selected Tether Applications Cost Model

Diverse cost-estimating techniques and data combined into single program. Selected Tether Applications Cost Model (STACOM 1.0) is interactive accounting software tool providing means for combining several independent cost-estimating programs into fully-integrated mathematical model capable of assessing costs, analyzing benefits, providing file-handling utilities, and putting out information in text and graphical forms to screen, printer, or plotter. Program based on Lotus 1-2-3, version 2.0. Developed to provide clear, concise traceability and visibility into methodology and rationale for estimating costs and benefits of operations of Space Station tether deployer system.

Keeley, Michael G.↗

NASA NTRS1987

NASA JSC neural network survey results

A survey of Artificial Neural Systems in support of NASA's (Johnson Space Center) Automatic Perception for Mission Planning and Flight Control Research Program was conducted. Several of the world's leading researchers contributed papers containing their most recent results on artificial neural systems. These papers were broken into categories and descriptive accounts of the results make up a large part of this report. Also included is material on sources of information on artificial neural systems such as books, technical reports, software tools, etc.

Greenwood, Dan↗

NASA NTRS1988

A new gravitational model for the earth from satellite tracking data - GEM-T1

A computation of a terrestrial gravitational field model called the Goddard Earth Model GEM-T1 is discussed and compared to previous models, including the GEM-L2. The software tools were redesigned for the model, allowing for the optimization of the technique of relative data weighting and model estimation used in GEM solutions. The GEM-T1 model provides a simultaneous solution for a gravity model in spherical harmonics complete to degree and order 36, a subset of 66 ocean tidal coefficients for the long-wavelength components of 12 major tides, and 5-day averaged earth rotation and polar motion parameters for the 1980 period on. GEM-T1 was derived from satellite tracking data acquired on 17 different satellites whose inclinations ranged from 15 degrees to polar. A simulation of the TOPEX/POSEIDON orbit using the covariances of the GEM-T1 model was made. Estimated radial error for the simulation was reduced to less than 30 cm rms.

Marsh, J. G.↗

NASA NTRS1989

Simulation Of Satellite Trajectories And Navigation

Orbit Analysis and Simulation Software, OASIS, is software system developed for covariance and simulation analyses of problems involving Earth satellites, especially Global Positioning System (GPS). Provides flexible, versatile, and efficient software tool for analysis of accuracy in Earth-satellite navigation and GPS-based geodetic studies.

Wu, Sien-Chong↗