Software-Implementation Plan
Top-down implementation plan provides a methodology for solving problems in or aiding software engineering design.
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Top-down implementation plan provides a methodology for solving problems in or aiding software engineering design.
A preprocessing system, designed and constructed for use with the University of Illinois sodium lidar system, was developed to increase the altitude resolution and range of the lidar system and also to decrease the processing burden of the main lidar computer. The preprocessing system hardware and the software required to implement the system are described. Some preliminary results of an airborne sodium lidar experiment conducted with the preprocessing system installed in the sodium lidar are presented.
A sensor failure detection, isolation, and accommodation algorithm was developed which incorporates analytic sensor redundancy through software. This algorithm was implemented in a high level language on a microprocessor based controls computer. Parallel processing and state-of-the-art 16-bit microprocessors are used along with efficient programming practices to achieve real-time operation.
Elastic-plastic analytic capabilities were incorporated into the NASTRAN program. The present implementation includes a general rigid format and additional bulk data cards as well as to two new modules. The modules are specialized to include only perfect plasticity of the CTRMEN and CROD elements but can easily be expanded to include other plasticity theories and elements. The practical problem of an elastic-plastic analysis of a ship's bracket connection is demonstrated and compared to an equivalent analysis using Grumman's PLANS program. The present work demonstrates the feasibility of incorporating general elastic-plastic capabilities into NASTRAN.
The pilot-machine interface with aircraft automation to increase the safety and utility of single-pilot IFR (instrument flight rules) operations is addressed. An automatic terminal approach system (ATAS), that uses stored instrument approach data to automatically tune aircraft radios and control the aircraft autopilot, was conceived as a means of improving this critical interface. The ATAS automatically flies instrument approach procedures, including the missed approach, and provides for easy pilot interaction to accommodate air traffic control radar vectors and altitude assignments. A research prototype of an ATAS was developed to the extent necessary for a simulation implementation and piloted evaluation. The development of the ATAS concept and the software algorithms is described.
A brief description of the Model of the World Economy implemented at the Institute for Economic Analysis is presented, together with our experience in converting the software to vector code. For each time period, the model is reduced to a linear system of over 2000 variables. The matrix of coefficients has a bordered block diagonal structure, and we show how some of the matrix operations can be carried out on all diagonal blocks at once.
The use and implementation of Ada (a trade mark of the US Dept. of Defense) in distributed environments in which the hardware are assumed to be unreliable were investigated. The possibility that a distributed system is programmed entirely in Ada so that the individual tasks of the system are unconcerned with which processors they are executing on and failures occurring in the underlying hardware were examined.
The Software Implemented Fault Tolerance SIFT specifications consist primarily of constraints on the schedule table and descriptions of the changes each routine makes to the global variables. The proof proceeds by proving that each routine is consistent with its specification. Each of these proofs is separate from the others and the order of the proofs is unimportant. A routine is proved by generating a set of verification conditions from the PASCAL code and the SPECIAL specifications. Each verification condition is a set of assertions derived from a particular path in the routine. A verification condition (VC) is generated for each possible path through the routine.
The motivation to use phase coded observations for the stratosphere-troposphere region is discussed. Previous work using hardware correlators to decode the received signal is referred. An alternative technique using software to decode the signal samples is described, and results of the implementation are presented.
An overview of the basic space station infrastructure is presented. A strong case is made for the evolution of the station using the basic Space Transportation System (STS) to achieve a smooth transition and cost effective implementation. The integrated logistics support (ILS) element of the overall station infrastructure is investigated. The need for an orbital transport system capability that is the key to servicing and spacecraft positioning scenarios and associated mission needs is examined. Communication is also an extremely important element and the basic issue of station autonomy versus ground support effects the system and subsystem architecture.
The requirements implementation strategy for first level development of the Integrated Programs for Aerospace Vehicle Design (IPAD) computing system is presented. The capabilities of first level IPAD are sufficient to demonstrated management of engineering data on two computers (CDC CYBER 170/720 and DEC VAX 11/780 computers) using the IPAD system in a distributed network environment.
The use and implementation of Ada in distributed environments in which reliability is the primary concern is investigated. Emphasis is placed on the possibility that a distributed system may be programmed entirely in ADA so that the individual tasks of the system are unconcerned with which processors they are executing on, and that failures may occur in the software or underlying hardware. The primary activities are: (1) Continued development and testing of our fault-tolerant Ada testbed; (2) consideration of desirable language changes to allow Ada to provide useful semantics for failure; (3) analysis of the inadequacies of existing software fault tolerance strategies.
A 12.2 meter diameter X-Y mount antenna was reconditioned for use by the crustal dynamic project as a fixed base station. System capabilities and characteristics and key performance parameters for subsystems are presented. The implementation is completed.
The space telescope management information system development effort is a guideline for discussing effective organizational solutions used in implementing DBMS software. Focus is on the importance of strategic planning. The value of constructing an information system architecture to conform to the organization's managerial needs, the need for a senior decision maker, dealing with shifting user requirements, and the establishment of a reliable working relationship with the DBMS vendor are examined. Requirements for a schedule to demonstrate progress against a defined timeline and the importance of continued monitoring for production software control, production data control, and software enhancements are also discussed.
Program development for a Software Implemented Fault Tolerant (SIFT) computer system is accomplished in the NASA LaRC AIRLAB facility using a DEC VAX-11 to interface with eight Bendix BDX 930 flight control processors. The interface software which provides this SIFT program development capability was developed by AIRLAB personnel. This technical memorandum describes the application and design of this software in detail, and is intended to assist both the user in performance of SIFT research and the systems programmer responsible for maintaining and/or upgrading the SIFT programming environment.
A progress report is presented on a program to upgrade the existing NASA Deep Space Network in terms of a redesigned computer-controlled data acquisition system for channelling tracking, telemetry, and command data between a California-based control center and three signal processing centers in Australia, California, and Spain. The methodology for the improvements is oriented towards single subsystem development with consideration for a multi-system and multi-subsystem network of operational software. Details of the existing hardware configurations and data transmission links are provided. The program methodology includes data flow design, interface design and coordination, incremental capability availability, increased inter-subsystem developmental synthesis and testing, system and network level synthesis and testing, and system verification and validation. The software has been implemented thus far to a 65 percent completion level, and the methodology being used to effect the changes, which will permit enhanced tracking and communication with spacecraft, has been concluded to feature effective techniques.
Discussed in this paper are some of the problems associated with implementing microcomputer-based power system autonomy on spacecraft flight projects, as well as limitations derived from prior development programs. A new approach is given for developing the autonomy architecture, and an architecture concept, based on that approach, is described.
A sensor failure detection, isolation, and accommodation algorithm was developed which incorporates analytic sensor redundancy through software. This algorithm was implemented in a high level language on a microprocessor based controls computer. Parallel processing and state-of-the-art 16-bit microprocessors are used along with efficient programming practices to achieve real-time operation. Previously announced in STAR as N84-13140