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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

The University of Hawaii Institute for Astronomy CCD camera control system

The University of Hawaii Institute for Astronomy CCD Camera Control System consists of a NeXT workstation, a graphical user interface, and a fiber optics communications interface which is connected to a San Diego State University CCD controller. The UH system employs the NeXT-resident Motorola DSP 56001 as a real time hardware controller. The DSP 56001 is interfaced to the Mach-based UNIX of the NeXT workstation by DMA and multithreading. Since the SDSU controller also uses the DPS 56001, the NeXT is used as a development platform for the embedded control software. The fiber optic interface links the two DSP 56001's through their Synchronous Serial Interfaces. The user interface is based on the NeXTStep windowing system. It is easy to use and features real-time display of image data and control over all camera functions. Both Loral and Tektronix 2048 x 2048 CCD's have been driven at full readout speeds, and the system is intended to be capable of simultaneous readout of four such CCD's. The total hardware package is compact enough to be quite portable and has been used on five different telescopes on Mauna Kea. The complete CCD control system can be assembled for a very low cost. The hardware and software of the control system has proven to be quite reliable, well adapted to the needs of astronomers, and extensible to increasingly complicated control requirements.

Jim, K. T. C.↗
NASA NTRS1999

True Concurrent Thermal Engineering Integrating CAD Model Building with Finite Element and Finite Difference Methods

Thermal engineering has long been left out of the concurrent engineering environment dominated by CAD (computer aided design) and FEM (finite element method) software. Current tools attempt to force the thermal design process into an environment primarily created to support structural analysis, which results in inappropriate thermal models. As a result, many thermal engineers either build models "by hand" or use geometric user interfaces that are separate from and have little useful connection, if any, to CAD and FEM systems. This paper describes the development of a new thermal design environment called the Thermal Desktop. This system, while fully integrated into a neutral, low cost CAD system, and which utilizes both FEM and FD methods, does not compromise the needs of the thermal engineer. Rather, the features needed for concurrent thermal analysis are specifically addressed by combining traditional parametric surface based radiation and FD based conduction modeling with CAD and FEM methods. The use of flexible and familiar temperature solvers such as SINDA/FLUINT (Systems Improved Numerical Differencing Analyzer/Fluid Integrator) is retained.

Panczak, Tim↗
NASA NTRS2006

Using Dissimilarity Metrics to Identify Interesting Designs

A computer program helps to blend the power of automated-search software, which is able to generate large numbers of design solutions, with the insight of expert designers, who are able to identify preferred designs but do not have time to examine all the solutions. From among the many automated solutions to a given design problem, the program selects a smaller number of solutions that are worthy of scrutiny by the experts in the sense that they are sufficiently dissimilar from each other. The program makes the selection in an interactive process that involves a sequence of data-mining steps interspersed with visual displays of results of these steps to the experts. At crucial points between steps, the experts provide directives to guide the process. The program uses heuristic search techniques to identify nearly optimal design solutions and uses dissimilarity metrics defined by the experts to characterize the degree to which solutions are interestingly different. The search, data-mining, and visualization features of the program were derived from previously developed risk-management software used to support a risk-centric design methodology

Feather, Martin↗
NASA NTRS2018

Attitude Control System for a Balloon Based Telescope

The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) is an 8-meter interferometer which operates on a high-altitude balloon. BETTII had its first successful engineering flight in June 2017. In this paper we discuss the design of the control system for BETTII, which includes the coarse pointing loop and the estimator controls algorithm (Extended Kalman Filter) implemented in FPGA. We will also discuss the different system modes that we defined in the controls system loop, which are used in different phases of the flight and are activated in order to acquire a target star in the science detector. The pointing loop uses different sensors and actuators in each phase to keep pointing at the desired target. The main sensors aregyroscopes, star cameras, and auxiliary sensors such as high-altitude GPS and magnetometers. The azimuth control is achieved with Compensated Controlled Moment Gyros (CCMG) and a Momentum Dump motor. For the elevation control, high-precision motors are used, which change the elevation of the siderostat mirrors. The combination of these instruments keep the baseline oriented within few arcseconds from the target star.In this paper, we will also present the software architecture relevant to the control system. This includes the description of the two flight computers present on the payload and the different control loops that are executed on them. Similarly, we will explain the importance of synchronization between all the sensors and actuators, which have to be referenced to a single master clock in order to obtain science data.

Vila Hernandez De Lorenzo, Jordi↗
NASA NTRS2017

Behavioral Adaptations of Female Mice on the International Space Station

Adult female mice were sent to the International Space Station (ISS) as part of an early life science mission utilizing NASA's Rodent Habitat. Its primary purpose was to provide further insight into the influence of a microgravity environment on various aspects of mammalian physiology and well-being as part of an ongoing program of research aimed ultimately at understanding and ameliorating the deleterious influences of space on the human body. The present study took advantage of video collected from fixed, in-flight cameras within the habitat itself, to assess behavioral adaptations observed among in-flight mice aboard the ISS and differences in behavior with respect to a control group on the ground. Data collection consisted of several behavioral measures recorded by a trained observer with the assistance of interactive behavior analysis software. Specific behavioral measures included frequencies of conspecific interactionsociability, time spent feeding and conducting hygienic behavior, and relative durations of thigmotactic behavior, which is commonly used as an index of anxiety. Data were used to test tentative hypotheses that such behaviors differ significantly across mice under microgravity versus 1g conditions, and the assumption that the novel experience of microgravity itself may represent an initially anxiogenic stimulus which an animal will eventually acclimate to, perhaps through habituation.

Behavior in space↗
NASA NTRS2017

Behavioral Adaptations of Female Mice on the International Space Station

Adult female mice were sent to the International Space Station (ISS) as part of an early life science mission utilizing NASA's Rodent Habitat. Its primary purpose was to provide further insight into the influence of a microgravity environment on various aspects of mammalian physiology and well-being as part of an ongoing program of research aimed ultimately at understanding and ameliorating the deleterious influences of space on the human body. The present study took advantage of video collected from fixed, in-flight cameras within the habitat itself, to assess behavioral adaptations observed among in-flight mice aboard the ISS and differences in behavior with respect to a control group on the ground. Data collection consisted of several behavioral measures recorded by a trained observer with the assistance of interactive behavior analysis software. Specific behavioral measures included frequencies of conspecific interactionsociability, time spent feeding and conducting hygienic behavior, and relative durations of thigmotactic behavior, which is commonly used as an index of anxiety. Data were used to test tentative hypotheses that such behaviors differ significantly across mice under microgravity versus 1g conditions, and the assumption that the novel experience of microgravity itself may represent an initially anxiogenic stimulus which an animal will eventually acclimate to, perhaps through habituation.

rodent behavior↗
NASA NTRS1987

A measurement-based model of software reliability in a production environment

In this paper, a semi-Markov model is built to describe the software error and recovery process in a large mainframe system. The model is based on low-level error data from the MVS operating system running on an IBM 3081 machine. The semi-Markov model developed provides a quantification of system error characteristics and the interaction between different types of errors. As an example, a detailed model is provided, and an analysis is made of multiple errors, which constitute approximately an 17 percent of all software errors and result in considerable recovery overhead.

Hsueh, M. C.↗
NASA NTRS2005

Hardware in-the-Loop Demonstration of Real-Time Orbit Determination in High Earth Orbits

This paper presents results from a study conducted at Goddard Space Flight Center (GSFC) to assess the real-time orbit determination accuracy of GPS-based navigation in a number of different high Earth orbital regimes. Measurements collected from a GPS receiver (connected to a GPS radio frequency (RF) signal simulator) were processed in a navigation filter in real-time, and resulting errors in the estimated states were assessed. For the most challenging orbit simulated, a 12 hour Molniya orbit with an apogee of approximately 39,000 km, mean total position and velocity errors were approximately 7 meters and 3 mm/s respectively. The study also makes direct comparisons between the results from the above hardware in-the-loop tests and results obtained by processing GPS measurements generated from software simulations. Care was taken to use the same models and assumptions in the generation of both the real-time and software simulated measurements, in order that the real-time data could be used to help validate the assumptions and models used in the software simulations. The study makes use of the unique capabilities of the Formation Flying Test Bed at GSFC, which provides a capability to interface with different GPS receivers and to produce real-time, filtered orbit solutions even when less than four satellites are visible. The result is a powerful tool for assessing onboard navigation performance in a wide range of orbital regimes, and a test-bed for developing software and procedures for use in real spacecraft applications.

Moreau, Michael↗
NASA NTRS1993

Software forecasting as it is really done: A study of JPL software engineers

This paper presents a summary of the results to date of a Jet Propulsion Laboratory internally funded research task to study the costing process and parameters used by internally recognized software cost estimating experts. Protocol Analysis and Markov process modeling were used to capture software engineer's forecasting mental models. While there is significant variation between the mental models that were studied, it was nevertheless possible to identify a core set of cost forecasting activities, and it was also found that the mental models cluster around three forecasting techniques. Further partitioning of the mental models revealed clustering of activities, that is very suggestive of a forecasting lifecycle. The different forecasting methods identified were based on the use of multiple-decomposition steps or multiple forecasting steps. The multiple forecasting steps involved either forecasting software size or an additional effort forecast. Virtually no subject used risk reduction steps in combination. The results of the analysis include: the identification of a core set of well defined costing activities, a proposed software forecasting life cycle, and the identification of several basic software forecasting mental models. The paper concludes with a discussion of the implications of the results for current individual and institutional practices.

Griesel, Martha Ann↗
NASA NTRS1982

GCF Mark IV development

The Mark IV ground communication facility (GCF) as it is implemented to support the network consolidation program is reviewed. Changes in the GCF are made in the area of increased capacity. Common carrier circuits are the medium for data transfer. The message multiplexing in the Mark IV era differs from the Mark III era, in that all multiplexing is done in a GCF computer under GCF software control, which is similar to the multiplexing currently done in the high speed data subsystem.

Mortensen, L. O.↗
NASA NTRS1988

Local area networking: Ames centerwide network

A computer network can benefit the user by making his/her work quicker and easier. A computer network is made up of seven different layers with the lowest being the hardware, the top being the user, and the middle being the software. These layers are discussed.

Price, Edwin↗
NASA NTRS1991

Program For Generating Interactive Displays

Sun/Unix version of Transportable Applications Environment Plus (TAE+) computer program provides integrated, portable software environment for developing and running interactive window, text, and graphical-object-based application software systems. Enables programmer or nonprogrammer to construct easily custom software interface between user and application program and to move resulting interface program and its application program to different computers. Plus viewed as productivity tool for application developers and application end users, who benefit from resultant consistent and well-designed user interface sheltering them from intricacies of computer. Available in form suitable for following six different groups of computers: DEC VAX station and other VMS VAX computers, Macintosh II computers running AUX, Apollo Domain Series 3000, DEC VAX and reduced-instruction-set-computer workstations running Ultrix, Sun 3- and 4-series workstations running Sun OS and IBM RT/PC and PS/2 compute

Costenbader, Jay↗
NASA NTRS1991

Another Program For Generating Interactive Graphics

VAX/Ultrix version of Transportable Applications Environment Plus (TAE+) computer program provides integrated, portable software environment for developing and running interactive window, text, and graphical-object-based application software systems. Enables programmer or nonprogrammer to construct easily custom software interface between user and application program and to move resulting interface program and its application program to different computers. When used throughout company for wide range of applications, makes both application program and computer seem transparent, with noticeable improvements in learning curve. Available in form suitable for following six different groups of computers: DEC VAX station and other VMS VAX computers, Macintosh II computers running AUX, Apollo Domain Series 3000, DEC VAX and reduced-instruction-set-computer workstations running Ultrix, Sun 3- and 4-series workstations running Sun OS and IBM RT/PC's and PS/2 computers running AIX, and HP 9000 S

Costenbader, Jay↗
NASA NTRS1993

A cross-disciplinary response to improve test activities: The corporate memory capitalization in Ariane4 test domain

The Assembly, Integration, Test, and Validation (AIT/AIV) of the Ariane4 Vehicle Equipment Bay was held at Matra Marconi Space (MMS) site of Toulouse for several years. For this activity, incident interpretation necessitates a great deal of different knowledge. When complex faults occur, particularly those appearing during overall control tests, experts of various domains (EGSE, software, on-board equipment) have to join for investigation sessions. Thus, an assistance tool for the identification of faulty equipment will improve the efficiency of diagnosis and the overall productivity of test activities. As a solution, the Aramiihs laboratory proposed considering the opportunity of a knowledge based system intended to assist the tester in diagnosis. This knowledge based system is, in fact, a short-term achievement of a long-term goal which is the capitalization of corporate memory in the Ariane4 test domain. Aramiihs is a research unit where engineers from MMS and researchers from the IRIT-CNRS cooperate on problems concerning new types of man-system interaction.

Vo, Dinh Phuoc↗
NASA NTRS1994

Software reliability studies

There are many software reliability models which try to predict future performance of software based on data generated by the debugging process. Our research has shown that by improving the quality of the data one can greatly improve the predictions. We are working on methodologies which control some of the randomness inherent in the standard data generation processes in order to improve the accuracy of predictions. Our contribution is twofold in that we describe an experimental methodology using a data structure called the debugging graph and apply this methodology to assess the robustness of existing models. The debugging graph is used to analyze the effects of various fault recovery orders on the predictive accuracy of several well-known software reliability algorithms. We found that, along a particular debugging path in the graph, the predictive performance of different models can vary greatly. Similarly, just because a model 'fits' a given path's data well does not guarantee that the model would perform well on a different path. Further we observed bug interactions and noted their potential effects on the predictive process. We saw that not only do different faults fail at different rates, but that those rates can be affected by the particular debugging stage at which the rates are evaluated. Based on our experiment, we conjecture that the accuracy of a reliability prediction is affected by the fault recovery order as well as by fault interaction.

Hoppa, Mary Ann↗
NASA NTRS1994

Image tools for UNIX

This talk features two simple and useful tools for digital image processing in the UNIX environment. They are xv and pbmplus. The xv image viewer which runs under the X window system reads images in a number of different file formats and writes them out in different formats. The view area supports a pop-up control panel. The 'algorithms' menu lets you blur an image. The xv control panel also activates the color editor which displays the image's color map (if one exists). The xv image viewer is available through the internet. The pbmplus package is a set of tools designed to perform image processing from within a UNIX shell. The acronym 'pbm' stands for portable bit map. Like xv, the pbm plus tool can convert images from and to many different file formats. The source code and manual pages for pbmplus are also available through the internet. This software is in the public domain.

Banks, David C.↗
NASA NTRS1996

High speed simulator: A simulator for all seasons

The evolution of a high speed spacecraft simulator (HSS) is discussed from development and operations perspectives. The HSS is a series of simulators capable of modeling the spacecraft and its subsystems at different levels. The HSS was developed for the validation of the Galileo low gain antenna mission's flight software. Due to the successful performance of the HSS in assisting with the flight software validation, additional Galileo validation applications were identified. These applications include the modeling of other onboard data systems, such as the command and data subsystem and the attitude and articulation control subsystem. The HSS architecture, which consists of a number of components, is described and the operational use of the system is outlined.

Patel, K.↗
NASA NTRS1998

Experimental Results and Issues on Equalization for Nonlinear Memory Channel: Pre-Cursor Enhanced Ram-DFE Canceler

This thesis investigates the effects of the High Power Amplifier (HPA) and the filters over a satellite or telemetry channel. The Volterra series expression is presented for the nonlinear channel with memory, and the algorithm is based on the finite-state machine model. A RAM-based algorithm operating on the receiver side, Pre-cursor Enhanced RAM-FSE Canceler (PERC) is developed. A high order modulation scheme , 16-QAM is used for simulation, the results show that PERC provides an efficient and reliable method to transmit data on the bandlimited nonlinear channel. The contribution of PERC algorithm is that it includes both pre-cursors and post-cursors as the RAM address lines, and suggests a new way to make decision on the pre-addresses. Compared with the RAM-DFE structure that only includes post- addresses, the BER versus Eb/NO performance of PERC is substantially enhanced. Experiments are performed for PERC algorithms with different parameters on AWGN channels, and the results are compared and analyzed. The investigation of this thesis includes software simulation and hardware verification. Hardware is setup to collect actual TWT data. Simulation on both the software-generated data and the real-world data are performed. Practical limitations are considered for the hardware collected data. Simulation results verified the reliability of the PERC algorithm. This work was conducted at NMSU in the Center for Space Telemetering and Telecommunications Systems in the Klipsch School of Electrical and Computer Engineering Department.

Yuan, Lu↗