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At least 865 records · Page 48

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NASA NTRS1991

Digital image profilers for detecting faint sources which have bright companions, phase 2

A breadboard image profiling system developed for the first phase of this project demonstrated the potential for detecting extremely faint optical sources in the presence of light companions. Experimental data derived from laboratory testing of the device supports the theory that image profilers of this type may approach the theoretical limit imposed by photon statistics. The objective of Phase 2 of this program is the development of a ground-based multichannel image profiling system capable of detecting faint stellar objects slightly displaced from brighter stars. We have finalized the multichannel image profiling system and attempted three field tests.

Morris, Elena↗

NASA NTRS1992

Antecedent precipitation index determined from CST estimates of rainfall

This paper deals with an experimental calculation of a satellite-based antecedent precipitation index (API). The index is also derived from daily rain images produced from infrared images using an improved version of GSFC's Convective/Stratiform Technique (CST). API is a measure of soil moisture, and is based on the notion that the amount of moisture in the soil at a given time is related to precipitation at earlier times. Four different CST programs as well as the Geostationary Operational Enviroment Satellite (GOES) Precipitation Index developed by Arkin in 1979 are compared to experimental results, for the Mississippi Valley during the month of July. Rain images are shown for the best CST code and the ARK program. Comparisons are made as to the accuracy and detail of the results for the two codes. This project demonstrates the feasibility of running the CST on a synoptic scale. The Mississippi Valley case is well suited for testing the feasibility of monitoring soil moisture by means of CST. Preliminary comparisons of CST and ARK indicate significant differences in estimates of rain amount and distribution.

Martin, David W.↗

NASA NTRS1988

Mars oxygen production system design

This report summarizes the design and construction of the Mars oxygen demonstration project. The basic hardware required to produce oxygen from simulated Mars atmosphere has been assembled and tested. Some design problems still remain with the sample collection and storage system. In addition, design and development of computer data acquisition and control instrumentation is continuing.

Source record↗

NASA NTRS1993

Research in cosmic and gamma ray astrophysics: Cosmic physics portion

Research in particle astrophysics at the Space Radiation Laboratory (SRL) of the California Institute of Technology is supported under NASA Grant NAGW-1919. A three-year proposal for continuation of support was submitted a year ago and put into effect 1 October 1992. This report is the combined progress report and continuation application called for under the Federal Demonstration Project. Gamma-ray Astrophysics at SRL is separately supported under NAGW-1919 and will be separately summarized and proposed. This report will document progress and plans for our particle spectroscopy activities and for related data analysis, calibration, and community service activities. A bibliography and a budget will be attached as appendices. The Caltech SRL research program includes a heavy emphasis on elemental and isotopic spectroscopy of energetic particles in the cosmic radiation; in solar, interplanetary, and anomalous 'cosmic' radiation; and in planetary magnetospheres as discussed.

Stone, Edward C.↗

NASA NTRS1993

Colorimetric qualification of shear sensitive liquid crystal coatings

The work that has been done to date on the Shear Sensitive Liquid Crystal Project demonstrated that cholesteric liquid crystal coatings respond to both the direction and magnitude of a shearing force. The response of the coating is to selectively scatter incident white light into a spectrum of colors. Discernible color changes at a fixed angle of observation and illumination are the result of an applied shear stress. The intention was to be able to convert these observable color patterns from a flow visualization technique into a quantitative tool. One of the earlier intentions was to be able to use liquid crystals in dynamic flow fields. This was assumed possible because liquid crystals had made it possible to visualize transients in surface shear forces. Although the transients were visualized by color changes to an order one micro second, the time response of a coating to align to a shearing force is dependent on the magnitude of the change between its initial and final states. Unfortunately, the response is not instantaneous. It is for this reason any future attempt at quantifying the magnitude and directions of a shearing force are limited to surface shear stress vector fields in three dimensional steady state flows. This limitation does not significantly detract from the utility of liquid crystal coatings. The measurement of skin friction in the study of transition on wings, prediction of drag forces, performance assessment, and the investigation of boundary layer behavior is of great importance in aerodynamics. There exist numerous examples of techniques for the measurement of surface shear stress. Most techniques require arduous calibrations and necessitate extensive preparation of the receiving surfaces. However, the main draw back of instruments such as Preston tubes, hot films, buried wire gages, and floating element balances is that they only provide a point measurement. The advantages of capturing global shear data would be appreciable when compared with conventional point measurement sensors. It has yet to be determined if a repeatable correlation exists between the measured color of a liquid crystal coating and the magnitude/directional components of a shear vector imposed onto it.

Muratore, Joseph J., Jr.↗

NASA NTRS1990

Energetic neutral atoms: Imaging the magnetospheric ring current

Magnetospheric imaging is a new discipline whose goal is to make pictures of the energetic particle populations trapped in the magnetic field of Earth (or any other planet). This project demonstrated the technical feasibility and scientific validity of magnetospheric imaging using energetic neutral atoms (ENA) with the publication and quantitative analysis of the first ENA images ever obtained from space. ENA's are produced when singly-charged energetic (approximately 100 keV) trapped ions make an atomic collision with the neutral hydrogen atoms which boil of the top of the Earth's atmosphere. These hydrogen atoms suffuse the entire trapping volume of the magnetosphere. The energetic ion steals the electron from the atmospheric hydrogen, so the energetic ion is transformed into an energetic neutral atom with a velocity of several thousands of kilometers/second. Moreover, the new-born ENA preserves the velocity that the trapped ion had at the time of the collision. Consequently, any population of energetic ions emits ENA's.

Roelof, Edmond C.↗

NASA NTRS1994

Design of a wheeled articulating land rover

The WALRUS is a wheeled articulating land rover that will provide Ames Research Center with a reliable, autonomous vehicle for demonstrating and evaluating advanced technologies. The vehicle is one component of the Ames Research Center's on-going Human Exploration Demonstration Project. Ames Research Center requested a system capable of traversing a broad spectrum of surface types and obstacles. In addition, this vehicle must have an autonomous navigation and control system on board and its own source of power. The resulting design is a rover that articulates in two planes of motion to allow for increased mobility and stability. The rover is driven by six conical shaped aluminum wheels, each with an independent, internally coupled motor. Mounted on the rover are two housings and a removable remote control system. In the housings, the motor controller board, tilt sensor, navigation circuitry, and QED board are mounted. Finally, the rover's motors and electronics are powered by thirty C-cell rechargeable batteries, which are located in the rover wheels and recharged by a specially designed battery charger.

Stauffer, Larry↗

NASA NTRS1994

An initial investigation into methods of computing transonic aerodynamic sensitivity coefficients

The primary accomplishments of the project are as follows: (1) Using the transonic small perturbation equation as a flowfield model, the project demonstrated that the quasi-analytical method could be used to obtain aerodynamic sensitivity coefficients for airfoils at subsonic, transonic, and supersonic conditions for design variables such as Mach number, airfoil thickness, maximum camber, angle of attack, and location of maximum camber. It was established that the quasi-analytical approach was an accurate method for obtaining aerodynamic sensitivity derivatives for airfoils at transonic conditions and usually more efficient than the finite difference approach. (2) The usage of symbolic manipulation software to determine the appropriate expressions and computer coding associated with the quasi-analytical method for sensitivity derivatives was investigated. Using the three dimensional fully conservative full potential flowfield model, it was determined that symbolic manipulation along with a chain rule approach was extremely useful in developing a combined flowfield and quasi-analytical sensitivity derivative code capable of considering a large number of realistic design variables. (3) Using the three dimensional fully conservative full potential flowfield model, the quasi-analytical method was applied to swept wings (i.e. three dimensional) at transonic flow conditions. (4) The incremental iterative technique has been applied to the three dimensional transonic nonlinear small perturbation flowfield formulation, an equivalent plate deflection model, and the associated aerodynamic and structural discipline sensitivity equations; and coupled aeroelastic results for an aspect ratio three wing in transonic flow have been obtained.

Carlson, Leland A.↗

NASA NTRS1994

The Buffer Diagnostic Prototype: A fault isolation application using CLIPS

This paper describes problem domain characteristics and development experiences from using CLIPS 6.0 in a proof-of-concept troubleshooting application called the Buffer Diagnostic Prototype. The problem domain is a large digital communications subsystems called the real-time network (RTN), which was designed to upgrade the launch processing system used for shuttle support at KSC. The RTN enables up to 255 computers to share 50,000 data points with millisecond response times. The RTN's extensive built-in test capability but lack of any automatic fault isolation capability presents a unique opportunity for a diagnostic expert system application. The Buffer Diagnostic Prototype addresses RTN diagnosis with a multiple strategy approach. A novel technique called 'faulty causality' employs inexact qualitative models to process test results. Experimental knowledge provides a capability to recognize symptom-fault associations. The implementation utilizes rule-based and procedural programming techniques, including a goal-directed control structure and simple text-based generic user interface that may be reusable for other rapid prototyping applications. Although limited in scope, this project demonstrates a diagnostic approach that may be adapted to troubleshoot a broad range of equipment.

Porter, Ken↗

NASA NTRS1995

Probabilistic risk assessment of the Space Shuttle. Phase 3: A study of the potential of losing the vehicle during nominal operation. Volume 5: Auxiliary shuttle risk analyses

Volume 5 is Appendix C, Auxiliary Shuttle Risk Analyses, and contains the following reports: Probabilistic Risk Assessment of Space Shuttle Phase 1 - Space Shuttle Catastrophic Failure Frequency Final Report; Risk Analysis Applied to the Space Shuttle Main Engine - Demonstration Project for the Main Combustion Chamber Risk Assessment; An Investigation of the Risk Implications of Space Shuttle Solid Rocket Booster Chamber Pressure Excursions; Safety of the Thermal Protection System of the Space Shuttle Orbiter - Quantitative Analysis and Organizational Factors; Space Shuttle Main Propulsion Pressurization System Probabilistic Risk Assessment, Final Report; and Space Shuttle Probabilistic Risk Assessment Proof-of-Concept Study - Auxiliary Power Unit and Hydraulic Power Unit Analysis Report.

Fragola, Joseph R.↗

NASA NTRS1995

Use of agents to implement an integrated computing environment

Integrated Product and Process Development (IPPD) embodies the simultaneous application to both system and quality engineering methods throughout an iterative design process. The use of IPPD results in the time-conscious, cost-saving development of engineering systems. To implement IPPD, a Decision-Based Design perspective is encapsulated in an approach that focuses on the role of the human designer in product development. The approach has two parts and is outlined in this paper. First, an architecture, called DREAMS, is being developed that facilitates design from a decision-based perspective. Second, a supporting computing infrastructure, called IMAGE, is being designed. Agents are used to implement the overall infrastructure on the computer. Successful agent utilization requires that they be made of three components: the resource, the model, and the wrap. Current work is focused on the development of generalized agent schemes and associated demonstration projects. When in place, the technology independent computing infrastructure will aid the designer in systematically generating knowledge used to facilitate decision-making.

Hale, Mark A.↗

NASA NTRS1995

Introduction to Penelope

A formal program verification is a (mathematical) proof that a program executed according to its intended model meets some specification. This proves that the algorithm defined by the program is correct in the precise technical sense of being consistent with a particular specification. A program correct in this sense is free from a large and important class of errors, even though its behavior may still produce unintended results--either because the implementation of the programming language itself does not match the model of execution, or because the specification does not correctly express the user's intentions. Penelope is a prototype system for interactively developing and verifying programs that are written in a rich subset of sequential Ada. Penelope can be used to develop a program and its correctness proof incrementally, and in concert with one another. Incrementality is used in a number of ways to help make verification more tractable and more productive. For example, if an already-verified program is modified, one can attempt to prove the modified version by replaying and modifying the original verification. Penelope's specification language, Larch/Ada, belongs to the family of Larch interface languages. Larch/Ada scales up properly, in the sense that it is demonstrably sound to decompose a system hierarchically and reason locally about the implementation of each piece. Penelope has been applied in various demonstration projects--for specification (guidance control, distributed operating systems), verification (of off-the-shelf code), and formal development (by non-expert as well as expert users). Some features of Penelope have been embodied in Ada Wise, a lint-like non-interactive tool that warns of the potential for certain dynamic semantic errors in Ada programs.

Guaspari, David↗

NASA NTRS1996

Spectral imaging applications: Remote sensing, environmental monitoring, medicine, military operations, factory automation and manufacturing

This paper reviews the activities at OKSI related to imaging spectroscopy presenting current and future applications of the technology. The authors discuss the development of several systems including hardware, signal processing, data classification algorithms and benchmarking techniques to determine algorithm performance. Signal processing for each application is tailored by incorporating the phenomenology appropriate to the process, into the algorithms. Pixel signatures are classified using techniques such as principal component analyses, generalized eigenvalue analysis and novel very fast neural network methods. The major hyperspectral imaging systems developed at OKSI include the Intelligent Missile Seeker (IMS) demonstration project for real-time target/decoy discrimination, and the Thermal InfraRed Imaging Spectrometer (TIRIS) for detection and tracking of toxic plumes and gases. In addition, systems for applications in medical photodiagnosis, manufacturing technology, and for crop monitoring are also under development.

National Defense↗

NASA NTRS1998

MEMS Louvers for Thermal Control

Mechanical louvers have frequently been used for spacecraft and instrument thermal control purposes. These devices typically consist of parallel or radial vanes, which can be opened or closed to vary the effective emissivity of the underlying surface. This project demonstrates the feasibility of using Micro-Electromechanical Systems (MEMS) technology to miniaturize louvers for such purposes. This concept offers the possibility of substituting the smaller, lighter weight, more rugged, and less costly MEMS devices for such mechanical louvers. In effect, a smart skin that self adjusts in response to environmental influences could be developed composed of arrays of thousands of miniaturized louvers. Several orders of magnitude size, weight, and volume decreases are potentially achieved using micro-electromechanical techniques. The use of this technology offers substantial benefits in spacecraft/instrument design, integration and testing, and flight operations. It will be particularly beneficial for the emerging smaller spacecraft and instruments of the future. In addition, this MEMS thermal louver technology can form the basis for related spacecraft instrument applications. The specific goal of this effort was to develop a preliminary MEMS device capable of modulating the effective emissivity of radiators on spacecraft. The concept pursued uses hinged panels, or louvers, in a manner such that heat emitted from the radiators is a function of louver angle. An electrostatic comb drive or other such actuator can control the louver position. The initial design calls for the louvers to be gold coated while the underlying surface is of high emissivity. Since, the base MEMS material, silicon, is transparent in the InfraRed (IR) spectrum, the device has a minimum emissivity when closed and a maximum emissivity when open. An initial set of polysilicon louver devices was designed at the Johns Hopkins Applied Physics Laboratory in conjunction with the Thermal Engineering Branch at NASA's Goddard Space Flight Center.

Champion, J. L.↗

NASA NTRS1999

Superwinds in Seyfert Galaxies SFGs and AGN

This project was successfully completed; three refereed publications have been published on the work and the graduate student involved successfully defended his thesis. The work done in conjunction with this project demonstrated for the first time the importance of large scale winds in most if not all Seyfert galaxies and explored the physical parameters of those winds and their effect on both the interstellar medium of the host galaxy and the activity in the active nucleus as well.

Baum, Stefi↗

NASA NTRS2000

Advanced Engineering Environments for Space Transportation System Development

There are significant challenges facing today's launch vehicle industry. Global competition, more complex products, geographically-distributed design teams, demands for lower cost, higher reliability and safer vehicles, and the need to incorporate the latest technologies quicker, all face the developer of a space transportation system. Within NASA, multiple technology development and demonstration projects are underway toward the objectives of safe, reliable, and affordable access to space. New information technologies offer promising opportunities to develop advanced engineering environments to meet these challenges. Significant advances in the state-of-the-art of aerospace engineering practice are envisioned in the areas of engineering design and analytical tools, cost and risk tools, collaborative engineering, and high-fidelity simulations early in the development cycle. At the Marshall Space Flight Center, work has begun on development of an advanced engineering environment specifically to support the design, modeling, and analysis of space transportation systems. This paper will give an overview of the challenges of developing space transportation systems in today's environment and subsequently discuss the advanced engineering environment and its anticipated benefits.

Thomas, L. Dale↗

NASA NTRS1998

Joint NASA/EPA AVIRIS Analysis in the Chesapeake Bay Region: Plans and Initial Results

NASA's Ames Research Center is performing an AVIRIS demonstration project in conjunction with the U. S. Environmental Protection Agency (Region 3). NASA and EPA scientists have jointly defined a Study Area in eastern Virginia to include portions of the Chesapeake Bay, southern Delmarva Peninsula, and the mouths of the York and James Rivers. Several environmental issues have been identified for study. These include, by priority: 1) water constituent analysis in the Chesapeake Bay, 2) mapping of submerged aquatic vegetation in the Bay, 3) detection of vegetation stress related to Superfund sites at the Yorktown Naval Weapons Station, and 4) wetland species analysis in the York River vicinity. In support of this project, three lines of AVIRIS data were collected during the Wallops Island deployment on 17 August 1997. The remote sensing payload included AVIRIS, MODIS Airborne Simulator and an RC-10 color infrared film camera. The AVIRIS data were delivered to Ames from the JPL AVIRIS Data Facility, on 29 September 1997. Quicklook images indicate nominal data acquisition, and at the current time an atmospheric correction is being applied. Water constituent analysis of the Bay is our highest priority based on EPA interest and available collateral data, both from the surface and from other remote sensing instruments. Constituents of interest include suspended sediments, chlorophyll-a and accessory pigments, Analysis steps will include: verification of data quality, location of study sites in imagery, incorporation of relevant field data from EPA and other Chesapeake Bay cooperators, processing of imagery to show phenomenon of interest, verification of results with cooperators. By 1st quarter CY98 we plan to circulate initial results to NASA and EPA management for review. In the longer term we will finalize documentation, prepare results for publication, and complete any needed technology transfer to EPA remote sensing personnel.

Johnson, Lee↗

NASA NTRS2000

Free Space Laser Communications

This presentation concerns the use of Laser communication for deep space applications. The presentation reviews the problems with electromagnetic beams and then the advantages and disadvantages of the use of optical communication. The presentation then reviews some of the spacecraft technology with pictures of some of the devices. The ground reception systems and the simplified link calculation are also reviewed. Recent and planned demonstration projects are also reviewed.

Lesh, James↗