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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,621 records · Page 90
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Several specific and nonspecific responses of the human and animal body to ship noise

The effect of noise on cargo boats on a long voyage differs considerably from the effect of noise in factories and in service industries. The peculiarities of the effect of round-the-clock noises at sea at 55 to 85 decibels, typical for cargo boats, were studied in white rats in the laboratory and aboard ship (each of the experiments lasted three months) and in young naval cadets and experienced seamen on voyages lasting one, two, and three months. The findings helped to derive health standards for maximum admissible noise level at sea.

Markaryan, S. S.↗
NASA NTRS1985

Efficient implementation of real-time programs under the VAX/VMS operating system

Techniques for writing efficient real-time programs under the VAX/VMS oprating system are presented. Basic operations are presented for executing at real-time priority and for avoiding needlless processing delays. A highly efficient technique for accessing physical devices by mapping to the input/output space and accessing the device registrs directly is described. To illustrate the application of the technique, examples are included of different uses of the technique on three devices in the Langley Avionics Integration Research Lab (AIRLAB): the KW11-K dual programmable real-time clock, the Parallel Communications Link (PCL11-B) communication system, and the Datacom Synchronization Network. Timing data are included to demonstrate the performance improvements realized with these applications of the technique.

Johnson, S. C.↗
NASA NTRS1985

Rotorcraft Digital Advanced Avionics System (rodaas)

A simulator is being built to determine the practicality of using an advanced avionics system in a helicopter. Features include an autopilot; a navigation and flight planning component; an advisory system built into the computer; conventional gages and displays; a clock function; a fuel totalizer; a weight and balance computator; a performance evaluator; and emergency and normal checklists. The translation of a computer program written in PASCAL into a form that can be read by the graphics package for the simulator and basic electronic work in simulator construction are discussed.

Taira, B.↗
NASA NTRS1984

Rubidium and cesium frequency standards status and performance on the GPS program

The on-oribt operational performance of the frequency standards on the Global Positioning System (GPS) 1 to 10 NAVSTAR satellites are discussed. The history of the Rb frequency standards showing the improvements incorporated at various stages of the program and the corresponding results are presented. Also presented is the operational history of the NAVSTAR cesium frequency standards. The frequency standards configuration data presented covers the chronology of events from the concept validation satellites, NAVSTAR 1 to 10, starting in 1978 to the present, including the configurations of clocks to be used on the GPS Production Program. Data are presented showing the results of long-term laboratory testing of a production Rb frequency standard with the necessary data taken to calculate Delta F, drift, time error, and Allan variance.

Bethke, H.↗
NASA NTRS1984

New GOES satellite synchronized time code generation

The TRAK Systems' GOES Satellite Synchronized Time Code Generator is described. TRAK Systems has developed this timing instrument to supply improved accuracy over most existing GOES receiver clocks. A classical time code generator is integrated with a GOES receiver.

Fossler, D. E.↗
NASA NTRS1985

Asymmetric electroosmotic flow and mobility measurements at nonstationary positions in the rectangular chamber

The electrophoretic mobility of a cell in solution is defined by its velocity divided by the electric field strength it experiences. An obvious way to measure the mobility of cells is to apply a constant electric field to a suspension of cells in a glass chamber and clock the velocities of individual cells through a microscope. This microscope method is the classic technique in cell electrophoresis and it has been used for the bulk of research in this field. Two aspects of the microscope method can critically affect the accuracy and consistency of its cell mobility measurements: (1) the electroosmotic fluctuations in the chamber from measurement to measurement; and (2) the number of cells which can be practically measured for statistically meaningful results. A new method of analyzing microelectrophoretic data using a computer program has been developed which addresses both of these aspects. It makes possible the mobility measurements of individual cells as positions throughout the rectangular chamber depth during asymmetric electroosmotic flow.

Source record↗
NASA NTRS1985

Recording system for the solar neutron monitoring at Mt. Norikura

To monitor solar neutron events, a new recording system will be installed at Mt. Norikura Cosmic Ray Observatory. The recording system is composed of a pulse counter with clock and a microcomputer with minifloppy disk. The counter and the microcomputer are connected through the General Purpose Interface Bus line. The one minute total count of the neutron monitor is recorded on the minifloppy disk.

Yu, S. H.↗
NASA NTRS1983

Landsat-4 on-board ephemeris determination utilizing the Global Positioning System

The Global Positioning System (GPS) is a worldwide system of navigation data satellites currently being deployed by the United States for land, sea, air and space-borne users. Currently several development satellites have been launched for system evaluation. Eventually the system will include 18 operational satellites. The GPS system utilizes precision clocks to allow users to measure the one-way propagation delay of navigational signals from the satellites, so that users can infer their position by decoding the navigation signal and observing the delay from several satellites. Landsat-4 is the first spacecraft to carry a GPS navigation system into orbit. This paper describes the Landsat-4 GPS experiment, Landsat-4 requirements for ephemeris data and the in-flight performance of the system.

Korenstein, D. A.↗
NASA NTRS1985

An evaluation of Global Positioning System data for Landsat-4 orbit determination

The Navstar Global Positioning System (GPS) navigation data obtained from an experimental GPS receiver/processor package (GPSPAC) onboard the Landsat-4 spacecraft are evaluated for their accuracy and reliability for use in Landsat-4 orbit determination. Different orbit determination scenarios and methods are considered. The parameters estimated include a subset of three Landsat-4 clock parameters and an atmospheric drag coefficient, in addition to the orbital elements. It is found that Landsat-4 orbit solutions based on delta pseudorange data generally agree with the definitive solutions to the 50-meter level.

Fang, B. T.↗
NASA NTRS1984

The space orientation of stars

Stellar rotation periods recently determined from short-term variations in Ca II H and K emission-line flux associated with starspot activity can be combined with both rotational spectral-line-broadening velocity measurements and independent measurements of stellar radii to give the inclination of the star's rotation axis to the line of sight. Assuming that the limits of distribution of sunspots on the sun apply similarly to solar-type stars, interferometric measurements of stellar radii in Ca II H and K flux may be performed to determine the clock-like, on-the-plane-of-the-sky orientation as well. Various stellar-radius measuring techniques are discussed, and photon limits on the measurability of this latter parameter are derived for Ca II H and K speckle interferometry. The accuracy with which the space orientation of stars can be determined is discussed in the context of existing data as well as photon limits. The importance of determining the space orientation of stars is then discussed, with emphasis on its important application to the present search for extrasolar planetary systems.

Doyle, L. R.↗
NASA NTRS1984

Experience with 800 x 800 virtual phase and 500 x 500 three-phase CCD imagers

A description of the Galileo/Institute for Astronomy charge-coupled device (CCD) imaging system and its initial operation has been presented previously. Originally designed to operate a 500 x 500 backside illuminated three-phase CCD, the system has been modified to allow use of either the 500 x 500 sensor or the TI 800 x 800 virtual phase CCD. The modifications for the operation of the virtual phase CCD and current system performance with each type of sensor are discussed. A description is given of the implementation of various techniques discovered at the Jet Propulsion Laboratory that improve imager performance. These techniques include tri-level clocking of the virtual phase CCD to eliminate spurious charge generation in the serial register, the use of ultraviolet light flood with the backside thinned 500 x 500 three-phase device to dramatically improve the quantum efficiency in the blue, and the practical elimination of deferred charge in the three-phase device. Results of astronomical observations with each sensor are presented.

Hlivak, R. J.↗
NASA NTRS1985

GPS-based satellite tracking system for precise positioning

NASA is developing a Global Positioning System (GPS) based measurement system to provide precise determination of earth satellite orbits, geodetic baselines, ionospheric electron content, and clock offsets between worldwide tracking sites. The system will employ variations on the differential GPS observing technique and will use a network of nine fixed ground terminals. Satellite applications will require either a GPS flight receiver or an on-board GPS beacon. Operation of the system for all but satellite tracking will begin by 1988. The first major satellite application will be a demonstration of decimeter accuracy in determining the altitude of TOPEX in the early 1990's. By then the system is expected to yield long-baseline accuracies of a few centimeters and instantaneous time synchronization to 1 ns.

Yunck, T. P.↗
NASA NTRS1984

Validation of fault-free behavior of a reliable multiprocessor system - FTMP: A case study

A program of experiments has been conducted at NASA-Langley to test the fault-free performance of a Fault-Tolerant Multiprocessor (FTMP) avionics system for next-generation aircraft. Baseline measurements of an operating FTMP system were obtained with respect to the following parameters: instruction execution time, frame size, and the variation of clock ticks. The mechanisms of frame stretching were also investigated. The experimental results are summarized in a table. Areas of interest for future tests are identified, with emphasis given to the implementation of a synthetic workload generation mechanism on FTMP.

Clune, E.↗
NASA NTRS1986

Global Timing With Low- and High-Orbiting Satellites

Report summarizes method for synchronizing clocks at intercontinental distances employing satellites of Global Positioning System (GPS) in high Earth orbit and transit satellite in orbit at relatively low altitude of about 1,300 km. When fully implemented, method expected to supply precise time measurements for world-wide communication and navigation.

Wu, S. C.↗
NASA NTRS1985

Fault-free behavior of reliable multiprocessor systems: FTMP experiments in AIRLAB

This report describes a set of experiments which were implemented on the Fault tolerant Multi-Processor (FTMP) at NASA/Langley's AIRLAB facility. These experiments are part of an effort to formulate and evaluate validation methodologies for fault-tolerant computers. This report deals with the measurement of single parameters (baselines) of a fault free system. The initial set of baseline experiments lead to the following conclusions: (1) The system clock is constant and independent of workload in the tested cases; (2) the instruction execution times are constant; (3) the R4 frame size is 40mS with some variation; (4) the frame stretching mechanism has some flaws in its implementation that allow the possibility of an infinite stretching of frame duration. Future experiments are planned. Some will broaden the results of these initial experiments. Others will measure the system more dynamically. The implementation of a synthetic workload generation mechanism for FTMP is planned to enhance the experimental environment of the system.

Clune, E.↗
NASA NTRS1985

Automatic oscillator frequency control system

A frequency control system makes an initial correction of the frequency of its own timing circuit after comparison against a frequency of known accuracy and then sequentially checks and corrects the frequencies of several voltage controlled local oscillator circuits. The timing circuit initiates the machine cycles of a central processing unit which applies a frequency index to an input register in a modulo-sum frequency divider stage and enables a multiplexer to clock an accumulator register in the divider stage with a cyclical signal derived from the oscillator circuit being checked. Upon expiration of the interval, the processing unit compares the remainder held as the contents of the accumulator against a stored zero error constant and applies an appropriate correction word to a correction stage to shift the frequency of the oscillator being checked. A signal from the accumulator register may be used to drive a phase plane ROM and, with periodic shifts in the applied frequency index, to provide frequency shift keying of the resultant output signal. Interposition of a phase adder between the accumulator register and phase plane ROM permits phase shift keying of the output signal by periodic variation in the value of a phase index applied to one input of the phase adder.

Smith, S. F.↗
NASA NTRS1986

Functional and evolutionary relationships between bacteriorhodopsin and halorhodopsin in the archaebacterium, halobacterium halobium

The archaebacteria occupy a unique place in phylogenetic trees constructed from analyses of sequences from key informational macromolecules, and their study continues to yield interesting ideas on the early evolution and divergence of biological forms. It is now known that the halobacteria among these species contain various retinal-proteins, resembling eukaryotic rhodopsins, but with different functions. Two of these pigments, located in the cytoplasmic membranes of the bacteria, are bacteriorhodopsin (a light-driven proton pump) and halorhodopsin (a light-driven chloride pump). Comparison of these systems is expected to reveal structure/function relationships in these simple (primitive?) energy transducing membrane components and evolutionary relationships which had produced the structural features which allow the divergent functions. Findings indicate that very different primary structures are needed for these proteins to accomplish their different functions. Indeed, analysis of partial amino acid sequences from halo-opsin shows already that few if any long segments exist which are homologous to bacterio-opsin. Either these proteins diverged a very long time ago to allow for the observed differences, or the evolutionary clock in the halobacteria runs faster than usual.

Lanyi, J. K.↗