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At least 1,027 records · Page 57

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NASA NTRS1977

Flight test results of the Strapdown hexad Inertial Reference Unit (SIRU). Volume 1: Flight test summary

Flight test results of the strapdown inertial reference unit (SIRU) navigation system are presented. The fault-tolerant SIRU navigation system features a redundant inertial sensor unit and dual computers. System software provides for detection and isolation of inertial sensor failures and continued operation in the event of failures. Flight test results include assessments of the system's navigational performance and fault tolerance.

Hruby, R. J.↗

NASA NTRS1977

Detection of rings around Uranus

A description is presented of partial occultations of SAO 158687 by a series of rings around the planet Uranus. A 61-cm telescope at Perth Observatory in Western Australia was used in the investigations. Measurements were made using a conventional single-channel photometer equipped with an RCA C31034B photomultiplier. Uranus was centered in a 28-arc sec diameter aperture during the observations. An occultation of SAO 158687 by Uranus itself did not occur at Perth. However, five brief partial occultations of SAO 158687 were detected with the chart recorder. The midtimes, durations, and depths of these events are listed in a table.

Millis, R. L.↗

NASA NTRS1977

Flight test results of the strapdown hexad inertial reference unit (SIRU). Volume 2: Test report

Hruby, R. J.↗

NASA NTRS1977

Flight test results of the Strapdown hexad Inertial Reference Unit (SIRU). Volume 3: Appendices A-G

Results of flight tests of the Strapdown Inertial Reference Unit (SIRU) navigation system are presented. The fault tolerant SIRU navigation system features a redundant inertial sensor unit and dual computers. System software provides for detection and isolation of inertial sensor failures and continued operation in the event of failures. Flight test results include assessments of the system's navigational performance and fault tolerance. Selected facets of the flight tests are also described in detail and include some of the following: (1) flight test plans and ground track plots; (2) navigation residual plots; (3) effects of approximations in navigation algorithms; (4) vibration spectrum of the CV-340 aircraft; and (5) modification of the statistical FDICR algorithm parameters for the flight environment.

Hruby, R. J.↗

NASA NTRS1979

Diffuse fluxes of cosmic high-energy neutrinos

Production spectra of high-energy neutrinos from galactic cosmic-ray interactions with interstellar gas and extragalactic ultrahigh-energy cosmic-ray interactions with microwave blackbody photons are presented and discussed. These production processes involve the decay of charged pions and are thus related to the production of cosmic gamma rays from the decay of neutral pions. Estimates of the neutrino fluxes from various diffuse cosmic sources are then made, and the reasons for significant differences with previous estimates are discussed. Small predicted event rates for a DUMAND (deep underwater muon and neutrino detector) type detection system, combined with a possible significant flux of prompt neutrinos from the atmosphere above 50 TeV, may make the study of diffuse extraterrestrial neutrinos more difficult than previously thought.

Stecker, F. W.↗

NASA NTRS1982

Type 2 radio bursts, interplanetary shocks and energetic particle events

Using the ISEE-3 radio astronomy experiment data 37 interplanetary (IP) type II bursts have been identified in the period September 1978 to December 1981. These events and the associated phenomena are listed. The events are preceded by intense, soft X ray events with long decay times (LDEs) and type II and/or type IV bursts at meter wavelengths. The meter wavelength type II bursts are usually intense and exhibit herringbone structure. The extension of the herringbone structure into the kilometer wavelength range results in the occurrence of a shock accelerated (SA) event. The majority of the interplanetary type II bursts are associated with energetic particle events. These results support other studies which indicate that energetic solar particles detected at 1 A.U. are generated by shock acceleration. From a preliminary analysis of the available data there appears to be a high correlation with white light coronal transients.

Cane, H. V.↗

NASA NTRS1985

Monitoring Performance of Complex Systems

33-page report describes use of computers in automatic on-line monitoring of Centaur rocket prior to launch. Computers analyze measurements and verify events and commands. System uses adaptive software so only real problems are detected and brought to attention of engineers. Software techniques transferable to such industrial uses as batch process control and production line automation.

Thomas, W. F.↗

NASA NTRS1984

Type II solar radio bursts, interplanetary shocks, and energetic particle events

Using the ISEE-3 radio astronomy experiment data 37 interplanetary (IP) type II bursts have been identified in the period September 1978 to December 1981. These events and the associated phenomena are listed. The events are preceded by intense, soft X ray events with long decay times (LDEs) and type II and/or type IV bursts at meter wavelengths. The meter wavelength type II bursts are usually intense and exhibit herringbone structure. The extension of the herringbone structure into the kilometer wavelength range results in the occurrence of a shock accelerated (SA) event. The majority of the interplanetary type II bursts are associated with energetic particle events. These results support other studies awhich indicate that energetic solar particles detected at 1 A.U. are generated by shock acceleration. From a preliminary analysis of the available data there appears to be a high correlation with white light coronal transients.

Cane, H. V.↗

NASA NTRS1984

Severe storm identification with satellite microwave radiometry: An initial investigation with Nimbus-7 SMMR data

The severe weather characteristics of convective storms as observed by the Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) are investigated. Low 37 GHz brightness temperatures (due to scattering of upwelling radiation by precipitation size ice) are related to the occurrence of severe weather (large hail, strong winds or wind damage, tornadoes and funnel clouds) within one hour of the satellite observation time. During 1979 and 1980 over the United States there were 263 storms which had very cold 37 GHz signatures. Of these storms 15% were severe. The SMMR detected hail, wind, and tornadic storms equally well. Critical Success Indices (CSI's) of 0.32, 0.48, and 0.38 are achieved for the thresholding of severe vs. nonsevere low brightness temperature events during 1979, 1980, and the two years combined, respectively. Such scores are comparable to skill scores for early radar detection methods. These results suggest that a future geostationary passive microwave imaging capability at 37 GHz, with sufficient spatial and temporal resolution, would allow the detection of severe convective storms. This capability would provide a useful complement to radar, especially in areas not covered by radar.

Spencer, R. W.↗

NASA NTRS1988

Plume spectrometry for liquid rocket engine health monitoring

An investigation of Space Shuttle Main Engine (SSME) testing failures identified optical events which appeared to be precursors of those failures. A program was therefore undertaken to detect plume trace phenomena characteristic of the engine and to design a monitoring system, responsive to excessive activity in the plume, capable of delivering a warning of an anomalous condition. By sensing the amount of extraneous material entrained in the plume and considering engine history, it may be possible to identify wearing of failing components in time for a safe shutdown and thus prevent a catastrophic event. To investigate the possibilities of safe shutdown and thus prevent a monitor to initiate the shutdown procedure, a large amount of plume data were taken from SSME firings using laboratory instrumentation. Those data were used to design a more specialized instrument dedicated to rocket plume diagnostics. The spectral wavelength range of the baseline data was about 220 nanometers (nm) to 15 micrometer with special attention given to visible and near UV. The data indicates that a satisfactory design will include a polychromator covering the range of 250 nM to 1000 nM, along with a continuous coverage spectrometer, each having a resolution of at least 5A degrees. The concurrent requirements for high resolution and broad coverage are normally at odds with one another in commercial instruments, therefore necessitating the development of special instrumentation. The design of a polychromator is reviewed herein, with a detailed discussion of the continuous coverage spectrometer delayed to a later forum. The program also requires the development of applications software providing detection, variable background discrimination, noise reduction, filtering, and decision making based on varying historical data.

Powers, William T.↗

NASA NTRS1988

AMPTE/CCE observations of substorm-associated standing Alfven waves in the midnight sector

Magnetic-field and medium-energy particle data from the AMPTE/CCE spacecraft are used to study substorm-associated ULF pulsations in the midnight sector at a radial distance of 8 to 9 earth radii. The particle data are used to identify ion injections and to detect the electric field of ULF waves. A case study of the events on May 23, 1985 shows that the waves have the properties of a fundamental-mode standing Alfven wave. It is suggested that these observations are evidence of substorm-associated standing Alfven waves in the nightside magnetosphere.

Takahashi, K.↗

NASA NTRS1989

A statistical study of ELF-VLF plasma waves at the magnetopause

ISEE 1 plasma wave data are used to study the broadband ELF-VLF plasma waves at the magnetopause. Enhanced wave intensities are detected at 85 percent of all magnetopause crossings. Wave amplitudes vary from event to event and even with a single event. Wave spectra averaged over many passes, however, are similar at dawn, noon, and dusk local hours. The only parameter correlated with wave intensity is the magnitude of the Z component of the magnetosheath magnetic field. The results place strong constraints on any proposed generation mechanism for the broadband magnetopause boundary layer waves.

Tsurutani, Bruce T.↗

NASA NTRS1991

The spatial variations of lightning during small Florida thunderstorms

Networks of field mills (FM's) and lightning direction finders (LDF's) were used to locate lightning over the NASA KSC on three storm days. Over 90 percent of all cloud-to-ground (CG) flashes that were detected by the LDF's in the study area were also detected by the LDF's. About 17 percent of the FM CG events could be fitted to either a monopole or a dipole charge model. These projected FM charge locations are compared to LDF locations, i.e., the ground strike points. It was found that 95 percent of the LDF points are within 12 km of the FM charge, 75 percent are within 8 km, and 50 percent are within 4 km. For a storm on 22 Jul. 1988, there was a systematic 5.6 km shift between the FM charge centers and the LDF strike points that might have been caused by the meteorological structure of the storm.

Oram, Timothy D.↗

NASA NTRS1992

Probing the heliosphere with energetic hydrogen atoms

The idea of using energetic neutral atoms (ENAs), produced by charge exchange between energetic ions and ambient neutral atoms, as a diagnostic tool to investigate planetary magnetospheres from a distance has been extended to the investigation of the heliosphere. The paper explores what one can reasonably expect of the heliospheric ENA (HSENA) and what criteria would be imposed on HSENA instruments by concentrating on 10-10 exp 3 keV protons in quiet-time interplanetary space, solar-flare events, corotating interaction regions, and populations have distinctive signatures and that the detection of these particles can reveal energy spatial and propagation of ions in 3D interplanetary space, including the solar-wind termination shock. Such breadth of information could not be gained by in situ means.

Hsieh, K. C.↗

NASA NTRS1995

The effects of 8 Helios observed solar proton events of interplanetary magnetic field fluctuations

There have been recent suggestions that large fluxes during solar energetic particle events may produce their own turbulence. To verify this argument it becomes essential to find out whether these flows cause an enhancement of interplanetary magnetic field fluctuations. In the present work, power and helicity spectra of the IMF before, during and after 8 Helios-observed solar proton events in the range 0.3 - 1 AU are analyzed. In order to detect proton self generated waves, the time evolution of spectra are followed.

ValdezGalicia, J. F.↗

NASA NTRS2000

Free Flight Simulation: An Initial Examination of Air-Ground Integration Issues

The concept of "free flight" is intended to emphasize more flexibility for operators in the National Airspace System (RTCA, 1995). This may include the potential for aircraft self-separation. The purpose of this simulation was to begin examining some of the communication and procedural issues associated with self-separation in an integrated air-ground environment. Participants were 10 commercial U.S. flight crews who flew the B747-400 simulator and 10 Denver ARTCC controllers who monitored traffic in an ATC simulation. A prototypic airborne alerting logic and flight deck display features were designed to allow for increased traffic and maneuvering information. Eight different scenarios representing different conflict types were developed. The effects of traffic density (high and low) and different traffic convergence angles (obtuse, acute, and right) were assessed. Conflict detection times were found to be lower for the flight crews in low density compared to high density scenarios. For the controllers, an interaction between density and convergence angle was revealed. Analyses on the controller detection times found longer detection times in the obtuse high density compared to obtuse low density, as well as the shortest detection times in the high density acute angle condition. Maneuvering and communication events are summarized, and a discussion of future research issues is provided.

Lozito, Sandra↗

NASA NTRS2009

Integration of Airborne Aerosol Prediction Systems and Vegetation Phenology to Track Pollen for Asthma Alerts in Public Health Decision Support Systems

The residual signal indicates that the pollen event may influence the seasonal signal to an extent that would allow detection, given accurate QA filtering and BRDF corrections. MODIS daily reflectances increased during the pollen season. The DREAM model (PREAM) was successfully modified for use with pollen and may provide 24-36 hour running pollen forecasts. Publicly available pollen forecasts are linked to general weather patterns and roughly-known species phenologies. These are too coarse for timely health interventions. PREAM addresses this key data gap so that targeting intervention measures can be determined temporally and geospatially. The New Mexico Department of Health (NMDOH) as part of its Environmental Public Health Tracking Network (EPHTN) would use PREAM a tool for alerting the public in advance of pollen bursts to intervene and reduce the health impact on asthma populations at risk.

Luvall, Jeffrey C.↗

NASA NTRS2015

Characterization of the Inner Knot of the Crab: the Site of the Gamma-ray Flares?

One of the most intriguing recent discoveries has been the detection of powerful gamma-ray flares from the Crab Nebula. Such events, with a recurrence time of about once per year, can be so dramatic to make the system the brightest source in the gamma‐ray sky as occurred, e.g. in April 2011. These flares challenge our understanding of how pulsar wind nebulae work and defy current astrophysical models for particle acceleration. We present here our study of the inner knot located within a fraction of an arcsecond from the pulsar with the aim of characterizing the feature and asking if this might be the site of the origin of the gamma-ray flares. We took data using Keck, HST, and Chandra obtained as part of our multi‐wavelength campaign to identify the source of the enigmatic flares. We set an upper limit as to the gamma-ray flux from the knot. We also find that the dimensions, surface brightness, flux, etc. of the optical and infrared knot are all correlated with distance from the pulsar. This distance, in turn, varies with time. In addition to this most thorough characterization of the inner knot's properties, we examine the hypothesis that the knot may be the site of the flares by examining the knot separation versus the Fermi/LAT gamma-ray flux. Finally, as part of this research, we make use of a new approach employing singular value decomposition (SVD) for analyzing time series of images and compare the approach to more traditional methods. Our conclusions are only refined but not impacted by using the new approach.

Gamma-ray Flares↗