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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Development of a Korotkov sound processor for automatic identification of auscultatory events. I - Specification of preprocessing bandpass filters

Frequency bands that best discriminate the Korotkov sounds at systole and at diastole from the sounds immediately preceding these events are defined. Korotkov sound data were recorded from five normotensive subjects during orthostatic stress (lower body negative pressure) and bicycle ergometry. A spectral analysis of the seven Korotkov sounds centered about the systolic and diastolic auscultatory events revealed that a maximum increase in amplitude at the systolic transition occurred in the 18-26-Hz band, while a maximum decrease in amplitude at the diastolic transition occurred in the 40-60-Hz band. These findings were remarkably consistent across subjects and test conditions. These passbands are included in the design specifications for an automatic blood pressure measuring system used in conjuction with medical experiments during NASA's Skylab program.

Golden, D. P., Jr.↗
NASA NTRS1974

Evidence for an episode of crater obliteration intermediate in Martian history

It is shown that Mars experienced a brief episode of an increased obliteration rate contemporaneous with the formation of the cratered plains units. The obliteration rate during this episode was at least an order of magnitude greater than the preexisting rate. The obliteration rates prior to and after the event were identical within a factor of 3. Regional variations in the observed densities of degraded craters on the cratered terrain are shown to result from differences in the intensity of the obliteration rate during the event. The identification and characterization of the event are accomplished by using crater diameter-frequency distributions, not only for the total crater population but also for four morphological classes. Distributions are selected from 38 regions within the Martian equatorial latitudes.

Jones, K. L.↗
NASA NTRS1988

The Frasnian-Famennian mass killing event(s), methods of identification and evaluation

The absence of an abnormally high number of earlier Devonian taxa from Famennian sediments was repeatedly documented and can hardly be questioned. Primary recognition of the event(s) was based on paleontological data, especially common macrofossils. Most paleontologists place the disappearance of these common forms at the gigas/triangularis contact and this boundary was recently proposed as the Frasnian-Famennian (F-F) boundary. Not unexpectedly, alternate F-F positions were suggested caused by temporary Frasnian survivors or sudden post-event radiations of new forms. Secondary supporting evidence for mass killing event(s) is supplied by trace element and stable isotope geochemistry but not with the same success as for the K/T boundary, probably due to additional 300 ma of tectonic and diagenetic overprinting. Another tool is microfacies analysis which is surprisingly rarely used even though it can explain geochemical anomalies or paleontological overlap not detectable by conventional macrofacies analysis. The combination of microfacies analysis and geochemistry was applied at two F-F sections in western Canada and showed how interdependent the two methods are. Additional F-F sections from western Canada, western United States, France, Germany and Australia were sampled or re-sampled and await geochemical/microfacies evaluation.

Geldsetzer, H. H. J.↗
NASA NTRS1986

The identification of solar He-3-rich events and the study of particle acceleration at the sun

Kilometric radio observations are to associate type III radio bursts with solar He-3-rich events and to identify and study the sources of those events at the sun and the transport of the particles outward toward earth. The events exhibit an impulsive behavior that earns them a natural role in the event classification scheme based upon the time scale of the particle acceleration process. Multiple He-3-rich events are observed frequently from a single active region where they provide a convenient signature to test theories of particle storage and transport. These multiple events act as impulsive probes of the condition of the interplanetary medium. Their profiles contrast with the source-acceleration-induced profiles of the long-duration events from the same active region that are interspersed among them.

Reames, D. V.↗
NASA NTRS1979

Alsep data processing: How we processed Apollo Lunar Seismic Data

The Apollo lunar seismic station network gathered data continuously at a rate of 3 x 10 to the 8th power bits per day for nearly eight years until the termination in September, 1977. The data were processed and analyzed using a PDP-15 minicomputer. On the average, 1500 long-period seismic events were detected yearly. Automatic event detection and identification schemes proved unsuccessful because of occasional high noise levels and, above all, the risk of overlooking unusual natural events. The processing procedures finally settled on consist of first plotting all the data on a compressed time scale, visually picking events from the plots, transferring event data to separate sets of tapes and performing detailed analyses using the latter. Many problems remain especially for automatically processing extraterrestrial seismic signals.

Latham, G. V.↗
NASA NTRS1980

How we processed Apollo lunar seismic data

The Apollo lunar seismic station network gathered data continuously at a rate of 3 x 10 to the 8th bits per day for nearly eight years until termination in September, 1977. The data were processed and analyzed using a PDP-15 minicomputer. On average, 1500 long-period seismic events were detected yearly. Automatic event detection and identification schemes proved unsuccessful because of occasional high noise levels and, above all, the risk of overlooking unusual natural events. The processing procedures which were finally chosen consist of plotting all the data on a compressed time scale, visually picking events from the plots, transferring event data to separate sets of tapes and performing detailed analyses using the latter. Many problems remain, especially in the automatic processing of extraterrestrial seismic signals.

Nakamura, Y.↗
NASA NTRS1976

Characteristics of cosmic X-ray bursts observed with the OGO-5 satellite

Observations of 11 cosmic X-ray bursts made with the solar X-ray spectrometer aboard OGO 5 are presented. Their identification as cosmic events is based on good time coincidence with observations of cosmic gamma-ray bursts reported in the literature. The OGO-5 experiment is most sensitive to cosmic X-ray sources located in the sunward hemisphere. When this condition was satisfied and the OGO-5 experiment was operating normally, almost every cosmic gamma-ray burst reported by other observers was detected at X-ray energies of at least 32 keV. In three events the spectrum was observed down to about 10 keV. Two intense events were observed with 0.288-s time resolution, and large time variations were observed to occur in times not exceeding 0.3 s. Evidence is found that most cosmic gamma-ray bursts have photon spectra extending down to about 10 keV. The origin of these cosmic events in processes similar to those believed to occur in solar flares is briefly examined.

Kane, S. R.↗
NASA NTRS1987

Microflares in the solar magnetic network

Localized brightenings are found throughout the magnetic network in quiet sun image sequences obtained in the C IV 1548 A line by the SMM satellite's UV spectrometer and polarimeter. Some bright sites are short-lived, while others persist. Plots of the intensity fluctuations show that the enhancements at both short- and long-lived sites are the result of localized impulsive heating events that occur intermittently at the short-lived sites and in more rapid succession at the long-lived ones. The number of these events and their visibility in the wings of the C IV line are consistent with their identification as the explosive events seen in UV spectra.

Porter, J. G.↗
NASA NTRS1985

The evolution of interplanetary shocks

Unambiguous identification of the solar events associated with 48 interplanetary (IP) shocks has been facilitated by the observation of radio emission generated by the shocks. This identification makes possible an investigation of the way in which these shocks evolve and of the relationship between solar event 'strength' and shock velocity. All but two of the 48 solar events associated with IP type II radio emission included long-duration soft X-ray events (LDE's). In addition, it is shown that all intense LDE's are associated with IP shocks. A weak correlation between the integral flux of soft X-rays and the average velocity of the associated shock is suggested. However, for two events all of the usual flare signatures were absent, and the events are associated with the disappearance of solar filaments. It is shown that the shocks propagate isotropically over about 50 deg from the source site. Beyond 50 deg the shocks weaken particularly on their eastern flanks. As a consequence, shocks originating on the west limb cannot reach the earth. IP type II radio emission is dependent on shock velocity with faster shocks producing more intense emission. The study shows that radio intensities provide information about the evolution of IP shocks.

Cane, H. V.↗
NASA NTRS1994

Quantitative numerical modeling of a coronal mass ejection

The results of an investigation on how the initial state (pre-event corona) quantitatively affects the magnetohydrodynamic model output of a coronal mass ejection (CME) are presented. The extension of the study on the identification of pre-event streamer properties which are crucial in determining the observed characteristics of CMEs, to more realistic configurations, also taking into account the coronal hole regions, adjacent to quiet coronal streamers, whose physical conditions are not adequately reproduced by global coronal models, is addressed. Results from the present model show three distinct types of CME's (loop, plasmoid and spike) which correspond to the classes of CME's identified in observations made with white light coronographs. The aim is a better understanding of the intercorrelations between streamers and adjacent coronal hole properties.

Wang, A. H.↗
NASA NTRS1974

A catalogue of solar cosmic ray events: IMPS 4 and 5, May 1967 - December 1972

This catalogue of solar cosmic ray events has been prepared for the use of solar physicists and other interested scientists. It contains some 185 solar particle events detected by the Goddard Space Flight Center Cosmic Ray Experiments on IMP's IV and V (Explorer 34 and 41) for the period May 1967 - December 1972. The data is presented in the form of hourly averages for three proton energy intervals - 0.9 - 1.6 MeV; 6 - 20 MeV and 20 - 80 MeV. In addition the time histories of .5 - 1.1 MeV electrons are shown on a separate scale. To assist in the identification of related solar events, the onset time of the electron event is indicated. The details of the instrumentation and detector techniques are described. Further descriptions of data reduction procedure and on the time-history plots are given.

Vanhollebeke, M. A.↗
NASA NTRS1977

Micropulsations in the morning sector. III - Simultaneous ground-satellite observations of 10- to 45-s period waves near L = 6.6

A search for simultaneous 10- to 45-s waves at the synchronous orbit at the location of ATS 1 and at Tungsten, Northwest Territories, Canada (near the foot of the ATS 1 field line), during 1969 resulted in the identification of only one event. This event occurred near 0900-1000 LT and was identified as a Pc 3 event. By combining 1967 data from College, Alaska (near the same L shell as ATS 1), with ATS 1 data, 90 simultaneous events were identified. Analysis of 60 of these events led to the conclusion that Pi 1 are rarely, if ever, observed on the magnetic equator at synchronous orbit, even when Pi 1 activity is present on the ground near the conjugate point. Pc 3, on the other hand, are common at synchronous orbit. A statistical study of the Pc 3 occurring at ATS 1 during simultaneous College wave activity indicated characteristics similar to those observed at ATS 6.

Arthur, C. W.↗
NASA NTRS1993

Imaging with INTEGRAL

The INTEGRAL mission was proposed in response to the ESA M2 call for proposals and is dedicated to the fine spectroscopy and imaging of celestial gamma-ray sources in the energy range 15 keV to 10 MeV. Cosmic gamma-rays are emitted on a wide range of angular scales and structures for a diverse population of astronomical objects. The emission, which includes discrete spectral lines and continuum radiation is derived from point sources, localized regions, as well as a diffuse band along the Galactic plane. Much of the gamma-ray sky is composed from transient phenomena which range from the few second timescale associated with gamma-ray bursts to larger lived events lasting some days or more. These class of events pose the challenge of firstly identification and secondly that of precise positional location of 'random' short lived events which arrive isotropically. In this article the imaging requirements are evaluated in light of current observational astronomical data and practical solutions for the INTEGRAL telescope are discussed. Some of the key problems are highlighted.

Dean, A. J.↗
NASA NTRS1993

Chronology, eruption duration, and atmospheric contribution of Apollinaris Patera, Mars

Geologic mapping from Viking image data of the Martian volcano Apollinaris Patera allowed identification of 6 major events that shaped its current morphology. Derivation of new topographic data allowed accurate estimates of the volume of erupted products from which estimates of an eruption duration are presented for the edifice and its corresponding atmospheric water contribution. Topographic data were acquired using stereophotogrammetric (Viking picnos 603A42, 639A92) techniques in both profiling and contouring modes (1 km contour). The profiling mode results in a more precise measurement than the contouring mode, but is limited in its areal coverage. The contour data are used in a more general sense to provide synoptic coverage for the volcano. These new stereophotogrammetric measurements constrain the topography to an accuracy of approximately 800 m vertically and approximately 1000 m horizontally. Conversion of the derived contour map to a raster based digital elevation model (DEM) was done by a growing contours interpolation. An ambiguity arises in this volume calculation due to an uncertainty regarding the actual base of the volcano relative to the pre-existing topography. Thus, the volume estimate was bracketed by using the 100 m and the 750 m elevations, which generally correspond to the lower and upper portions of the circumferential basal scarp, respectively. The resulting volumes are 103,000 cu km and 97,000 cu km; therefore the total volume of Apollinaris Patera is estimated to be approximately 100,000 cu km.

Robinson, M. S.↗
NASA NTRS1993

Is PSR 1509-58 the remnant of supernova AD 185?

Thorsett has recently advanced the proposal that the counterpart of the supernova recorded by Chinese astronomers in AD 185 is the pulsar PSR 1509-58 in the supernova remnant MSH 15-52. This proposal is attractive since it was claimed to better fit the visibility contraints that plagued earlier identifications and since the spin-down age of the pulsar is 1690 years. I have examined in detail the question of the visibility of a supernova at the proposed position and find that the reported dates of visibility can be matched only if the supernova appeared substantially brighter than Venus at its peak. For the distance and extinction to the pulsar, this implies M(sub V) (max) was brighter than -21.4 mag, whereas the brightest known absolute magnitude of a Type II supernova is -19.65 (H(sub 0) = 75 km/s/Mpc). Thus, the high required luminosity can be used as good evidence against the identification of SN 185 with PSR 1509-58. However, if the identification is retained, then Hubble's Constant would have to have a small value and/or the supernova had to have been a type IIP event with exceptional brilliance. The earlier identification of SN 185 with MSH 14-63 by Clark and Stephenson can also be reconciled with the visibility data.

Schaefer, Bradley E.↗
NASA NTRS1975

Saturn radio emission near 1 MHz

Emission from the direction of the planet Saturn was observed by the IMP-6 spacecraft at 15 frequencies between 375 and 2200 kHz during the period April 1971 to October 1972. The Saturnian radio bursts were identified in the IMP-6 data through an analysis of the phase of the observed modulated signal detected from the spinning dipole antenna. Initial data reduction has isolated approximately 12 storms whose occurrence corresponded to times in which the spacecraft had an unobstructed view in the direction of Saturn. These events persisted over periods between one and ten minutes. Over the span of 500 days of data another 10 to 20 Saturnian events may exist, but positive identification is confused by the presence of terrestrial noise as well as a geometric ambiguity with Jupiter. A power spectral analysis of the storm occurrence times indicates a weak periodicity at 10h 30m + or - 5m at some of the observing frequencies. The spectral character of the radiation was found analogous to that of Jupiter.

Brown, L. W.↗
NASA NTRS1983

EGRET - The high energy gamma ray telescope for NASA's Gamma Ray Observatory

The EGRET high energy gamma-ray telescope under development for NASA's Gamma Ray Observatory will have an energy range of approximately 12 to 30,000 MeV, energy resolution of about 15 percent FWHM over most of that range, an effective area of about 2000 sq cm at high energies, and single photon angular accuracy of approximately 2 deg at 100 MeV, less than 0.1 deg above 5 GeV. This instrument can locate strong sources to an accuracy of about 5 arc min. The instrument utilizes a set of digital spark chambers interleaved with tantalum foils for detection and identification of gamma-ray events, and a large NaI(Tl) scintillator for energy determination. The system is triggered by a coincidence matrix using two arrays of plastic scintillation counters and a large plastic scintillator anticoincidence dome that rejects incident charged particles.

Fichtel, C. E.↗