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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Latitudinal variation of thermospheric hydrogen near solstice from AE-D observations

Variations of thermospheric neutral atomic hydrogen with latitude during a solstice season near solar minimum were investigated using data acquired with the polar-orbiting AE-D satellite. Hydrogen concentrations at low latitude were found to be comparable to those found from observations with the AE-E satellite, but were slightly higher than concentrations derived from the 1983 mass spectrometer incoherent scatter atmospheric model. Results confirm the general summer-to-winter density increase, large latitudinal gradients in the summer hemisphere, and the winter enhancement of hydrogen observed in AE-C nighttime measurements. The AE-D data, however, show a small polar depression in hydrogen concentration at high winter latitudes, attributed to atmospheric dynamics following auroral heating. The density gradients observed by AE-D in the summer hemisphere were in sharp contrast to the more constant horizontal daytime profiles reported from OGO-6 and previous AE-C measurements, indicating the possibility of local time effects.

Sanatani, S.↗
NASA NTRS1992

Satellite Data for Geomagnetic Field Modeling

Satellite measurements of the geomagnetic fields began with the launch of Sputnik 3 in May of 1958 and have continued sporadically. Spacecraft making significant contributions to main field geomagnetism will be reviewed and the characteristics of their data discussed, including coverage, accuracy, resolution and data availability. Of particular interest are Vanguard 3; Cosmos 49, Ogo's -2, -4, and -6; Magsat; DE-2; and POGS. Spacecraft make measurements on a moving platfrom above the ionosphere as opposed to measurements from fixed observatories and surveys, both below the ionosphere. Possible future missions, such as Aristoteles and GOS are reviewed.

Langel, R. A.↗
NASA NTRS1994

Assessment of velocity/trajectory measurement technologies during a particle capture event

Since the early 1960s, the means to measure the time of flight (TOF) of dust grain within a mechanical detection array has existed, first in the laboratory and then in space experiments. Laboratory hypervelocity dust particle accelerators have used electrostatic detection of charge on accelerated particles for TOF and particle mass detections. These laboratory studies have led to the development of ultra-thin-film sensors that have been used for TOF measurements in dust particle space experiments. The prototypes for such devices were ultra-thin-film capacitors that were used in the OGO series of satellites. The main goal of the experimental work to be described is the development of the capability to determine the velocity vector or trajectory of a dust grain traversing an integrated dust detection array. The results of these studies have shown that the capability of detecting the charge liberated by hypervelocity dust grains with diameters in the micrometer range can be detected. Based on these results, detection systems have been designed to provide a precise analysis of the physical and dynamic properties of micrometer and submicrometer dust grains, namely the design verification unit (DVU). Through unique combinations of in situ detection systems, direct measurements of particle surface charge, velocity, momentum, kinetic energy, and trajectory have been achieved. From these measurements, the remaining physical parameters of mass, size, and density can be determined.

Tanner, William G.↗
NASA NTRS1994

Solar cyclic behavior of trapped energetic electrons in Earth's inner radiation belt

Magnetic electron spectrometer data from six satellites (OV3-3, OV1-14, OGO 5, S3-2, S3-3, and CRRES) have been used to study long-term (1966-1991) behavior of trapped energetic electrons in the inner radiation belt. Comparison of the observed energy spectra at L equal to or greater than 1.35 for different phases of the solar cycle reveals a clear trend toward enhanced fluxes during periods of solar maximum for energies below a few hundred keV; we suggest that this is caused by an increase in the rate of inward radial diffusion from a source at higher L. In contrast, for L less than 1.30, where atmospheric collisions become increasingly important, the electron flux is reduced during solar maximum; we attribute this to the expected increase in upper atmospheric densities. The electron flux above 1 MeV exhibits a systematic decay beyond 1979 to values well below the current NASA AE-8 model. This indicates that the natural background of high-energy electrons has previously been overestimated due to the long lasting presence of electrons produced by nuclear detonations in the upper atmosphere in the late 1950s and early 1960s.

Abel, Bob↗
NASA NTRS1994

Concerning flux erosion from the dayside magnetosphere

The dayside magnetopause moves inward during periods of southward interplanetary magnetic field in response to decreases in the outer magnetospheric magnetic field strength. We consider possible causes for the magnetic field strength decreases and demonstrate that they are consistent with increases in the region 1 Birkeland and cross-tail currents. We reexamine the well-known series of magnetopause crossings by OGO 5 on March 27, 1968, to demonstrate that they provide evidence for two intervals of gradual inward magnetopause motion associated with magnetic flux erosion and also for two intervals of inward magnetopause motion associated with sharp increases in the solar wind dynamic pressure.

Tsyganenko, N. A.↗
NASA NTRS1999

Crustal Magnetic Fields

Cosmos 49, Polar Orbit Geophysical Observatory (POGO) (Orbiting Geophysical Observatory (OGO-2, 4 and 6)) and Magsat have been the only low-earth orbiting satellites to measure the crustal magnetic field on a global scale. These missions revealed the presence of long- wavelength (> 500 km) crustal anomalies predominantly located over continents. Ground based methods were, for the most part, unable to record these very large-scale features; no doubt due to the problems of assembling continental scale maps from numerous smaller surveys acquired over many years. Questions arose as to the source and nature of these long-wave length anomalies. As a result there was a great stimulant given to the study of the magnetic properties of the lower crust and upper mantle. Some indication as to the nature of these deep sources has been provided by the recent results from the deep crustal drilling programs. In addition, the mechanism of magnetization, induced or remanent, was largely unknown. For computational ease these anomalies were considered to result solely from induced magnetization. However, recent results from Mars Orbiter Laser Altimeter (MOLA), a magnetometer-bearing mission to Mars, have revealed crustal anomalies with dimensions similar to the largest anomalies on Earth. These Martian features could only have been produced by remanent magnetization, since Mars lacks an inducing field. The origin of long-wavelength crustal anomalies, however, has not been completely determined. Several large crustal magnetic anomalies (e.g., Bangui, Kursk, Kiruna and Central Europe) will be discussed and the role of future satellite magnetometer missions (Orsted, SUNSAT and Champ) in their interpretation evaluated.

Taylor, Patrick T.↗
NASA NTRS2002

Ionospheric Electron/Ion Densities Temperatures on CD-ROM and WWW

As part of this project a large volume of ionospheric satellite insitu data from the sixties, seventies and early eighties were made accessible online in ASCII format for public use. This includes 14 data sets from the BE-B, Alouette 2, DME-A, AE-B, ISIS-1, ISIS-2, OGO-6, DE-2, AEROS-A, AE-C, AE-D, AE-E, and Hinotori satellites. The original data existed in various machine-specific, highly compressed, binary encoding on 7-, or 9-track magnetic tapes. The data were decoded and converted to a common ASCII data format, solar and magnetic indices were added, and some quality control measures were taken. The original intent of producing CD-ROMs with these data was overtaken by the rapid development of the Internet. Most users now prefer to obtain the data directly online and greatly value WWW-interfaces to browse, plot and subset the data. Accordingly the data were made available online on the anonymous ftp site of NASA's National Space Science Data Center (NSSDC) at ftp://nssdcftp.gsfc.nasa.gov/spacecraft data/ and on NSSDC's ATMOWeb (http://nssdc.gsfc.nasa.gov/atmoweb/), a WWW-interface for plotting, subsetting, and downloading the data. Several new features were implemented into ATMOWeb as part of this project including a filtering and scatter plot capability. The availability of this new database and WWW system was announced through several electronic mailer (AGU, CEDAR, IRI, etc) and through talks and posters during scientific meetings.

Bilitza, Dieter↗
DOE OSTI2012

Concurrent Radiotherapy and Gemcitabine for Unresectable Pancreatic Adenocarcinoma: Impact of Adjuvant Chemotherapy on Survival

Purpose: To retrospectively analyze results of concurrent chemoradiotherapy (CCRT) using gemcitabine (GEM) for unresectable pancreatic adenocarcinoma. Methods and Materials: Records of 108 patients treated with concurrent external beam radiotherapy (EBRT) and GEM were reviewed. The median dose of EBRT in all 108 patients was 50.4 Gy (range, 3.6-60.8 Gy), usually administered in conventional fractionations (1.8-2 Gy/day). During radiotherapy, most patients received GEM at a dosage of 250 to 350 mg/m{sup 2} intravenously weekly for approximately 6 weeks. After CCRT, 59 patients (54.6%) were treated with adjuvant chemotherapy (AC), mainly with GEM. The median follow-up for all 108 patients was 11.0 months (range, 0.4-37.9 months). Results: Initial responses after CCRT for 85 patients were partial response: 26 patients, no change: 51 patients and progressive disease: 8 patients. Local progression was observed in 35 patients (32.4%), and the 2-year local control (LC) rate in all patients was 41.9%. Patients treated with total doses of 50 Gy or more had significantly more favorable LC rates (2-year LC rate, 42.9%) than patients treated with total doses of less than 50 Gy (2-year LC rate, 29.6%). Regional lymph node recurrence was found in only 1 patient, and none of the 57 patients with clinical N0 disease had regional lymph node recurrence. The 2-year overall survival (OS) rate and the median survival time in all patients were 23.5% and 11.6 months, respectively. Patients treated with AC had significantly more favorable OS rates (2-year OS, 31.8%) than those treated without AC (2-year OS, 12.4%; p < 0.0001). On multivariate analysis, AC use and clinical T stage were significant prognostic factors for OS. Conclusions: CCRT using GEM yields a relatively favorable LC rate for unresectable pancreatic adenocarcinoma, and CCRT with AC conferred a survival benefit compared to CCRT without AC.

62 RADIOLOGY AND NUCLEAR MEDICINE↗