SEARCH · Search NASA

Results for “EUVE”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16

All sources NASA NTRS DOE OSTI

NASA NTRS1993

Detecting point sources in EUVE survey skymaps

One of the primary goals of the Extreme Ultraviolet Explorer (EUVE) all-sky survey is the detection and identification of new sources of extreme ultraviolet radiation. Here, the challenges involved in producing a catalog containing as many statistically significant detections as possible, with a small expected number of spurious detections, are reviewed. The discussion covers simulation and testing, early survey results, advanced detection techniques, and diffuse feature detection.

Lewis, J. W.↗

NASA NTRS1993

EUVE survey observations of the moon

Preliminary survey images of the moon obtained by the Extreme Ultraviolet Explorer and results of data analysis are presented. The preliminary results indicate that the brightness of the moon varies little from observation to observation. Early results also show that the lunar albedo closely matches the relative reflectivity of mineral found on the moon's surface. Further studies are conducted during the spectroscopy phase of the EUVE mission to confirm current results regarding the presence of X-ray fluorescence in the data.

Mcdonald, J. S.↗

NASA NTRS1993

Student contributions to the EUVE project

A program under which some 30 undergraduates participate in the EUVE project is briefly reviewed. The paper summarizes students' contributions to the project, the types of projects and tasks handled by the students, and skills developed as a result of the program.

Moriarta, Jennifer↗

NASA NTRS1992

Data indexing techniques for the EUVE all-sky survey

This poster describes techniques developed for manipulating large full-sky data sets for the Extreme Ultraviolet Explorer project. The authors have adapted the quatrilateralized cubic sphere indexing algorithm to allow us to efficiently store and process several types of large data sets, such as full-sky maps of photon counts, exposure time, and count rates. A variation of this scheme is used to index sparser data such as individual photon events and viewing times for selected areas of the sky, which are eventually used to create EUVE source catalogs.

Lewis, J.↗

NASA NTRS1993

Correlation of He II Lyman alpha with He I 10830 A, and with chromospheric and EUV coronal emission

This paper describes the results of comparing Solar EUV Rocket Telescope and Spectrograph (SERTS-3) images obtained in the transition region line of He II 304 A with chromospheric He I 10830 A absorption; with strong coronal lines of Mg IX 368 A, Fe XV 284 A and 417 A, and Fe XVI 335 A and 31 A; with H-alpha; with Ca II 8542 A; and with magnetograms in Fe I 8688H-alpha. All of the images are illustrated, and the image reconstruction techniques used are described and evaluated. The high correlation of the He II 304 A and He I 10830 A images, originally found by Harvey and Sheeley (1977), is confirmed and is put on a quantitative basis. We find that the supergranulation network has greater contrast, and that filaments appear darker, in 10830 A than in 304 A. In active regions, the 304 A line follows more closely the behavior of H-alpha and Ca II 8542 A than the 10830 A line.

Thompson, W. T.↗

NASA NTRS1994

Mg IX emission lines in an active region spectrum obtained with the Solar EUV Rocket Telescope and Spectrograph (SERTS)

Theoretical electron-temperature-sensitive Mg IX emission line ratios are presented for R(sub 1) = I(443.96 A)/I(368.06 A), R(sub 2) = I(439.17 A)/I(368.06 A), R(sub 3) = I(443.37 A)/I(368.06 A), R(sub 4) = I(441.22 A)/I(368.06 A), and R(sub 5) = I(448.28 A)/I(368.06 A). A comparison of these with observational data for a solar active region, obtained during a rocket flight by the Solar EUV Rocket Telescope and Spectrograph (SERTS), reveals excellent agreement between theory and observation for R(sub 1) through R(sub 4), with discrepancies that average only 9%. This provides experimental support for the accuracy of the atomic data adopted in the line ratio calculations, and also resolves discrepancies found previously when the theoretical results were compared with solar data from the S082A instrument on board Skylab. However in the case of R(sub 5), the theoretical and observed ratios differ by almost a factor of 2. This may be due to the measured intensity of the 448.28 A line being seriously affected by instrumental effects, as it lies very close to the long wavelength edge of the SERTS spectral coverage (235.46-448.76 A).

Keenan, F. P.↗

NASA NTRS1996

Development of an automated control center for the EUVE mission

The Automated Project Operations Control Center (APOCC) was developed to enable automated data acquisition, ground system management and spacecraft health and safety monitoring. The control center will be used for the Extreme Ultraviolet Explorer (EUVE) project to reduce operations staffing from three to one shift per day, while maintaining the science return and performing routine health and safety monitoring activities. The staff reduction is expected to yield a cost reduction of 250,000 dollars per year in comparison with a fully staffed, 24 hour/day operation. The APOCC infrastructure was designed to be reusable and extensible. Configurable data items are stored in data bases and spacecraft-specific information is stored in a health and safety monitoring knowledge base.

Penafiel, Catherine↗

NASA NTRS1997

Gappers and Clumpers, Cont'd. EUVE Guest Investigator Program

The objective was deep exposures of two key EUV sources, 31 Comae (GO III) and mu Vel (G5 III), to assess their coronal emission spectra in the 80-360 A interval, and any temporal variations detected in the Deep Survey telescope.

Ayres, Thomas R.↗

NASA NTRS1997

EUV line intensities above the limb measured by CDS

The extreme ultraviolet (EUV) above the limb observed with the coronal diagnostic spectrometer (CDS) are discussed. The CDS spectra were obtained up to 0.3 solar radii above the east and west limb, and above the polar coronal holes. A large data set was acquired during the campaign in August 1996. The intensities of the chromospheric, transition region and coronal lines were derived as a function of the radial distance. The density-sensitive line ratios of Si IX 350/342 A and Si X 356/347 A were used to derive an average electron density. The temperature and density in the coronal holes were found to be lower than in the closed field regions.

Fludra, A.↗

NASA NTRS1998

Temperature and Gravity Dependence of Trace Element Abundances in Hot DA White Dwarfs (94-EUVE-094)

EUV spectroscopy has shown that DA white dwarfs hotter than about 45,000 K may contain trace heavy elements, while those hotter than about 50,000 K almost always have significant abundances of trace heavy elements. One of our continuing challenges is to identify and determine the abundances of these trace constituents, and then to relate the observed abundance patterns to the present conditions and previous evolutionary histories of the hot DA white dwarfs.

Finley, David S.↗

NASA NTRS1999

Contamination Effects on EUV Optics

During ground-based assembly and upon exposure to the space environment, optical surfaces accumulate both particles and molecular condensibles, inevitably resulting in degradation of optical instrument performance. Currently, this performance degradation (and the resulting end-of-life instrument performance) cannot be predicted with sufficient accuracy using existing software tools. Optical design codes exist to calculate instrument performance, but these codes generally assume uncontaminated optical surfaces. Contamination models exist which predict approximate end-of-life contamination levels, but the optical effects of these contamination levels can not be quantified without detailed information about the optical constants and scattering properties of the contaminant. The problem is particularly pronounced in the extreme ultraviolet (EUV, 300-1,200 A) and far (FUV, 1,200-2,000 A) regimes due to a lack of data and a lack of knowledge of the detailed physical and chemical processes involved. Yet it is in precisely these wavelength regimes that accurate predictions are most important, because EUV/FUV instruments are extremely sensitive to contamination.

Tveekrem, J.↗

NASA NTRS2000

Coronal Structure: Legacy of EUVE

Extreme ultraviolet spectra (lambda lambda 70-740) and light curves (lambda lambda 75-175) of the spectroscopic binary system lambda And (HD 222107), were obtained with the Extreme Ultraviolet Explorer satellite (EUVE) in July and August 1997. Two flares were detected during the observations which spanned 15 days, or almost three-quarters of the orbital period of 20.5 days. The Emission Measure Distribution (EMD) of lambda And derived from a line-based analysis, shows an increasing slope with the temperature from 3.1x10(exp 6) K through 2.0x10(exp 7) K, as well as a remarkable 'bump' around T(sub e) approx. equals 10(exp 6.9) K. During the flares small changes were detected in both the general slope of the EMD and the height of the bump, but the bump remained very stable in its temperature. Electron densities of N(sub e) approx. equals 10(exp 12.7) cm(exp -3) are indicated at temperatures of 10(exp 7) K using Fe XXI and Fe XXII emission features.

Dupree, Andrea K.↗

NASA NTRS2000

The Storm-Time Plasmasphere as Seen by the Extreme Ultraviolet (EUV) Imager on the IMAGE Spacecraft

Many years of ground and space observations of the plasmasphere have established a basic understanding of the physics of these plasmas in the inner magnetosphere. However, many questions remain. The EUV Instrument on the IMAGE spacecraft is now providing the first ever global pictures of thermal helium in the plasmasphere. Detached plasma, the sunward extending convection tail, a night-time interior plasmaspheric density cavity, and strong azimuthal plasmaspheric structures are all being revealed. What are the properties of these structures? How do they evolve? What is their relationship to magnetic storms and other plasma populations? These are some of the questions that define the state of plasmaspheric physics, to which IMAGE is now contributing answers. The graphic evidence and preliminary analysis of these features will be presented and discussed.

Gallagher, Dennis L.↗

NASA NTRS2002

The Development of a New Model of Solar EUV Irradiance Variability

The goal of this research project is the development of a new model of solar EUV (Extreme Ultraviolet) irradiance variability. The model is based on combining differential emission measure distributions derived from spatially and spectrally resolved observations of active regions, coronal holes, and the quiet Sun with full-disk solar images. An initial version of this model was developed with earlier funding from NASA. The new version of the model developed with this research grant will incorporate observations from SoHO as well as updated compilations of atomic data. These improvements will make the model calculations much more accurate.

Warren, Harry↗

NASA NTRS1999

An EUVE Study of the B Stars Epsilon and Beta Canis Majoris

This program is a study of the comparative characteristics of the temporal variations in the extreme ultraviolet (EUV), middle ultraviolet, and optical spectral regions of the pulsating star beta Canis Majoris (beta CMa) using data from the Extreme Ultraviolet Explorer satellite. (Although the title includes two stars, only beta CMa was actually observed.) This is a program Initiated at the University of Wisconsin by J. Cassinelli and D. Cohen (now at Univ. of Delaware) and subcontracted into several components. The portion delegated to CSC (Smith) had two components: a study of the stars flux variations in the middle ultraviolet wavelength region and consulting on the pulsational characteristics of this class of stars. The research for CSC's component of this work has been to identity a group of high-resolution spectra In the final archives of the International Ultraviolet Explorer satellite and to analysis the difference between selected spectra during low and high flux phases. This analysis was carried out by binning the spectral fluxes to low resolution, taking their ratio, and examining the spectrum ratio for spectrophotometric signatures sensitive to temperature difference and density. These were calibrated against spectral flux ratios obtained from model atmospheres. These results have been completed and the results communicated to the PIs of the program. We have also communicated to them the general results of the nature of the pulsational amplitude variations both from his work and from the work of other researchers in the astronomical literature. It is expected that this work will be published soon in a refereed astronomical journal.

Smith, Myron A.↗

NASA NTRS2002

TIMED Solar EUV Experiment: Phase E

The timed Solar EUV Experiment (SEE) Phase E Annual Report for 2002 is presented. The contents include: 1) SEE Science Overview; 2) SEE Instrument Overview and Status; 3) Summary of SEE Data Products; 4) Summary of SEE Results; 5) Summary of SEE Related Talks and Papers; and 6) Future Plans for SEE Team. This paper is in viewgraph form.

Woods, Tom↗

NASA NTRS2002

IMAGE-EUV Observation of Large Scale Standing Wave Pattern in the Nightside Plasmasphere

We present analyses of a nightside plasmaspheric pattern of bifurcated, filamentary He(+) 30.4-nm emission enhancements observed by IMAGE EUV between approximately 19:40-22:13 UT on 28 June 2000 that indicate the presence of a large-scale, global ULF standing wave pattern. Analysis of coincident IMAGE magnetometer chain data reveals that these ULF waves extend across the magnetic latitude-longitude range of the chain and possess multiple spectral features between 0.6-5-mHz (3-30 minute period). Additionally, analysis of ACE SWE data reveals similarly structured spectral components in the solar wind. Collectively, these analyses lead to the conclusion that the observed large-scale ULF wave pattern is the result of solar wind pressure pulses 'ringing' the inner-magnetosphere.

Six, N. Frank↗

NASA NTRS2003

Limited Angle Reconstruction Method for Reconstructing Terrestrial Plasmaspheric Densities from EUV Images

A new method for reconstructing the global 3D distribution of plasma densities in the plasmasphere from a limited number of 2D views is presented. The method is aimed at using data from the Extreme Ultra Violet (EUV) sensor on NASA s Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite. Physical properties of the plasmasphere are exploited by the method to reduce the level of inaccuracy imposed by the limited number of views. The utility of the method is demonstrated on synthetic data.

Newman, Timothy↗