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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 55 records · Page 3
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NASA NTRS1998

Auroral Boundaries: Comparison Between UV Images, In Situ Precipitation, and Groundbased Optical Observations

The location of poleward and equatorward boundaries are used as diagnostics of substorm phase and energy storage in the magnetosphere. Boundaries are estimated from groundbased observations (all sky imagers, meridian scanning photometers, and magnetometers), from in situ particle observations, and from spacebased global auroral observations. Each observational technique has relative advantages. Based on recent studies, different observing techniques can give differing boundary locations. Understanding any differences in the boundaries from each observing technique is important when using the data as a diagnostic for the magnetosphere. In this study, FUV auroral images from the POLAR Ultraviolet Imager are used to estimate auroral boundaries. These boundaries are then compared with similar boundaries derived from DMSP in situ particle precipitation observations and from groundbased meridian scanning photometers. The goal is to see how well the boundaries from these three dissimilar observations correlate, to estimate dependences on instrumental capabilities, i.e. imager resolution, and to serve as a potential first step to derive an algorithm for finding oval boundaries from groundbased optical data.

Germany, G. A.↗
NASA NTRS1998

Auroral Boundaries: Comparison Between UV Images, In Situ Precipitation, and Groundbased Optical Observations

The location of poleward and equatorward boundaries are used as diagnostics of substorm phase and energy storage in the magnetosphere. Boundaries are estimated from groundbased observations (all sky imagers, meridian scanning photometers, and magnetometers), from in situ particle observations, and from spacebased global auroral observations. Each observational technique has relative advantages. However, recent studies suggest caution when comparing boundaries derived from different methods. in the study, FUV auroral images from the POLAR Ultraviolet Imager are used to estimate auroral boundaries. These boundaries are then compared with similar boundaries derived from DMSP in situ particle precipitation observations and from groundbased meridian scanning photometers. The goal is to see how well the boundaries from these three dissimilar observations correlate, to estimate dependencies on instrumental capabilities, i.e. imager resolution, and to serve as a potential first step to derive an algorithm for finding oval boundaries from groundbased optical data.

Germany, G. A.↗
NASA NTRS2000

SMART Ground-based Radiation Measurements during PRIDE

We deployed a suite of ground-based remote sensing instruments - SMART (Surface Measurements for Atmospheric Radiative Transfer), at the Roosevelt Road Naval Station in Puerto Rico during the Puerto Rico Dust Experiment (PRIDE). The instruments include several solar and infrared broadband radiometers, a sunphotometer, a shadow-band radiometer, a micro-pulse lidar, a total-sky imager, a microwave radiometer, and two solar spectrometers. These radiometers were set up on a mobile platform and a solar tracker. During 27 June - 23 July, about 25 days of data were acquired under partially cloudy sky conditions. The diurnal air temperature was fluctuating around 28.6 C to within a few degrees. Daytime average of solar irradiance reaching at the surface was ranged from about 400 W/sq m on a rainy day to about 640 W/sq m on a cloud-free day. The infrared irradiance at the surface during the measurement period was averaged about 408 W/sq m. The heights of boundary layer, dusts and clouds were captured by lidar images. Based on sunphotometer and shadow-band radiometer retrievals, the aerosol optical thickness varied from below 0.1 to over 0.6. Combining with radiative transfer modeling and other in-situ and remote sensing measurements, our ground-based measurements provide vital information on understanding the long-range transport of African dust into the Caribbean.

Tsay, Si-Chee↗
NASA NTRS1988

Confusion-limited galaxy fields. I - Simulated optical and near-infrared images

Techniques for simulating images of galaxy fields are presented that extend to high redshifts and a surface density of galaxies high enough to produce overlapping images. The observed properties of galaxies and galaxy-ensembles in the 'local' universe are extrapolated to high redshifts using reasonable scenarios for the evolution of galaxies and their spatial distribution. This theoretical framework is then employed with Monte Carlo techniques to create fairly realistic two-dimensional distributions of galaxies plus optical and near-infrared sky images in a variety of model universes, using the appropriate density, luminosity, and angular size versus redshift relations.

Chokshi, Arati↗
NASA NTRS1973

Satellite-tracked cumulus velocities

The research indicates that extreme caution must be exercised in converting cloud velocities into winds. The motion of fair-weather cumuli obtained by tracking their shadows over Springfield, Missouri revealed that the standard deviation in the individual cloud motion is several times the tracking error. The motion of over-ocean cumuli near Barbados clearly indicated the complicated nature of cumulus velocities. Analysis of whole-sky images obtained near Tampa, Florida failed to show significant continuity and stability of cumulus plumes, less than 0.3 mile in diameter. Cumulus turrets with 0.3 to 2 mile in size appear to be the best target to infer the mean wind within the subcloud layers. Cumulus or stratocumulus cells consisting of x number of turrets do not always move with wind. The addition and deletion of turrets belonging to a specific cell appear to be the cause of the erratic motion of a tracer cell. It may by concluded that the accuracy of wind estimates is unlikely to be better than 2m/sec unless the physical and dynamical characteristics of cumulus motion is futher investigated.

Fujita, T. T.↗
NASA NTRS1984

The X-ray properties of high-redshift, optically selected QSOs

The X-ray properties of high redshift quasars were probed using grism/grens plates covering 13 sq deg of sky imaged to very sensitive X-ray flux levels with the Imaging Proportional Counter on the Einstein Observatory. Optical magnitudes are estimated from image diameter measurements to obtain an X-ray flux detection, or a sensitive X-ray flux upper limit, from the IPC image. Eleven out of 52 optically selected quasars are detected in X-rays at 3 sigma. The alpha ox value is 1.49 + or - 0.04 for the 52 objects.

Anderson, S. F.↗
NASA NTRS1988

Far Ultraviolot Space Telescope (FAUST)

The Far Ultraviolet Space Telescope is a compact, wide field-of-view, far ultraviolet instrument designed for observations of extended and point sources of astronomical interest. It was originally used in sounding rocket work by both French and American investigators. The instrument was modified for flight on the space shuttle and flew on the Spacelab 1 mission as a joint effort between the Laboratoire d'Astronomie Spatiale and the University of California, Berkeley. The prime experiment objective of this telescope on the Atmospheric Laboratory Applications and Science (ATLAS 1) NASA mission is to observe faint astronomical sources in the far ultraviolet with sensitivities far higher than previously available. The experiment will cover the 1300 to 1800 A band, which is inaccessible to observers on earth. The observing program during the mission consists of obtaining deep sky images during spacecraft nighttime. The targets will include hot stars and nebulae in our own galaxy, faint diffuse galactic features similar to the cirrus clouds seen by the Infrared Astronomical Satellite (IRAS), large nearby galaxies, nearby clusters of galaxies, and objects of cosmological interest such as quasars and the diffuse far ultraviolet background.

Bowyer, S.↗
NASA NTRS1988

Coherent mesoscale convection patterns during northward interplanetary magnetic field

Coincident DE 2 satellite plasma-drift and particle measurements and all-sky imaging photometer data were used to construct two-dimensional convection patterns in a study of polar ionospheric convection in the presence of subvisual-intensity soft-particle excited 6300-A sun-aligned polar cap arcs. Results show a highly anisotropic temporally stable convection with greater order than has previously been suspected.

Carlson, H. C.↗
NASA NTRS1989

The Einstein All-Sky IPC slew survey

The construction of the Einstein All-Sky Imaging Proportional Counter (IPC) slew survey is considered. It contains approximately 1000 sources between 10(exp -12) and 10(exp -10) erg/sq cm/s with a concentration toward the ecliptic poles and away from the galactic plane. Several sizable samples of bright soft X-ray selected objects for follow-up ROSAT and ASTRO-D observations and statistical study are presented. The survey source list is expected to be available by late 1989. Both paper and remote access online data base versions are to be available. An identification program is considered.

Elvis, Martin↗
NASA NTRS1991

Sondrestrom radar measurements of the reconnection electric field

The possibility of using Sondrestrom incoherent radar scatter to estimate the rate of solar-wind energy transfer is examined by using plasma-velocity measurements in the separatrix reference frame. The separatrix is the boundary between open and closed field lines, and its orientation is deduced from all-sky images. The radar observations are used to determine the separatrix location and the ionospheric plasma drift. Measurements of the reconnection electric field in the midnight sector for one night are taken, revealing that the field is less than 15 mV/m during the time of local polar-cap extension. During polar-cap contraction the field range is 30-40 mV/m, and these periods correspond to substorm expansive phases. The limitations associated with measuring ionospheric plasma drift, the boundary orientation, and boundary location are enumerated. The measurements in the experimental case demonstrate the possibility of plasma transfer from closed to open field lines.

De La Beaujardiere, O.↗
NASA NTRS1992

Mission operations technology

Developments in the area of spacecraft operations are examined that can be utilized in mission and spacecraft designs to enhance the efficiency of planetary and other mission operations. The technology enhancements described address four major systems: the spacecraft, the tracking and data system, the spaceflight operations center, and the flight projects. Specific technological advances are detailed in the areas of telemetry monitoring and fault analysis, scheduling systems, and scientific data analysis. The Spacecraft Health Automated Reasoning Prototype and the Engineering Analysis Subsystem Environment can provide real-time monitoring and analysis with limited workforce resources. The Multimission Automation for Real-time Verification of Spacecraft Engineering Link, the Operation Mission Planner, and the Sky Image Classification and Archiving Tool are other examples of systems developed by NASA that enhance operations technology by reducing the need for human input.

Varsi, Giulio↗
NASA NTRS1993

University of Wisconsin Cirrus Remote Sensing Pilot Experiment

During the period of 26 October 1989 through 6 December 1989 a unique complement of measurements was made at the University of Wisconsin-Madison to study the radiative properties of cirrus clouds. Simultaneous observations were obtained from a scanning lidar, two interferometers, a high spectral resolution lidar, geostationary and polar orbiting satellites, radiosonde launches, and a whole-sky imager. This paper describes the experiment, the instruments deployed, and, as an example, the data collected during one day of the experiment.

Ackerman, Steven A.↗
NASA NTRS1995

Results from GROCSE I: A real-time search for gamma ray burst optical counterparts

The GROCSE I experiment (Gamma-Ray Optical Counterpart Search Experiment) is a rapid slewing wide field of view optical telescope at Lawrence Livermore National Laboratory which responds to triggers from the BATSE GRB data telemetry stream that have been processed and distributed by the BACODINE network. GROCSE 1 has been in continuous automated operation since January 1994. As of October 1995, sky images for 22 GRB triggers have been recorded, in some cases while the burst was still emitting gamma rays. The preliminary analysis of eight of these events are presented here. No optical counterparts have yet been detected. Limits for optical emission are given.

Lee, B.↗
NASA NTRS1998

Particle Detectors and Data Analysis for Cusp Transient Features Campaign

On December 3, 1997, a rocket payload (36.152) was launched from Ny Alesund into the dark cusp at 0906:00 U (1206:00 LT) during an interval of southward B(sub Z), and positive B(sub y). Launch occurred during a time interval of northeastward moving auroral forms observed between 0845 and 0945 UT by ground-based meridian scanning photometers. Ground photometric measurements during the flight show that the payload passed over the poleward portion of the most intense 6300 A emissions of the dayside cusp/cleft region. Electrons of energy up to a few hundred eV were detected immediately upon instrument turn-on at an altitude of 205 km and throughout the flight until the payload reached an altitude of approximately 197 km on the downleg. Electron spectra were either quasithermal with peak energies approximately 100 eV or showed evidence of acceleration along the magnetic field line by potentials of 100-200 V. Precipitating ions were observed throughout much of the flight. Their spectra were broadly peaked in energy with the peak energy decreasing from approximately 500 eV to approximately 250 eV as the payload flew approximately westward over the dayside precipitationregion. Structure(spatial or temporal intensity variation) was observed between T + 180 s and T + approximately 400 s. At the rocket altitudes(less than 450km) the ions were observed to be precipitating. During the flight, the DMSPF-13 satellite passed through the all-sky imager field-of-view just poleward of the brightest dayside emissions enabling the identification of plasma sheet and boundary layer regions along the orbit. We thus conclude that particle fluxes detected by the rocket flight were either cusp plasma or boundary layer/mantle plasmajust poleward of the dayside cusp/cleft. Further investigation of the particle characteristics and their relationship to ionospheric convection patterns is continuing.

Sharber, James R.↗
NASA NTRS1999

Particle Detectors and Data Analysis for Cusp Transient Features Campaign

On December 3, 1997, a rocket payload (36.152) was launched from N(sub y) Alesund into the dark cusp at 0906:00 U (1206:00 LT) during an interval of southward B(sub z) and positive B(sub y). Launch occurred during a time interval of northeastward moving auroral forms observed between 0845 and 0945 UT by ground-based meridian scanning photometers. Ground photometric measurements during the flight show that the payload passed over the poleward portion of the most intense 6300 A emissions of the dayside cusp/cleft region. Electrons of energy up to a few hundred eV were detected immediately upon instrument turn-on at an altitude of 205 km and throughout the flight until the payload reached an altitude of -197 km on the downleg. Electron spectra were either quasithermal with peak energies -100 eV or showed evidence of acceleration along the magnetic field line by potentials of 100-200 V. Precipitating ions were observed throughout much of the flight. Their spectra were broadly peaked in energy with the peak energy decreasing from -500 eV to -250 eV as the payload flew approximately westward over the dayside precipitation region. Structure (spatial or temporal intensity variation) was observed between T + 180 s and T + -400 s. At the rocket altitudes (<450 km) the ions were observed to be precipitating. During the flight, the DMSP F-13 satellite passed through the all-sky imager field-of-view just poleward of the brightest dayside emissions enabling the identification of plasma sheet and boundary layer regions along the orbit. We thus conclude that particle fluxes detected by the rocket flight were either cusp plasma or boundary layer/mantle plasma just poleward of the dayside cusp/cleft. A paper describing the fields and plasmas observed during the flight is now being prepared for publication.

Sharber, James R.↗
NASA NTRS2000

Ground Based Operational Testing Of Holographic Scanning Lidars : The HOLO Experiments

Two aerosol backscatter lidar measurement campaigns were conducted using two holographic scanning lidars and one zenith staring lidar for the purposes of reliability testing under field conditions three new lidar systems and to develop new scanning measurement techniques and applications. The first campaign took place near the campus of Utah State University in Logan Utah in March of 1999 and is called HOLO-1. HOLO-2 was conducted in June of 1999 on the campus of Saint Anselm College, near the city of Manchester, New Hampshire. Each campaign covered a period of approximately one week of nearly continuous observation of cloud and aerosol backscatter in the visible and near infrared by lidar, and wide field visible sky images by video camera in the daytime. The scanning capability coupled with a high rep-rate, high average power laser enables both high spatial and high temporal resolution observations that Particularly intriguing is the possibility of deriving atmospheric wind profiles from temporal analysis of aerosol backscatter spatial structure obtained by conical scan without the use of Doppler techniques.

Schwemmer, Geary K.↗
NASA NTRS2001

A 3-Year Climatology of Cloud and Radiative Properties Derived from GOES-8 Data Over the Southern Great Plains

While the various instruments maintained at the Atmospheric Radiation Measurement (ARM) Program Southern Great Plains (SGP) Central Facility (CF) provide detailed cloud and radiation measurements for a small area, satellite cloud property retrievals provide a means of examining the large-scale properties of the surrounding region over an extended period of time. Seasonal and inter-annual climatological trends can be analyzed with such a dataset. For this purpose, monthly datasets of cloud and radiative properties from December 1996 through November 1999 over the SGP region have been derived using the layered bispectral threshold method (LBTM). The properties derived include cloud optical depths (ODs), temperatures and albedos, and are produced on two grids of lower (0.5 deg) and higher resolution (0.3 deg) centered on the ARM SGP CF. The extensive time period and high-resolution of the inner grid of this dataset allows for comparison with the suite of instruments located at the ARM CF. In particular, Whole-Sky Imager (WSI) and the Active Remote Sensing of Clouds (ARSCL) cloud products can be compared to the cloud amounts and heights of the LBTM 0.3 deg grid box encompassing the CF site. The WSI provides cloud fraction and the ARSCL computes cloud fraction, base, and top heights using the algorithms by Clothiaux et al. (2001) with a combination of Belfort Laser Ceilometer (BLC), Millimeter Wave Cloud Radar (MMCR), and Micropulse Lidar (MPL) data. This paper summarizes the results of the LBTM analysis for 3 years of GOES-8 data over the SGP and examines the differences between surface and satellite-based estimates of cloud fraction.

Khaiyer, M. M.↗
NASA NTRS2002

Bolometric detectors for the high frequency instrument on the Planck surveyor

The High Frequency Instrument (HFI) on Planck will obtain all-sky images of the Cosmic Microwave Background (CMB) and other astrophysical sources of emission with resolution of 9 arcniin at 100 GHz, 7 arcmin at 143 GHz and 5 arcniin at 217, 353, 545 and 857 GHz. The HFI focal plane will contain 48 silicon nitride micromesh bolometric detectors operating from a 100 mK heat sink. Four detectors in each of the 6 bands will detect the sum of the power in both linear polarizations. An additional 4 pair of detectors will provide sensitivity to linear polarization of emission at 143, 217 and 353 GHz. We report on the development of these detectors, which are being produced at the JPL Micro Devices Laboratory, packaged at JPL Electronics Packaging, characterized at 100 mK before delivery to our HFI consortium partners at the UWCC, UK.

Planck CMB bolometer↗