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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Analysis of Daily, Seasonal, and Interannual Changes in Hofsjokull Ice Cap, Iceland, using Satellite Data

Analysis of a time series of European Remote Sensing Satellite (ERS)-1 and -2, RADARSAT ScanSAR synthetic aperture radar (SAR) and Landsat images from 1973 to 1998, shows daily to interannual changes in Hofsjokull, a 923 sq km ice cap in central Iceland. A digital elevation model of Hofsjokull was constructed using interferometry, and then SAR backscatter coefficient (d) was plotted with elevation, and air temperature along a transect across the ice cap. Most of the a' changes measured along the transect are caused by a change in the state (frozen or thawed) of the surficial snow or ice when air temperature rises above or below about -5 to O C. Seasonal (sigma)deg patterns are identified in a 4-year time series of 57 ERS-1 and -2 images. In addition, June 1997 ScanSAR images display rapid changes in brightness that are tied closely to daily meteorological events. SAR and Landsat data were also used to measure changes in the areal extent of Hofsjokull, from 1973 to 1997, and to locate (sigma)deg and reflectance boundaries that relate to the glacier facies. Late-summer 1997 (sigma)deg and reflectance boundaries agree and are coincident with the approximate location of the fim line, and the January 1998 position of the equilibrium line as determined from ERS-2 data.

Hall, D. K.↗
NASA NTRS1984

Photoionization Structure of the Orion Nebula

The O III lines at 52 and 88 micro m and the N III line at 57 micro m were observed at 6 positions in the Orion Nebulae to probe the ionization structure of the nebula. The six positions form a line or cut south from and including the Trapezium. Electron densities and abundance ratios of N(++) were calculated and compared together with radio and optical observations. The predictions that the effects of heavy capacity in the ionized gas can cause the N(++) zone to extend appreciably beyond the O(++) zone are confirmed.

Simpson, J. P.↗
NASA NTRS1989

Zonal Winds Between 25 and 120 Km Retrieved from Solar Occultation Spectra

Atmospheric winds at heights between 25 and 120 km have been retrieved with precisions of 5/ms from the Doppler shifts of atmospheric absorption lines measured from a satellite-borne instrument. Lines of the upsilon 3 CO2 and upsilon 2 H2O rotation-vibration bands caused by gases in the instrument allowed the instrumental frequency scale to be absolutely calibrated so that accurate relative speeds could be obtained. By comparing the positions of both sets of instrumental lines the calibration of the frequency scale was determined to be stable to a precision of less than 2 x 10(-5) cm during the course of each occultation. It was found that the instrumental resolution of 0.015 cm after apodization, the signal to noise ratio of about 100 and stable calibration allowed relative speeds to be determined to a precision of 5 ms or better by using small numbers of absorption lines between 1600 and 3200 cm. Absolute absorption line positions were simultaneously recovered to precisions of 5 x 10(-5) cm or better. The wind speed profiles determined from four sunset occultations and one sunrise occultation show remarkable similarities in the magnitudes and directions of the zonal wind velocities as functions of height. These wind profiles appear to be manifestations of atmospheric tides.

Vancleef, Garrett Warren↗
NASA NTRS1991

Analysis of pressure-broadened ozone spectra in the 3 micron region

This work involves the analysis of a series of McMath Fourier Transform Infrared (FTIR) spectra of ozone broadened by mixing with air (four different pressures), nitrogen (three pressures), or oxygen (three pressures). Each spectrum covers the region from 2396 to 4057 cm(-1). This study focused on the 3 sub nu sub 3 band in t 3000 to 3060 cm(-1). The band is analyzed by first dividing its region into small intervals containing a few well isolated absorption lines of reasonable intensity. Each of these small intervals is fit by multiple iterations of the nonlinear least squares program until residuals (the difference between calculated and observed spectrum, as a percent of the strongest intensity in the interval) are minimized to a reasonable value which corresponds to the noise level of the measured spectrum. Position, intensity, and half-width are recorded for later analysis. From the measured half-widths, a pressure broadening coefficient was determined for each absorption line. Pressure shifts were determined by comparing observed line positions in the spectra of the diluted ozone samples to tabulated line positions determined from spectra of pure gas samples. Comparisons to other work on ozone indicate that the broadening and shift coefficients determined in this study are consistent with those determined in other spectral regions.

Prochaska, Eleanor S.↗
NASA NTRS1990

Rapid variability of the iron fluorescence line from the Seyfert 1 galaxy NGC6814

NGC6814, one of the faster X-ray-variable AGN, has been observed with the Large Area Counters aboard the Ginga satellite in order to obtain data on the variability of the iron fluorescence line and thus to constrain the distribution of cold gas from which the line originates. A positive correlation measured between the variability of the iron-line flux and the continuum emission suggests an upper limit of 10 to the 14th cm for the size of the ion reprocessing region.

Kunieda, Hideyo↗
NASA NTRS1990

The effect of nonequilibrium ionization on ultraviolet line shifts in the solar transition region

The line profiles and wavelength positions of all the important emission lines due to carbon were computed for a variety of steady state siphon flow loop models. For the lines from the lower ionization states (C II-C IV) a preponderance of blueshifts was found, contrary to the observations. The lines from the higher ionization states can show either a net red- or blueshift, depending on the position of the loop on the solar disk. Similar results are expected for oxygen. It is concluded that the observed redshifts cannot be explained by the models proposed here.

Spadaro, D.↗
NASA NTRS1991

First results from the Goddard High-Resolution spectrograph - High-resolution observations of the 1942 A resonance line of HG II in the chemically peculiar B star, Chi Lupi

The Goddard High-Resolution Spectrograph on the HST has been used to obtain high S/N observations of the sharp-lined, Hg- and Pt-rich B-type star, Chi Lupi, with a resolving power of 87,000. The observations reveal a level of spectroscopic detail never before observed at ultraviolet wavelengths for any star other than the sun. Concentrating on the region around the resonance line of Hg II at 1942 A, the profile and central position of this line confirm beyond doubt that the Hg isotope anomaly in Chi Lupi is real and extreme, with Hg being heavily concentrated in the form of Hg-204. The problems in atomic physics which impair the accurate analysis of spectra of this quality are emphasized.

Leckrone, David S.↗
NASA NTRS2014

Range Safety Flight Elevation Limit Calculation Software

This program was developed to fill a need within the Wallops Flight Facility workflow for automation of the development of vertical plan limit lines used by flight safety officers during the conduct of expendable launch vehicle missions. Vertical plane present-position-based destruct lines have been used by range safety organizations at numerous launch ranges to mitigate launch vehicle risks during the early phase of flight. Various ranges have implemented data submittal and processing workflows to develop these destruct lines. As such, there is significant prior art in this field. The ElLimits program was developed at NASA's Wallops Flight Facility to automate the process for developing vertical plane limit lines using current computing technologies. The ElLimits program is used to configure launch-phase range safety flight control lines for guided missiles. The name of the program derives itself from the fundamental quantity that is computed - flight elevation limits. The user specifies the extent and resolution of a grid in the vertical plane oriented along the launch azimuth. At each grid point, the program computes the maximum velocity vector flight elevation that can be permitted without endangering a specified back-range location. Vertical plane x-y limit lines that can be utilized on a present position display are derived from the flight elevation limit data by numerically propagating 'streamlines' through the grid. The failure turn and debris propagation simulation technique used by the application is common to all of its analysis options. A simulation is initialized at a vertical plane grid point chosen by the program. A powered flight failure turn is then propagated in the plane for the duration of the so-called RSO reaction time. At the end of the turn, a delta-velocity is imparted, and a ballistic trajectory is propagated to impact. While the program possesses capability for powered flight failure turn modeling, it does not require extensive user inputs of vehicle characteristics (e.g., thrust and aerodynamic data), nor does it require reams of turn data after the traditional fashion of the Air Force ranges. The program requires a nominal trajectory table (time, altitude, range, velocity, and flight elevation) and makes heavy use of it to initialize and model a failure turn.

Lanzi, Raymond J↗
NASA NTRS1937

Wind-tunnel interference with particular reference to off-center positions of the wing and to the downwash at the tail

The theory of wind tunnel boundary influence on the downwash from a wing has been extended to provide more complete corrections for application to airplane test data. The first section of the report gives the corrections of the lifting line for wing positions above or below the tunnel center line; the second section shows the manner in which the induced boundary influence changes with distance aft of the lifting line. Values of the boundary corrections are given for off-center positions of the wing in circular, square, 2:1 rectangular, and 2:1 elliptical tunnels. Aft of the wing the corrections are presented for only the square and the 2:1 rectangular tunnels, but it is believed that these may be applied to jets of circular and 2:1 elliptical cross sections. In all cases results are included for both open and closed tunnels.

Silverstein, Abe↗
NASA NTRS2013

Implementation of a Novel Low-Cost Low-Profile Ku-Band Antenna Array for Single Beam Steering from Space

Phased array antennas afford many advantages over traditional reflector antennas due to their conformality, high aperture efficiency, and unfettered beam steering capability at the price of increased cost and complexity. This paper eliminates the complex and costly array backend via the implementation of a series fed array employing a propagation constant reconfigurable transmission line connecting each element in series. Scanning can then be accomplished through one small (less than or equal to 100mil) linear motion that controls propagation constant. Specifically, each element is fed via a reconfigurable coplanar stripline transmission line with a tapered dielectric insert positioned between the transmission line traces. The dielectric insert is allowed to move up and down to control propagation constant and therefore induce scanning. We present a 20 element patch array design, scanning from -25 deg. less than or equal to theta less than or equal to 21 deg. at 13GHz. Measurements achieve only10.5 deg. less than or equal to theta less than or equal to 22 deg. scanning due to a faulty, yet correctable, manufacturing process. Beam squint is measured to be plus or minus 3 deg. for a 600MHz bandwidth. This prototype was improved to give scanning of 3.5 deg. less than or equal to theta less than or equal to 22 deg. Cross-pol patterns were shown to be -15dB below the main beam. Simulations accounting for fabrication errors match measured patterns, thus validating the designs.

Reconfigurable Transmission Lines↗
NASA NTRS1996

ROSAT PSPC spectra of X-ray selected narrow emission line galaxies

The Rosat Position Sensitive Proportional Counter (PSPC) spectra of a sample of 35 X-ray selected Narrow Emission Line Galaxies (NELGs) are presented. Of these 35 objects, 16 are from the Rosat International X-ray Optical Survey (RIXOS) and the remaining 19 were discovered during the optical identification of Rosat U.K. deep survey sources. A power law model with low energy absorption set at the Galactic value is found to be a good fit for all sources. The results indicate that the spectral slope of NELGs is flatter than that of active galactic nuclei.

Colmenero, E. Romero↗
NASA NTRS1985

Retinally stabilized differential resolution television display

A remote television viewing system employing an eye tracker is disclosed, wherein a small region of the image appears in high resolution, and the remainder of the image appears in low resolution. The eye tracker monitors the position of the viewer's line of sight. The eye tracker position data is transmitted to the remote television camera and control. Both the remote camera and television display are adapted to have selectable high-resolution and low resolution raster scan modes. The position data from the eye tracker is used to determine the point at which the high-resolution scan is to commence. The video data defining the observed image is encoded in a novel format, wherein in each data field, the data representing the position of the high resolution region of predetermined size appears first, followed by the high resolution zone video data and then the low-resolution region data. As the viewer's line of sight relative to the displayed image changes, the position of the high resolution region changes to track the viewer's line of sight.

Ruoff, C. F., Jr.↗
NASA NTRS1943

Determination of the Mass Moments and Radii of Inertia of the Sections of a Tapered Wing and the Center-of-Gravity Line along the Wing Span

For computing the critical flutter velocity of a wing among the data required are the position of the line of centers of gravity of the wing sections along the span and the mass moments and radii of inertia of any section of the wing about the axis passing through the center of gravity of the section. A sufficiently detailed computation of these magnitudes even if the weights of all the wing elements are known, requires a great deal of time expenditure. Thus a rapid competent worker would require from 70 to 100 hours for the preceding computations for one wing only, while hundreds of hours would be required if all the weights were included. With the aid of the formulas derived in the present paper, the preceding work can be performed with a degree of accuracy sufficient for practical purposes in from one to two hours, the only required data being the geometric dimensions of the outer wing (tapered part), the position of its longerons, the total weight of the outer wing, and the approximate weight of the longerons, The entire material presented in this paper is applicable mainly to wings of longeron construction of the CAHI type and investigations are therefore being conducted by CAHI for the derivation of formulas for the determination of the preceding data for wings of other types.

Savelyev, V. V.↗
NASA NTRS1974

Analysis of the 0.511 MeV radiation at the OSO-7 satellite

Observations of the 0.511 MeV positron annihilation, gamma ray on the OSO-7 satellite are presented. Variables which affect the counting rate are discussed. An upper limit flux of .0076 photons/sq cm/sec is obtained for the quiet sun and a positive solar flux of .063(+ or - .0002) photons/sq cm/sec is obtained for the 3B flare of 4 August 1972. The width of this annihilation line gives an upper limit temperature for the annihilation region of approximately 6 million K. An analysis of the line width and position also shows that the contribution to the line from positronium annihilation is less than 100% at the 99% confidence level. An upper limit is also found for an isotropic cosmic flux.

Dunphy, P. P.↗
NASA NTRS1986

The ionization structure of the Orion nebula: Infrared line observations and models

Observations of the (O III) 52 and 88 micron lines and the (N III) 57 micron line have been made at 6 positions and the (Ne III) 36 micron line at 4 positions in the Orion Nebula to probe its ionization structure. The measurements, made with a -40" diameter beam, were spaced every 45" in a line south from and including the Trapezium. The wavelength of the (Ne III) line was measured to be 36.013 + or - 0.004 micron. Electron densities and abundance ratios of N(++)/O(++) have been calculated and compared to other radio and optical observations. Detailed one component and two component (bar plus halo) spherical models were calculated for exciting stars with effective temperatures of 37 to 40,000K and log g = 4.0 and 4.5. Both the new infrared observations and the visible line measurements of oxygen and nitrogen require T sub eff approx less than 37,000K. However, the double ionized neon requires a model with T sub eff more than or equal to 39,000K, which is more consistent with that inferred from the radio flux or spectral type. These differences in T sub eff are not due to effects of dust on the stellar radiation field, but are probably due to inaccuracies in the assumed stellar spectrum. The observed N(++)/O(++) ratio is almost twice the N(+)/O(+) ratio. The best fit models give N/H = 8.4 x 10 to the -5 power, O/H = 4.0 x 10 to the -4 power, and Ne/H = 1.3 x 10 to the -4 power. Thus neon and nitrogen are approximately solar, but oxygen is half solar in abundance. From the infrared O(++) lines it is concluded that the ionization bar results from an increase in column depth rather than from a local density enhancement.

Simpson, J. P.↗
NASA NTRS2017

Close Range Photogrammetry in Space - Measuring the On-Orbit Clearance between Hardware on the International Space Station

When photogrammetrists read an article entitled "Photogrammetry in Space" they immediately think of terrestrial mapping using satellite imagery. However in the last 19 years the roll of close range photogrammetry in support of the manned space flight program has grown exponentially. Management and engineers have repeatedly entrusted the safety of the vehicles and their crews to the results of photogrammetric analysis. In February 2010, the Node 3 module was attached to the port side Common Berthing Mechanism (CBM) of the International Space Station (ISS). Since this was not the location at which the module was originally designed to be located on the ISS, coolant lines containing liquid ammonia, were installed externally from the US Lab to Node 3 during a spacewalk. During mission preparation I had developed a plan and a set of procedures to have the astronauts acquire stereo imagery of these coolant lines at the conclusion of the spacewalk to enable us to map their as-installed location relative to the rest of the space station. Unfortunately, the actual installation of the coolant lines took longer than expected and in an effort to wrap up the spacewalk on time, the mission director made a real-time call to drop the photography. My efforts to reschedule the photography on a later spacewalk never materialized, so rather than having an as-installed model for the location of coolant lines, the master ISS CAD database continued to display an as-designed model of the coolant lines. Fast forward to the summer of 2015, the ISS program planned to berth a Japanese cargo module to the nadir Common Berthing Mechanism (CBM), immediately adjacent to the Node 3 module. A CAD based clearance analysis revealed a negative four inch clearance between the ammonia lines and a thruster nozzle on the port side of the cargo vehicle. Recognizing that the model of the ammonia line used in the clearance analysis was "as-designed" rather than "as-installed", I was asked to determine the real clearance between the ammonia lines and expected position of the thruster bell using existing on-orbit imagery. Imagery of the area of interest, taken several years earlier from the Space Shuttle during a fly-around of the ISS, was found and used to set a stereo pair. Space Vision System Targets and Handrail bolts measured in the ISS analytical coordinate system (ISSACS) prior to launch, were used to obtain an absolute orientation so all photogrammetric measurement's would be in the ISSACS coordinate system. Coordinates for the design location of the edges of the thruster bell, when the cargo vehicle was fully berthed to the ISS, were displayed in 3-D relative to the as-installed ammonia lines. This immediately revealed a positive clearance, which was later quantified to be a minimum of 10" +/0.5". The analysis was completed over a single weekend by a single analyst. Using updated imagery, acquired from the station's robotic arm, a complete as-installed model of the coolant lines was generated from stereo photography and replaced the design model in the master ISS CAD database.

Liddle, Donn↗
NASA NTRS1991

Axisymmetric model of the ionized gas in the Orion Nebula

New ionization and thermal equilibrium models for the ionized gas in the Orion Nebula with an axisymmetric two-dimensional 'blister' geometry/density distribution are presented. The HII region is represented more realistically than in previous models, while the physical detail of the microphysics and radiative transfer of the earlier spherical modeling is maintained. The predicted surface brightnesses are compared with observations for a large set of lines at different positions to determine the best-fitting physical parameters. The model explains the strong singly ionized line emission along the lines of sight near the Trapezium.

Rubin, R. H.↗