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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

High spatial resolution infrared imaging of L1551-IRS 5 - Direct observations of its circumstellar envelope

Images of L1551-IRS 5 were obtained at 1.65, 2.2, and 3.8 microns using the University of Rochester's Infrared Array Camera. It is found that IRS 5 is spatially resolved, and that it is elongated: the observed FWHM size of IRS 5 is 4.1 x 2.8 arcsec-squared at 2.2 microns. These observations are interpreted in terms of a flattened circumstellar envelope that is viewed from about 18 deg above its equatorial plane, a configuration that has been treated theoretically by Lefevre et al. In this model the central star is not seen directly, but only light scattered toward the observer from the visible polar region, where the envelope is thinnest, is observed. It is deduced that the envelope has a diameter of 1000 AU, a molecular hydrogen density of greater than or approximately equal to 4 x 10 to the 6th/cu cm, and a mass of greater than or approximately equal to 0.02 M solar mass, which results in an extinction of Av greater than about 33 mag to the central source.

Moneti, Andrea↗
NASA NTRS1989

High spatial resolution far-infrared scans of W3(OH)

The strong far-infrared continuum source associated with the OH maser-ultracompact H II region W3(OH) was observed from the Kuiper Airborne Observatory in order to determine its size at 50 and 100 microns. Maximum entropy deconvolutions of the slit scans made in orthogonal directions across the source show it to be approximately circular with FWHM sizes of 8 arcsec and 13 arcsec at 50 and 100 microns, respectively. For these sizes, W3(OH) is optically thick in the far-infrared. A spherically symmetric, dusty molecular cloud model is developed to fit the data.

Campbell, M. F.↗
NASA NTRS1989

Cloud field classification based upon high spatial resolution textural features. II - Simplified vector approaches

This paper compares the results of cloud-field classification derived from two simplified vector approaches, the Sum and Difference Histogram (SADH) and the Gray Level Difference Vector (GLDV), with the results produced by the Gray Level Cooccurrence Matrix (GLCM) approach described by Welch et al. (1988). It is shown that the SADH method produces accuracies equivalent to those obtained using the GLCM method, while the GLDV method fails to resolve error clusters. Compared to the GLCM method, the SADH method leads to a 31 percent saving in run time and a 50 percent saving in storage requirements, while the GLVD approach leads to a 40 percent saving in run time and an 87 percent saving in storage requirements.

Chen, D. W.↗
NASA NTRS1990

High spatial resolution studies of galaxies in the far IR: Observations with the KAO, and the promise of SOFIA

NASA, in collaboration with the West German Science Ministry (BMFT), plans a larger airborne telescope as a successor to the Kuipper Airborne Observatory (KAO) that will achieve these goals. The Stratospheric Observatory for Infrared Astronomy (SOFIA) is entering the final stages of Phase B review with targeted new start early in the next decade. SOFIA is a 2.7 m diameter telescope that is carried in a Boeing 747SP. In addition to having 3 times the spatial resolution of the KAO, and 10 times the light gathering power, it will incorporate improvements over the KAO in lower optical emissivity and better telescope tracking stability. The thin primary mirror will equilibrate quickly to ambient temperature at an altitude which, accompanied by airflow improvements across the telescope cavity, will result in better image quality. The sensitivity of SOFIA will allow us to see a large number of typical bright galactic HII regions in local group galaxies. The spatial resolution of 8 seconds (full width half maximum Airy disk) at 100 microns will allow these regions to be measured independently, if they are distributed similarly to those in our own galaxy. At this spatial resolution, the disks of normal galaxies will be easily resolved out to distances of several hundred Mpc. This portion of space includes many of the superluminous galaxies discovered by the Infrared Astronomy Satellite (IRAS), and this spatial scale is relevant for studies of the morphology of regions of interaction among the majority of these galaxies that are members of colliding pairs.

Lester, Dan F.↗
NASA NTRS1991

High-spatial-resolution passive microwave sounding systems

During this period the emphasis was on the following: (1) further design, construction, and testing of the improved 54-GHz portion of the 54-118 GHz microwave temperature sounder (MTS) aircraft radiometer system in preparation for ER-2 observations in July 1991; and (2) final analysis and documentation of procedures for detecting and analyzing thermal waves in our 118-GHz MTS imagery. In addition, we have new unpublished measurements of dry-air attenuation at frequencies of 54 to 66 GHz and over a temperature range of 280K to 326K; these measurements should enable us to improve further our atmospheric transmittance models. It was further noted that the proposed SSMIS conical-scanning microwave spectrometer on the military DMSP Block 5D-3 spacecraft designed to measure stratospheric and mesospheric temperature profiles will be observing the Zeeman-split oxygen lines with sufficient spectral resolution that the changing Doppler shifts with view angle will substantially degrade the potential system performance unless remedied; this was briefly studied and documented.

Staelin, David H.↗
NASA NTRS1994

High spatial resolution telescopic multispectral imaging and spectroscopy of the Moon. 1: The Serenitatis/Tranquillitatis border region

The region of the moon near the border between Mare Serenitatis and Mare Tranquillitatis is one of the most geologically and compositionally complex areas of the nearside. The geologic history of this region has been shaped by impacts of widely-varying spatial scale and temporal occurrence, by volcanism of variable style and composition with time, and by limited tectonism. We have been studying this region as part of a larger multi remote sensing technique effort to understand the composition, morphology, geology, and stratigraphy of the moon at spatial scales of 2 km or less. The effort has been aided by the proximity of this area to the Apollo 11, 15, and 17 landing sites and by the occurrence of one of the primary lunar spectroscopic 'standard areas' within our scene (MS2). Here, some of the findings from the multispectral imaging and spectroscopy part of this effort are reported.

Bell, James F., III↗
NASA NTRS1994

Implications of high-spatial-resolution thermal infrared (Termoskan) data for Mars landing site selection

Thermal infrared observations of Mars from spacecraft provide physical information about the upper thermal skin depth of the surface, which is on the order of a few centimeters in depth and thus very significant for lander site selection. The Termoskan instrument onboard the Soviet Phobos '88 spacecraft acquired the highest spatial-resolution thermal infrared data obtained for Mars, ranging in resolution from 300 m to 3 km per pixel. It simultaneously obtained broadband reflected solar flux data. Although the 6 deg N - 30 deg S Termoskan coverage only slightly overlaps the nominal Mars Pathfinder target range, the implications of Termoskan data for that overlap region and the extrapolations that can be made to other regions give important clues for optimal landing site selection.

Betts, Bruce H.↗
NASA NTRS1994

Optical imaging and high spatial resolution 21 cm H I observations of the peculiar galaxy NGC 2782 (Arp 215)

We have used the Very Large Array (VLA) B and C Arrays to make 21 cm H I observations of the peculiar galaxy NGC 2782 (Arp 215). These observations are complementary to previously published D Array VLA data, which revealed the presence of a long (5 min to 54 kpc) H I plume near the western side of this galaxy. We have also obtained BVRI H alpha images of the main body of this galaxy using the McDonald Observatory 30 inch telescope. The optical images of this galaxy show a strong stellar tail extending to the east, opposite the H I plume. Within the disk of NGC 2782, unsharp masking of the optical images at all 4 broadband wavelengths reveals three bright 'ripples', separated by approximately 15 sec. The light profiles across these ripples are symmetric, without a sharp outer edge. H alpha is strong at the starburst nucleus and along the northern and western sections of the inner ripple. The new higher resolution H I data show that the atomic gas is very clumpy. We have identified ten H I clumps in the long western plume, with H I masses of approximately 10(exp 8) solar mass, similar to those of dwarf galaxies, and column densities of approximately 10(exp 21) cm(exp -2) over surface areas of approximately 10 kpc(exp 2). No CO (1-0) emission has been detected from this plume, suggesting that it is material stripped from the outer edge of a disk galaxy. The H alpha peaks, in contrast, are generally not coincident with H I peaks. No H I is seen at the tip of the eastern extension. The H I distribution near this structure is ring-like rather than tail-like as in the optical data. We have detected redshifted H I absorption toward the central continuum source, indicating gas infall into the nuclear region. Using a restricted 3-body dynamical model, we have successfully reproduced the basic properties of NGC 2782 with an off-center collision between two galaxies, where a lower mass disk companion (M(sub 2)/M(sub 1) approximately 0.25) collides almost head-on with a larger disk galaxy. In this scenario, the companion becomes the eastern extension, and the long western tail is material pulled out from the larger galaxy. The lack of H I at the tip of the eastern tail may be due to stripping during the collision. Alternative formation scenarios include a merger or interaction between two disk galaxies, where the ripples may be due to a disturbed spiral density wave or galactic winds due to the central starburst.

Smith, Beverly J.↗
NASA NTRS1990

High spatial resolution restoration of IRAS images

A general technique to improve the spatial resolution of the IRAS AO data was developed at The Aerospace Corporation using the Maximum Entropy algorithm of Skilling and Gull. The technique has been applied to a variety of fields and several individual AO MACROS. With this general technique, resolutions of 15 arcsec were achieved in 12 and 25 micron images and 30 arcsec in 60 and 100 micron images. Results on galactic plane fields show that both photometric and positional accuracy achieved in the general IRAS survey are also achieved in the reconstructed images.

Grasdalen, Gary L.↗
NASA NTRS1997

High Spatial Resolution Studies of Blastwave Interactions in the Vela Supernova Remnant

The report targeted two interaction zones within the Vela supernova remnant for HRI observation and data reduction and analysis. Approximately 40 ksec of HRI integration time was awarded for each of the awarded target regions, one at priority 2 and one at priority 3. The observations have been completed for the priority 2 observation. Some observations have been made of the priority 3 target, however the data have not yet been received by the PI. The priority 2 data have been received and analyzed and the results have been prepared for publication. The chief results are as follows: (1) the radial profile of the X-ray emission from the western rim is characterized by a sudden increase in emission at the blastwave interaction region which is unresolved spatially at HRI resolution. The profile is consistent with the expanding blastwave from the remnant encountering a large, coherent structure in the surrounding ISM; (2) the X-ray emission lags slightly 'behind', approx. 10(exp 16)cm the H(alpha) and OIII optical filaments, consistent with the expected spatial profile of the emission assuming parameters derived from earlier PSPC observations of the region. the combination of the X-ray and optical interference filter data allow us to set limits on the distance to the Vela remnant and the general nature of the blastwave interactions in the remnant.

Craig, William↗
NASA NTRS1998

Analyses at High Spatial Resolution of Organic Molecules in Extraterrestrial Samples: Two-Step Laser Mass Spectrometry: Search for Polycyclic Aromatic Hydrocarbons in Antarctic Meteorite and Micrometeorite Samples

Perhaps the best way to summarize the past three-year grant period is to cite the publications and present a brief synopsis of each: 1. "Indigenous Polycyclic Aromatic Hydrocarbon Molecules in Circumstellar Graphite Grains." Bulk C-12/C-13 isotope ratios observed in some graphite grains extracted from primitive meteorites point strongly to a circumstellar origin. By applying our technique of microprobe two-step laser desorption laser ionization mass spectrometry ((mu)L(sup 2)MS) to individual circumstellar graphite grains we have measured the C-12/C-13 isotope ratio of various polycyclic aromatic hydrocarbons (PAHS) found in these grains. 2. "Deuterium Enrichments in Cluster IDPS," Large enrichments in the D/H isotope ratios in IDPs likely arise from the preservation of presolar molecules. 3. "Evidence for thermalization of surface-disorder molecules at heating rates of 10(exp 8) K/s". A careful study of the ((mu)L(sup 2)MS) of aniline-d(sub 7) from a single-crystal surface (0001) of sapphire (al2O3) shows that all measured properties are consistent with a thermal mechanism for desorption. 4. "Search for past life on Mars; possible relic biogenic activity in Martian meteorite ALH 84001. The authors examined the Martian meteorite ALH 84001 and found several lines of evidence compatible with existence of past primitive (single-cell) life on early Mars. 5. "Microprobe two-step laser mass spectrometry as an analytical tool for meteorite samples". THis paper presents a comprehensive review of (mu)L(sup 2)MS and how this technique can be applied to meteoritic samples. 6. "Indigenous polycyclic aromatic hydrocarbons in circumstellar graphite grains from primitive meteorites". The C-12/C-13 isotope ratios were measured for PAHs in a total of 89 spherical graphite grains. 7. "Observation of indigenous polycyclic aromatic hydrocarbons in "Giant" carbonaceous antarctic micrometeorites." The (mu)L(sup 2)MS method was used to establish the nature and distribution of PAHs in fragments of fifteen (approx. 200 microns) carbonaceous antarctic micrometeorites (AMMs). 8. "Evidence for the extraterrestrial origin of polycyclic aromatic hydrocarbons in the Martian meteorite ALH 84001" We have undertaken additional contamination studies of ALH 84001.

Zare, Richard N.↗
NASA NTRS2000

A High Spatial Resolution Study of Far IR Emission of Galaxies

This grant funded observations, data reduction, professional publications and travel for scientific efforts on the Kuiper Airborne Observatory. The research project was successfully completed. New insights into the distribution of far infrared emission across star forming regions was obtained, and student training was achieved. The efforts contributed towards new observing strategies, such as calibration and intercomparison of data from different infrared astronomical observing platforms, that will impact future NASA missions, such as SOFIA. The results of the effort have been presented in several papers in the refereed literature, including: "The Structure of IR Luminous Galaxies at 100 Microns". " Far Infrared Thermal Emission from the Inner Cooling Flow Region of NGC1275". "Distribution of Light in the "Dusty Hand" Galaxy NGC2146".

Caldwell, Barrie A.↗
NASA NTRS2002

High Spatial Resolution Thermal Remote Sensing of the Urban Heat Island Effect: Assessment of Risks to Human Health and Development of Mitigation Strategies for Sustainable Cities

The growth of cities, both in population and in areal extent, appears as an inexorable process. Urbanization continues at a rapid rate, and it is estimated that by the year 2025, 80% of the world's population will live in cities. One of the more egregious side effects of urbanization is the deterioration in air quality as a result of increased vehicular traffic, industrialization and related activities. In the United States alone, under the more stringent air quality guidelines established by the U.S. Environmental Protection Agency (EPA) in 1997, nearly 300 counties in 34 states will not meet the new air quality standards for ground level ozone. The mitigation of one the physical/environmental characteristics of urbanization known as the urban heat island (UHI) effect, is now being looked at more closely as a possible way to bring down ground level ozone levels in cities and assist states in improving air quality. The UHI results from the replacement of "natural" land covers (e.g., trees, grass) with urban land surface types, such as pavement and buildings. Heat stored in these surfaces is released into the air and results in a "dome" of elevated air temperatures that presides over cities. The effect of this dome of elevated air temperatures is known as the UHI, which is most prevalent about 2-3 hours after sunset on days with intense solar radiation and calm winds. Given the local and regional impacts of the UHI, there are significant potential affects on human health, particularly as related to heat stress and ozone on body temperature regulation and on the cardiovascular and respiratory systems. In this study we are using airborne and satellite remote sensing data to analyze how differences in the urban landscape influence or drive the development of the UHI over four U.S. cities. Additionally, we are assessing what the potential impact is on risks to human health, and developing mitigation strategies to make urban areas more environmentally sustainable.

Quattrochi, Dale A.↗
NASA NTRS2002

Radiometric and Spatial Characterization of High-Spatial Resolution Sensors

The development and improvement of commercial hyperspatial sensors in recent years has increased the breadth of information that can be retrieved from spaceborne and airborne imagery. NASA, through it's Scientific Data Purchases, has successfully provided such data sets to its user community. A key element to the usefulness of these data are an understanding of the radiometric and spatial response quality of the imagery. This proposal seeks funding to examine the absolute radiometric calibration of the Ikonos sensor operated by Space Imaging and the recently-launched Quickbird sensor from DigitalGlobe. In addition, we propose to evaluate the spatial response of the two sensors. The proposed methods rely on well-understood, ground-based targets that have been used by the University of Arizona for more than a decade.

Thome, Kurtis↗
NASA NTRS2003

A Sounding Rocket Investigation of the Fine Structure in the Mesopause Region in Conjunction with High Spatial Resolution Lidar Measurements

The grant funds were provided to carry out chemical tracer wind and turbulence measurements in the mesosphere and lower thermosphere as part of the Turbulent Oxygen Mixing Experiment (TOMEX) for which Dr. James Hecht of the Aerospace Corp. was the Principal Investigator. Clemson University designed, built, and tested two chemical tracer release payload sections for the 21.126 and 21.127 payloads which, in addition, had photometer and ionization gauge instrumentation. The tracer chemical was trimethyl aluminum (TMA). The experiment was carried out at White Sands Missile Range in New Mexico on October 26,2000. The location was chosen because of the proximity to the Starfire Optical Range (SOR) which hosted the powerful University of Illinois sodium lidar for an extended period prior to and also during the launch window. Since the SOR telescope is fully steerable, lidar measurements in the same volume sampled by the rocket were possible. The primary objective of the experiment was to measure the turbulent diffusion and mixing in the mesosphere and lower thermosphere, especially in layers characterized by convective and/or dynamical instabilities. The lidar, which is capable of measuring the sodium density, temperatures, and winds with good range and time resolution, provided the launch criteria, as well as context measurements for the in situ rocket observations.

Larsen, M. F.↗
NASA NTRS2001

In-Flight Edge Response Measurements for High Spatial Resolution Remote Sensing Systems

In-flight measurement of spatial resolution were conducted as part of the ASA Scientific Data Purchase (SDP) Validation and Verification (V&V) process. Characterization included remote sensing systems with ground sample distance (GSD) of 1 meter or less, such as the panchromatic imager on-board the ICONOS satellite and the airborne ADAR System 5500 multispectral instrument. Final image products were used to evaluate the effect of both the image acquisition system (e.g., optics, electronics, motion, jitter, atmosphere) and image post-processing (e.g., resampling, modulation trasfer function (MTF) compensator). Spatial resolution was characterized by full width at half maximum (FWHM) of an edge response-derived line spread function. This was found to be a more robust measure of spatial resolution than the value of NTF at Nyquist frequency The edge responses were analysed using the tilted-edge technique that ovecomes the spatial sampling limitations of the digital imaging systems. As an enhancement to existing algorithms, the slope of the edge response and the orientation of the edge target were determined by a single computational process. Adjacent black and white square panels, either painted on a flat surface or deployed as traps, formed the ground-based edge targets used in the tests. Orientation of the deployable tarps was optimized beforehand, based on simulations of the imaging system. Numerous edge target images were analyzed for each of the tested sensors. The effect of such factors as acquisition geometry, temporal variability, MTF compensation, and GSD on spatial resolution were investigated.

Blonski, Slawomir↗