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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 433 records · Page 24
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NASA NTRS1994

Powerful model for the point source sky: Far-ultraviolet and enhanced midinfrared performance

I report further developments of the Wainscoat et al. (1992) model originally created for the point source infrared sky. The already detailed and realistic representation of the Galaxy (disk, spiral arms and local spur, molecular ring, bulge, spheroid) has been improved, guided by CO surveys of local molecular clouds, and by the inclusion of a component to represent Gould's Belt. The newest version of the model is very well validated by Infrared Astronomy Satellite (IRAS) source counts. A major new aspect is the extension of the same model down to the far ultraviolet. I compare predicted and observed far-utraviolet source counts from the Apollo 16 'S201' experiment (1400 A) and the TD1 satellite (for the 1565 A band).

Cohen, Martin↗
NASA NTRS1994

Comparison of large-scale structures and velocities in the local universe

Comparison of the large-scale density and velocity fields in the local universe shows detailed agreement, strengthening the standard paradigm of the gravitational origin of these structures. Quantitative analysis can determine the cosmological density parameter, Omega, and biasing factor, b; there is virtually no sensitivity in any local analyses to the cosmologial constant, lambda. Comparison of the dipole anisotropy of the cosmic microwave background with the acceleration due to the Infrared Astronomy Satellite (IRAS) galaxies puts the linear growth factor in the range beta approximately equals Omega (exp 0.6)/b = 0.6(+0.7/-0.3) (95% confidence). A direct comparison of the density and velocity fields of nearby galaxies gives beta = 1.3 (+0.7/-0.6), and from nonlinear analysis the weaker limit (Omega greater than 0.45 for b greater than 0.5 (again 95% confidence). A tighter limit (Omega greater than 0.3 (4-6 sigma)), is obtained by a reconstruction of the probability distribution function of the initial fluctuations from which the structures observed today arose. The last two methods depend critically on the smooth velocity field determined from the observed velocities of nearby galaxies by the POTENT method. A new analysis of these velocities, with more than three times the data used to obtain the above quoted results, is now underway and promises to tighten the uncertainties considerably, as well as reduce systematic bias.

Yahil, Amos↗
NASA NTRS1994

Stellar-based calibration in the far infrared with application to IRAS Band 4

Because stars emit very small portions of their outputs in the far infrared, using them as calibrators requires precise measurement and correction for filter leaks at shorter wavelengths. Therefore, it is common to base far infrared calibrations on planetary objects such as asteriods. However, asteroids are complex geological bodies whose thermal properties depend on their evolutionary histories as well as on their gross parameters such as mass and composition, making them difficult to model as calibrators. We propose a new method for measuring filter leaks that can be carried out using the end-to-end detector system and therefore allows reliable use of stellar calibrators. We illustrate this method by showing that the Infrared Astronomy Satellite (IRAS) 100 micrometers (Band 4) filters had a short wavelength leak of 14.3% +/- 3.6% on stars similar to alpha Boo, but that there is no detectable leak in the 60 micrometers (Band 3) filters. We derive a calibration for Band 4 from stellar colors in a way that is closely analogous to the calibrations of Bands 1, 2, and 3. With correction for the leak, the stellar-based calibration is virtually identical to the original calibration based on asteroids; this result requires that the spectra of the asteriods for the original calibration differ from greybody behavior between 60 and 100 micrometers by about 10%.

Kirby, D. J.↗
NASA NTRS1994

Extended 60 micrometers emission from nearby Mira variables

The Infrared Astronomy Satellite (IRAS) has detected extended emission around a number of evolved stars. Individual IRAS scans of nearby Mira variables which showed emission from circumstellar dust and for which distance estimates were available were examined. Extended emission at 60 micrometers was detected for R Cas, o Cet, R Leo, U Ori, and possibly for R Hor. The Leung code for the calculation of radiative transfer in a circumstellar dust shell was used to calculate the emission from model dust shells composed of silicate grains. The output was convolved with the IRAS beam profile to determine whether steady mass loss could explain the observed extension. The observed extensions for o Cet, R Hor and U Ori could be due to steady mass loss, while the model calculations do not produce enough extension to explain the observations of R Cas and R Leo.

Bauer, Wendy Hagen↗
NASA NTRS1994

A 5 GHz VLA survey of the galactic plane

We have used the Very Large Array (VLA) to survey the inner Galaxy (absolute value of b less than 0.4 deg, l = 350-40 deg) at 5 GHz to a limiting sensitivity of between 2.5 and 10 mJy. The survey has resulted in a catalog of 1272 discrete sources (including 100 sources outside the formal survey area) of which we have temtatively identified approximately 450 as ultracompact H II regions and approximately 45 as planetary nebulae. Approximately 30% of the radio sources are detected in the Infrared Astronomy Satellite (IRAS) Point source Catalog. The results confirm a scale height of only 30 pc for ultracompact H II regions. We show that source lists generated from the IRAS Point Source Catalog alone suffer serious selection effects; the combination of the IRAS and radio surveys allows us to produce a much more complete census of the regions of massive star formation in our Galaxy.

Becker, Robert H.↗
NASA NTRS1993

The SIRTF mission

This paper describes the status of NASA's Space Infrared Telescope Facility (SIRTF) program. SIRTF will be a cryogenically cooled observatory for infrared astronomy from space and is planned for launch early in the next decade. We discuss a newly modified baseline SIRTF mission and review the state of the detector technology which will provide the heart of SIRTF's scientific advances.

Werner, M. W.↗
NASA NTRS1995

Space Studies Board, 1994

This 1994 report of the Space Studies Board of the National Research Council summarizes the charter and organization of the board, activities and membership, major and short reports, and congressional testimony. A cumulative bibliography of the Space Studies (formerly Space Science) Board and its committees is provided. An appendix contains reports of the panel to review Earth Observing System Data and Information System (EOSDIS) plans. Major reports cover scientific opportunities in the human exploration of space, the dichotomy between funding and effectiveness in space physics, an integrated strategy for the planetary sciences for the years 1995-2010, and Office of Naval Research (ONR) research opportunities in upper atmospheric sciences. Short reports cover utilization of the space station, life and microgravity sciences and the space station program, Space Infrared Telescope Facility and the Stratospheric Observatory for Infrared Astronomy, and the Advanced X-ray Astrophysics Facility and Cassini Saturn Probe.

Source record↗
NASA NTRS1995

Flight opportunities for science teacher enrichment

NASA Astrophysics Division supports a pre-college teacher program to provide Flight Opportunities for Science Teacher EnRichment (FOSTER). To date, forty-five teachers are participating, and the program will expand nation-wide to serve fifty teachers per year on board the Kuiper Airborne Observatory. In the future, the Stratospheric Observatory for Infrared Astronomy (SOFIA) will bring more than one-hundred teachers per year on board for astronomical research mission. FOSTER is supported by a grant to the SETI Institute from the NASA Astrophysics Division, NAGW-3291.

Devore, Edna↗
NASA NTRS1991

The relation between FIR and H I emission in galaxies

This project explored the relationship between the global far-infrared and neutral hydrogen (H I) emission from galaxies, based on data from the Infrared Astronomy Satellite (IRAS) and published radio data. 100 and 60 micron IRAS fluxes were used to establish a temperature corrected measure of the cold dust emission, and H I fluxes were drawn from the literature with the greatest possible consistency. The degree of correlation between the FIR and H I fluxes was found to be better than in previous studies, comparable to the correlation previously found between FIR and CO fluxes. The improvement was obtained largely by (1) separating 'stripped' from 'unstripped' galaxies, and (2) using compatible sources of H I data. Stripping occurs in clusters of galaxies and is probably caused by ram-pressure effects as a galaxy travels through the intergalactic medium. Our results suggest that stripped galaxies have had their outer-disk gas removed (approximately 80% of their total H I) while retaining most of their 100-micron-emitting dust. This strongly shifts the ratio of their 100-micron-to-H I fluxes. The second problem, arising from diverse sources of data, arises because differing telescopes and observational techniques give rise to substantial disagreement in the measured H I flux, and this degrades the correlation of the FIR and H I fluxes.

Schneider, Stephen E.↗
NASA NTRS1995

Flowfield and acoustic characteristics of telescope cavity in SOFIA platform

Unsteady three-dimensional flowfields are calculated for the Stratospheric Observatory For Infrared Astronomy (SOFIA) at both free-flight cruise and wind tunnel conditions with a view to help in the design process of an acoustically quiet telescope cavity and to understand the flow physics of a three dimensional cavity. The calculation method is based on the numerical solution of thin layer Navier-Stokes equations on a Chimera overset grid system. The Boeing 747-200 aircraft is examined as one option for the SOFIA platform. The flowfield domain is composed of 45 grids consisting of over 4.1 million points. Numerical simulations are performed for both wind tunnel and free-flight cruise conditions at one freestream condition of M(infinity) = 0.85, alpha = 2.5 deg. Comparison of results from wind tunnel simulation show good agreement with experimental data for time-averaged surface pressures, drag for the empennage, and sound pressure levels and power spectra at various locations within the cavity and on the telescope. The presence of the open cavity induces an incremental drag increase, an increased acoustic radiation, and an increase in unsteady pressure loads on the telescope. Its impact on the effectiveness of aircraft control surfaces appears minimal.

Srinivasan, G. R.↗
NASA NTRS1995

Space Studies Board Annual Report 1994

The following summaries of major reports are presented: (1) 'Scientific Opportunities in the Human Exploration of Space;' (2) 'A Space Physics Paradox;' (3) 'An Integrated Strategy for the Planetary Sciences;' and (4) 'ONR (Office of Naval Research) Research Opportunities in Upper Atmospheric Sciences.' Short reports on the following topics are also presented: life and microgravity sciences and the Space Station Program, the Space Infrared Telescope Facility and the Stratospheric Observatory for infrared astronomy, the Advanced X-ray Astrophysics Facility and Cassini Saturn Probe, and the utilization of the Space Station.

Source record↗
NASA NTRS1996

Design considerations for AIRES, an airborne infrared echelle spectrometer for SOFIA

The airborne infrared echelle spectrometer (AIRES) was proposed as a facility instrument for the stratospheric observatory for infrared astronomy (SOFIA) project. The preliminary AIRES design uses multiple two dimensional detector arrays and a 1.2 m long, 76 deg blaze angle echelle to combine high spectral resolution with diffraction limited imaging in the cross-dispersion direction. A preliminary optical design and the mechanical architecture are presented together with the analysis and prototyping of lightweight aluminum echelles. Instrument efficiencies are calculated and compared for different gratings, and the associated mechanical design tradeoffs are discussed.

Haas, Michael R.↗
NASA NTRS1995

Theoretical Studies of Dust in the Galactic Environment: Some Recent Advances

Dust grains, although a minor constituent, play a very important role in the thermodynamics and evolution of many astronomical objects, e.g., young and evolved stars, nebulae, interstellar clouds, and nuclei of some galaxies. Since the birth of infrared astronomy over two decades ago, significant progress has been made not only in the observations of galactic dust, but also in the theoretical studies of phenomena involving dust grains. Models with increasing degree of sophistication and physical realism (in terms of grain properties, dust formation, emission processes, and grain alignment mechanisms) have become available. Here I review recent progress made in the following areas: (1) Extinction and emission of fractal grains. (2) Dust formation in radiation-driven outflows of evolved stars. (3) Transient heating and emission of very small dust grains. Where appropriate, relevant modeling results are presented and observational implications emphasized.

Leung, Chun Ming↗
NASA NTRS1997

Science in the Stratosphere

The Science in the Stratosphere program, first established in 1992, was conceived to introduce K-6 teachers to airborne infrared astronomy through the Kuiper Airborne Observatory (KAO), and to use this venue as a basis for seeing scientists at work in a mission-intensive program. The teachers selected for this program would bring their new perspectives back to their schools and students. Unlike the related FOSTER program, the emphasis of this program was on more intensive exposure of the KAO mission to a small number of teachers. The teachers in the Science in the Stratosphere program essentially lived with the project scientists and staff for almost a week. One related goal was to imbed the KAO project with perspectives of working teachers, thereby sensitizing the project staff and scientists to educational outreach efforts in general, which is an important goal of the NASA airborne astronomy program. A second related goal was to explore the ways in which K-5 educators could participate in airborne astronomy missions. Also unlike FOSTER, the Science in the Stratosphere program was intentionally relatively unstructured, in that the teacher participants were wholly embraced by the science team, and were encouraged to 'sniff out' the flavor of the whole facility by talking with people.

Lester, Dan↗
NASA NTRS1998

WIRE, SOFIA and SIRTF

WIRE, SOFIA and SIRTF are three planned NASA missions for infrared astronomy. Each will make significant contributions to the study of exo-zodiacal dust, planetary debris disks, and/or the zodiacal material within our own solar system. These missions and their measurement and scientific capabilities are synopsized. The principal contribution of these missions to this field of study will be to establish and strengthen its intellectual foundations rather than to pinpoint specific targets for planetary searches. This is consistent with their relatively near-term availability. Moreover, this intellectual understanding can assure that subsequent missions approach this subject from a sound scientific perspective which will yield valuable results independent of the success of a particular planet finding strategy. Each of these missions - most urgently WIRE with its Fall, 1998 launch date - would make good use of a list of candidate target stars for exo-zodiacal/planet-finding studies. The preparation of such a list was one of the recommendations of the exo-zodiacal workshop.

Werner, Michael↗
NASA NTRS1997

A study of the evolutionary stages of IRAS sources and outflows in the Mon OB1 dark cloud

An ongoing project aiming to relate the evolutionary stages of the Infrared Astronomy Satellite (IRAS) sources in the Mon OB1 dark cloud to the morphology and energetics of outflows associated with some of these sources, is reported on. Previous evolutionary classifications of IRAS sources are refined and potential class O objects are identified. The fully-sampled CO maps of the outflows in this cloud are presented. These observations yield information on outflow structure, kinematics and excitation conditions. Low-intensity, high velocity gas is observed in the youngest outflows. This emission is characterized by relatively flat line wings at the highest velocities in spectral line profiles obtained at the peaks of the outflow emission.

Wolf-Chase, G.↗
NASA NTRS1997

Sofia Science Working Group

The purpose of this grant was to enable the Principal Investigator (P.I.) to travel to and participate in the meetings and activities of the NASA SOFIA Science Working Group (SSWG), and to spend time working on some of the associated technical issues relating to the SOFIA (Stratospheric Observatory for Infrared Astronomy) project. The SOFIA Science Working Group was established to help develop the plans and specifications for the next-generation airborne observatory ("SOFIA"), which is now under development. The P.I. was asked to serve on the SSWG due to his experience in airborne astronomy: he has developed several astronomical instruments for the Kuiper Airborne Observatory NASA's previous airborne astronomy platform (which was decommissioned in 1995 in preparation for SOFIA). SOFIA, which will be a 747 SP aircraft carrying a 2.7 meter diameter telescope, is a joint project sponsored by NASA and DLR (the German space agency), and is now under development by a consortium including Universities Space Research Association (USRA), Raytheon, Sterling Software, and United Airlines. Further details on the SOFIA project can be found on the internet at http: //sofia. arc. nasa. gov. Rather than develop the SOFIA observatory in-house, NASA decided to privatize the project by issuing a Request for Proposals (RFP). The respondents to this RFP were consortia of private organizations which together had the required facilities and expertise to be able to carry out the project; the winner was the group led by USRA. One of the main roles of the SSWG was to help develop the technical specifications for the SOFIA observatory. In particular, the SSWG provided advice to NASA on the specifications that were written into the RFP, particularly those which had an important impact on the scientific productivity of the observatory. These specifications were discussed at the meetings of the SSWG, which were held primarily at NASA/Ames (in California) and at NASA Headquarters (in Washington DC). Apart from these meetings, members of the SSWG were expected to perform more detailed analyses of the impact of certain parameters and specifications on the performance of astronomical instruments. The SSWG ended its activities with the selection of the USRA team in January 1997.

Zmuidzinas, J.↗
NASA NTRS1999

Global Studies of Molecular Clouds in the Galaxy, The Magellanic Clouds, and M31

Over the course of this grant we used various spacecraft surveys of the Galaxy and M31 in conjunction with our extensive CO spectral line surveys to address central problems in galactic structure and the astrophysics of molecular clouds. These problems included the nature of the molecular ring and its relation to the spiral arms and central bar, the cosmic ray distribution, the origin of the diffuse X-ray background, the distribution and properties of x-ray sources and supernova remnants, and the Galactic stellar mass distribution. For many of these problems, the nearby spiral M31 provided an important complementary perspective. Our CO surveys of GMCs (Galactic Molecular Clouds) were crucial for interpreting Galactic continuum surveys from satellites such as GRO (Gamma Ray Observatory), ROSAT (Roentgen Satellite), IRAS (Infrared Astronomy Satellite), and COBE (Cosmic Background Explorer Satellite) because they provided the missing dimension of velocity or kinematic distance. GMCs are a well-defined and widespread population of objects whose velocities we could readily measure throughout the Galaxy. Through various emission and absorption mechanisms involving their gas, dust, or associated Population I objects, GMCs modulate the galactic emission in virtually every major wavelength band. Furthermore, the visibility. of GMCs at so many wavelengths provided various methods of resolving the kinematic distance ambiguity for these objects in the inner Galaxy. Summaries of our accomplishments in each of the major wavelength bands discussed in our original proposal are given

Thaddeus, Patrick↗