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At least 217 records · Page 12

First results from Spacelab 2

Preliminary results of physical experiments carried out during the Spacelab 2 Shuttle mission are summarized. Attention is given to experiments in the fields of plasma dynamics; solar physics; high-energy astrophysics; and astronomy. Plasma experiments included an ejectable plasma diagnosics package and measurements of the passive charging of the Shuttle vehicle in the surrounding space plasma. The solar physics instrument package consisted of a solar spectral irradiance monitor; a solar optical universal polarimeter (SOUP); and a solar helium abundance high-resolution telescope and spectrograph (HRTS). Astronomical observations were performed using a scanning infrared telescope (IRT) which consisted of a highly baffled herschelian telescope and 10 detectors covering wavelengths from 2 to 120 microns. Cosmic-ray nuclei were detected and analyzed using gas Cerenkov counters and a transition radiation detector. Addition experiments included a thin film fluid dynamics payload and analysis of blood samples taken from the mission specialists. Complete data records from the experiments have now been distributed for an analysis period which will take at least a year. A table listing the Spacelab 2 experiments and their principal investigators is provided.

Urban, E. W.↗

Are bars essential for starbursts in non-interacting galaxies

Analyzed here are the 1.6 and 2.2 micron images of a sample of galaxies that are classified as unbarred by the Revised Shapley-Ames Catalog. These galaxies have characteristic properties of nuclear starbursts and are examined through near infrared imaging in a search for hidden bars. Researchers selected a sample of 36 galaxies from the Revised Shapley-Ames Catalog that have far infrared luminosities greater than 10(exp 10) solar luminosity and hot Infrared Astronomy Satellite (IRAS) colors between 60 and 100 microns, indicative of nuclear starbursts, but are not classified as Seyfert 1 or 2. Their determination of the presence of a bar relies primarily on an analysis of the 2 micron image using the Galaxy Surface Photometry (GASP) package (Cawson, 1983). The GASP analysis programs determine the galaxy surface brightness and ellipticity profiles as well as the position angle and the center coordinates of the ellipses. To test the way that GASP will characterize the surface brightness of barred galaxies, two galaxies with known bars, NGC 1068 and NGC 2523, were imaged with the 2 micron camera and analyzed with GASP. Fifteen of the sample that are not clearly barred from optical data and are isolated were imaged at 1.6 and 2.2 microns; 9 of these do not appear to have bars. Strong bars therefore do not appear to be an absolute requirement for high infrared luminosity in isolated galaxies.

Pompea, Stephen M.↗

ARES Biennial Report 2012 Final

Since the return of the first lunar samples, what is now the Astromaterials Research and Exploration Science (ARES) Directorate has had curatorial responsibility for all NASA-held extraterrestrial materials. Originating during the Apollo Program (1960s), this capability at Johnson Space Center (JSC) included scientists who were responsible for the science planning and training of astronauts for lunar surface activities as well as experts in the analysis and preservation of the precious returned samples. Today, ARES conducts research in basic and applied space and planetary science, and its scientific staff represents a broad diversity of expertise in the physical sciences (physics, chemistry, geology, astronomy), mathematics, and engineering organized into three offices (figure 1): Astromaterials Research (KR), Astromaterials Acquisition and Curation (KT), and Human Exploration Science (KX). Scientists within the Astromaterials Acquisition and Curation Office preserve, protect, document, and distribute samples of the current astromaterials collections. Since the return of the first lunar samples, ARES has been assigned curatorial responsibility for all NASA-held extraterrestrial materials (Apollo lunar samples, Antarctic meteorites - some of which have been confirmed to have originated on the Moon and on Mars - cosmic dust, solar wind samples, comet and interstellar dust particles, and space-exposed hardware). The responsibilities of curation consist not only of the longterm care of the samples, but also the support and planning for future sample collection missions and research and technology to enable new sample types. Curation provides the foundation for research into the samples. The Lunar Sample Facility and other curation clean rooms, the data center, laboratories, and associated instrumentation are unique NASA resources that, together with our staff's fundamental understanding of the entire collection, provide a service to the external research community, which relies on access to the samples. The curation efforts are greatly enhanced by a strong group of planetary scientists who conduct peerreviewed astromaterials research. Astromaterials Research Office scientists conduct peer-reviewed research as Principal or Co-Investigators in planetary science (e. g., cosmochemistry, origins of solar systems, Mars fundamental research, planetary geology and geophysics) and participate as Co-Investigators or Participating Scientists in many of NASA's robotic planetary missions. Since the last report, ARES has achieved several noteworthy milestones, some of which are documented in detail in the sections that follow. Within the Human Exploration Science Office, ARES is a world leader in orbital debris research, modeling and monitoring the debris environment, designing debris shielding, and developing policy to control and mitigate the orbital debris population. ARES has aggressively pursued refinements in knowledge of the debris environment and the hazard it presents to spacecraft. Additionally, the ARES Image Science and Analysis Group has been recognized as world class as a result of the high quality of near-real-time analysis of ascent and on-orbit inspection imagery to identify debris shedding, anomalies, and associated potential damage during Space Shuttle missions. ARES Earth scientists manage and continuously update the database of astronaut photography that is predominantly from Shuttle and ISS missions, but also includes the results of 40 years of human spaceflight. The Crew Earth Observations Web site (http://eol.jsc.nasa.gov/Education/ESS/crew.htm) continues to receive several million hits per month. ARES scientists are also influencing decisions in the development of the next generation of human and robotic spacecraft and missions through laboratory tests on the optical qualities of materials for windows, micrometeoroid/orbital debris shielding technology, and analog activities to assess surface science operations. ARES serves as host to numerous students and visiting scientists as part of the services provided to the research community and conducts a robust education and outreach program. ARES scientists are recognized nationally and internationally by virtue of their success in publishing in peer-reviewed journals and winning competitive research proposals. ARES scientists have won every major award presented by the Meteoritical Society, including the Leonard Medal, the most prestigious award in planetary science and cosmochemistry; the Barringer Medal, recognizing outstanding work in the field of impact cratering; the Nier Prize for outstanding research by a young scientist; and several recipients of the Nininger Meteorite Award. One of our scientists received the Department of Defense (DoD) Joint Meritorious Civilian Service Award (the highest civilian honor given by the DoD). ARES has established numerous partnerships with other NASA Centers, universities, and national laboratories. ARES scientists serve as journal editors, members of advisory panels and review committees, and society officers, and several scientists have been elected as Fellows in their professional societies. This biennial report summarizes a subset of the accomplishments made by each of the ARES offices and highlights participation in ongoing human and robotic missions, development of new missions, and planning for future human and robotic exploration of the solar system beyond low Earth orbit.

Stansbery, Eileen↗

Ultrahigh resolution photographic films for X-ray/EUV/FUV astronomy

The quest for ultrahigh resolution full-disk images of the sun at soft X-ray/EUV/FUV wavelengths has increased the demand for photographic films with broad spectral sensitivity, high spatial resolution, and wide dynamic range. These requirements were made more stringent by the recent development of multilayer telescopes and coronagraphs capable of operating at normal incidence at soft X-ray/EUV wavelengths. Photographic films are the only detectors now available with the information storage capacity and dynamic range such as is required for recording images of the solar disk and corona simultaneously with sub arc second spatial resolution. During the Stanford/MSFC/LLNL Rocket X-Ray Spectroheliograph and Multi-Spectral Solar Telescope Array (MSSTA) programs, we utilized photographic films to obtain high resolution full-disk images of the sun at selected soft X-ray/EUV/FUV wavelengths. In order to calibrate our instrumentation for quantitative analysis of our solar data and to select the best emulsions and processing conditions for the MSSTA reflight, we recently tested several photographic films. These studies were carried out at the NIST SURF II synchrotron and the Stanford Synchrotron Radiation Laboratory. In this paper, we provide the results of those investigations.

Hoover, Richard B.↗

Type 2 radio bursts, interplanetary shocks and energetic particle events

Using the ISEE-3 radio astronomy experiment data 37 interplanetary (IP) type II bursts have been identified in the period September 1978 to December 1981. These events and the associated phenomena are listed. The events are preceded by intense, soft X ray events with long decay times (LDEs) and type II and/or type IV bursts at meter wavelengths. The meter wavelength type II bursts are usually intense and exhibit herringbone structure. The extension of the herringbone structure into the kilometer wavelength range results in the occurrence of a shock accelerated (SA) event. The majority of the interplanetary type II bursts are associated with energetic particle events. These results support other studies which indicate that energetic solar particles detected at 1 A.U. are generated by shock acceleration. From a preliminary analysis of the available data there appears to be a high correlation with white light coronal transients.

Cane, H. V.↗

Type II solar radio bursts, interplanetary shocks, and energetic particle events

Using the ISEE-3 radio astronomy experiment data 37 interplanetary (IP) type II bursts have been identified in the period September 1978 to December 1981. These events and the associated phenomena are listed. The events are preceded by intense, soft X ray events with long decay times (LDEs) and type II and/or type IV bursts at meter wavelengths. The meter wavelength type II bursts are usually intense and exhibit herringbone structure. The extension of the herringbone structure into the kilometer wavelength range results in the occurrence of a shock accelerated (SA) event. The majority of the interplanetary type II bursts are associated with energetic particle events. These results support other studies awhich indicate that energetic solar particles detected at 1 A.U. are generated by shock acceleration. From a preliminary analysis of the available data there appears to be a high correlation with white light coronal transients.

Cane, H. V.↗

Linear regression in astronomy. II

A wide variety of least-squares linear regression procedures used in observational astronomy, particularly investigations of the cosmic distance scale, are presented and discussed. The classes of linear models considered are (1) unweighted regression lines, with bootstrap and jackknife resampling; (2) regression solutions when measurement error, in one or both variables, dominates the scatter; (3) methods to apply a calibration line to new data; (4) truncated regression models, which apply to flux-limited data sets; and (5) censored regression models, which apply when nondetections are present. For the calibration problem we develop two new procedures: a formula for the intercept offset between two parallel data sets, which propagates slope errors from one regression to the other; and a generalization of the Working-Hotelling confidence bands to nonstandard least-squares lines. They can provide improved error analysis for Faber-Jackson, Tully-Fisher, and similar cosmic distance scale relations.

Feigelson, Eric D.↗

Asteroid team

The purpose of this task is to support asteroid research and the operation of an Asteroid Team within the Earth and Space Sciences Division at the Jet Propulsion Laboratory (JPL). The Asteroid Team carries out original research on asteroids in order to discover, better characterize and define asteroid properties. This information is needed for the planning and design of NASA asteroid flyby and rendezvous missions. The asteroid Team also provides scientific and technical advice to NASA and JPL on asteroid related programs. Work on asteroid classification continued and the discovery of two Earth-approaching M asteroids was published. In the asteroid photometry program researchers obtained N or Q photometry for more than 50 asteroids, including the two M-earth-crossers. Compositional analysis of infrared spectra (0.8 to 2.6 micrometer) of asteroids is continuing. Over the next year the work on asteroid classification and composition will continue with the analysis of the 60 reduced infrared spectra which we now have at hand. The radiometry program will continue with the reduction of the N and Q bandpass data for the 57 asteroids in order to obtain albedos and diameters. This year the emphasis will shift to IRAS follow-up observations; which includes objects not observed by IRAS and objects with poor or peculiar IRAS data. As in previous year, we plan to give top priority to any opportunities for observing near-Earth asteroids and the support (through radiometric lightcurve observations from the IRTF) of any stellar occultations by asteroids for which occultation observation expeditions are fielded. Support of preparing of IRAS data for publication and of D. Matson for his participation in the NASA Planetary Astronomy Management and Operations Working Group will continue.

Matson, D. L.↗

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↗

Semi-Supervised Novelty Detection with Adaptive Eigenbases, and Application to Radio Transients

We present a semi-supervised online method for novelty detection and evaluate its performance for radio astronomy time series data. Our approach uses adaptive eigenbases to combine 1) prior knowledge about uninteresting signals with 2) online estimation of the current data properties to enable highly sensitive and precise detection of novel signals. We apply the method to the problem of detecting fast transient radio anomalies and compare it to current alternative algorithms. Tests based on observations from the Parkes Multibeam Survey show both effective detection of interesting rare events and robustness to known false alarm anomalies.

anomaly detection↗

Development of doped-germanium photoconductors for astronomical observations at wavelengths from 30 to 120 micrometers

Technology was developed for production of doped-germanium detectors which have optimized performance in the 30- to 120-micrometer wavelength range and are capable of achieving the objectives of the Infrared Astronomy Satellite space mission. The work of this phase was divided into the following major tasks: (1) growth of Ge:Ga crystals from high-purity starting material with Ga concentrations different from that previously produced, and development of a zone leveling method to produce a uniform Ga doping concentration; (2) growth of uncompensated Ge:Be crystals from high-purity starting material with a range of Be concentrations between 10 to the 14th power and 10 to the 16th power atoms/cubic cm; (3) evaluation of crystals by means of Hall effect and resistance measurements as a function of temperature; (4) fabrication and test of detectors made from both Ge:Be and Ge:Ga crystals to determine the relative performance between different crystals. Correlation of detector test data with material evaluation data and analysis of how to further optimize detector performance.

Bratt, P. R.↗

Size-density relations in dark clouds: Non-LTE effects

One of the major goals of molecular astronomy has been to understand the physics and dynamics of dense interstellar clouds. Because the interpretation of observations of giant molecular clouds is complicated by their very complex structure and the dynamical effects of star formation, a number of studies have concentrated on dark clouds. Leung, Kutner and Mead (1982) (hereafter LKM) and Myers (1983), in studies of CO and NH3 emission, concluded that dark clouds exhibit significant correlations between linewidth and cloud radius of the form delta v varies as R(0.5) and between mean density and radius of the form n varies as R(-1), as originally suggested by Larson (1981). This result suggests that these objects are in virial equilibrium. However, the mean densities inferred from the CO data of LKM are based on an local thermodynamic equilibrium (LTE) analysis of their 13CO data. At the very low mean densities inferred by LKM for the larger clouds in their samples, the assumption of LTE becomes very questionable. As most of the range in R in the density-size correlation comes from the clouds observed in CO, it seems worthwhile to examine how non-LTE effects will influence the derived densities. One way to assess the validity of LTE-derived densities is to construct cloud models and then to interpret them in the same way as the observed data. Microturbulent models of inhomogeneous clouds of varying central concentration with the linewidth-size and mean density-size relations found by Myers show sub-thermal excitation of the 13CO line in the larger clouds, with the result that LTE analysis considerbly underestimates the actual column density. A more general approach which doesn't require detailed modeling of the clouds is to consider whether the observed T sub R*(13CO)/T sub R*(12CO) ratios in the clouds studied by LKM are in the range where the LTE-derived optical depths (and hence column densities) can be seriously in error due to sub-thermal excitation of the 13CO molecule.

Maloney, P.↗

The Membership and Distance of the Open Cluster Collinder 419

The young open cluster Collinder 419 surrounds the massive O star, HD 193322, that is itself a remarkable multiple star system containing at least four components. Here we present a discussion of the cluster distance based upon new spectral classifications of the brighter members, UBV photometry, and an analysis of astrometric and photometric data from the third U. S. Naval Observatory CCD Astrograph Catalog and Two Micron All Sky Survey Catalog. We determine an average cluster reddening of E(B - V) = 0.37 +/-.05 mag and a cluster distance of 741 plus or minus 36 pc. The cluster probably contains some very young stars that may include a reddened M3 III star, IRAS 20161+4035.

COLLINDER↗

Time series comparisons in Deep Space Network

The Deep Space Network (DSN) is NASA’s international array of antennas that support interplanetary spacecraft missions. DSN provides radar and radio astronomy observations that enhance our understanding of the solar system and the larger universe. A track is a block of continuous multi-dimensional time series from the beginning to end of DSN communication with the target spacecraft, containing 129 monitor data items lasting several hours at a frequency of 0.2-1Hz. Monitor data on each track reports on the performance of specific spacecraft operations and the DSN itself. DSN is receiving signals from 32 spacecraft across the solar system. DSN has pressure to reduce costs while maintaining the quality of support for DSN mission users. DSN operators need to simultaneously monitor multiple tracks and identify anomalies in real time. DSN has seen that as the number of missions increases, the data that needs to be processed increases over time. In this project, we look at the last 8 years of data for analysis. Any anomaly in the track indicates a problem with either the spacecraft, DSN equipment, or weather conditions. DSN operators typically write “discrepancy reports” for further analysis. It is recognized that it would be quite helpful to identify 10 similar historical tracks out of the huge database to quickly find/match anomalies. This tool has three functions: (1) identification of the top 10 similar historical tracks, (2) detection of anomalies compared to the reference normal track, and (3) comparison of statistical differences between two given tracks. The requirements for these features were confirmed by survey responses from 21 DSN operators and engineers. The preliminary machine learning model has shown promising performance (AUC=0.92). We plan to increase the number of data sets and perform additional testing to improve performance further before its planned integration into the Track Visualizer to assist DSN field operators and engineers.

Rebbapragada, Umaa↗

Millimeter-wave integrated-horn antennas. I - Theory. II - Experiment

Full-wave analysis is employed to determine the far-field pattern and input impedance of a dipole-fed horn antenna in a ground plane, and the theoretical results are compared with mm-wave and microwave data. The theoretical work exploits the Green's function corresponding to the horn structure and the method of moments. It is determined that the horn should have 70 sections/wavelength and 50 secondary modes for optimized accuracy, and certain dipole positions can reduce the resonance to zero. The experimentally derived impedance and radiation patterns agree with the constraints developed theoretically. The 70-degree flare-angle horn with selected dipole positions and horn apertures yields good radiation patterns, cross-polarization levels, and resonant dipole impedances. The conclusions are of interest to the development of the horn antennas etched in Si/GaAs for applications to zero-visibility tracking, radio astronomy, plasma diagnostics, and remote sensing.

Eleftheriades, George V.↗

Synchronization of clocks by very-long-baseline interferometry

Two hydrogen-maser clocks, one at Haystack Observatory and one at the National Radio Astronomy Observatory, were synchronized by means of observations of several extragalactic radio sources on March 28, and again on September 23, 1977. Observations were made sequentially in eight 360-kHz bands distributed between about 8.4 and 8.5 GHz with spacings designed to enable the group-delay difference between the signals received at the two observatories from a given source to be estimated unambiguously, within an uncertainty of less than 1 ns set by receiver noise. The epoch and the rate differences between the observatories' clocks for each experiment were estimated by analysis of observations that spanned several hours. The application of corrections for the contributions to the delays of the antennas, feeds, receiver systems, and recorders yielded absolute determinations of the clock epoch differences. During each experiment, portable cesium clocks were flown from the U.S. Naval Observatory to the observatories and back. The traveling-clock data, analyzed in each case after the VLBI synchronization had been completed, confirmed the VLBI results to within 18 and 14 ns for the first and second experiments, respectively.

Clark, T. A.↗

Compositional Analysis of Titan’s Atmosphere Using Spitzer Infrared Spectrograph Data

We present, for the first time, infrared spectra from the Spitzer Space Telescope’s Infrared Spectrograph (IRS) (2004-2008) of Titan in both the short wavelength-low resolution(SL, R=60~127,5.13-14.29 μm) and short wavelength-high resolution channels (SH, R=600, 9.89-19.51 μm) showing the emissions of CH4, C2H4, C2H2, C2H6, HCN, CO2, HC3N, C3H4, C4H2, and C3H8. Spitzer IRS data has been used to measure atmospheric composition of various Solar System bodies, including Neptune [1] and Uranus [2],[3]. Although Spitzer took multiple dedicated observations of Titan, none of the results have been modeled before. We conduct our own investigation of these datasets and search for new results. We retrieve temperature and gas composition profiles and compare the results obtained for Titan to those of the Cassini Composite Infrared Spectrometer (CIRS) and the Infrared Space Observatory Short Wavelength Spectrometer [4], and comment on the effect of spectral resolution on retrieved information content. We conclude by recommending gaps in current spectroscopic knowledge of molecular bands that could be addressed by theoretical and laboratory study to aid future astronomical studies of Titan, for example the James Webb Space Telescope (JWST) and the Stratospheric Observatory for Infrared Astronomy (SOFIA) Acknowledgments: Data analyzed in this project is public available online on the Spitzer Heritage Archive (sha.ipac.caltech.edu). This research has made use of the NASA/IPAC Infrared Science Archive, which is funded by the National Aeronautics and Space Administration and operated by the California Institute of Technology.

Titan↗

Research at Palomar Observatory in planetary astronomy

A wide range of observational studies are carried out to improve our understanding of the bodies of the outer solar system. Using the 200-inch Hale telescope, near-infrared observations are made of Uranus, Neptune, and the Pluto-Charon system. High time resolution occultation observations of the Uranus Ring system are used to study in detail the dynamics of this system. Occultation studies of Neptune are probing this intriguing ring-arc system. Occulation observations of the Pluto-Charon system probe the surface properties of these distant bodies. In addition, the plate material of the PSSII servey is being used to search for new comets and asteroids. Researchers observed one Neptune stellar occultation in July 1987 and completed the analysis of a series of seven separate Neptune occultation observations in conjunction with Nicholson et al., of Cornell. The analysis has shown that minimum of three ring arcs, at radii ranging from 54,000 km - 67,000 km are required to account for the high quality ring events. Current theoretical models can account for these data. Of two observations scheduled of Pluto-Charon mutual occulations scheduled for the 200-inch, the Charon eclipse event was successfully observed (the other was clouded out).

Soifer, B. T.↗