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NASA NTRS1995

Hybrid superconductor magnet bearings

Hybrid superconductor magnet bearings (HSMB's) utilize high temperature superconductors (HTS's) together with permanent magnets to form a frictionless interface between relatively rotating parts. They are low mass, stable, and do not incur expenditure of energy during normal operation. There is no direct physical contact between rotor and stator, and hence there is no wear and tear. However, just as any other applications of HTS's, it requires a very cold temperature to function. Whereas this might be perceived as a disadvantage on earth, it is of no great concern in space or on the moon. To astronomers, the moon is an excellent site for an observatory, but the cold and dusty vacuum environment on the moon precludes the use of mechanical bearings on the telescope mounts. Furthermore, drive mechanisms with very fine steps, and hence bearings with extremely low friction are needed to track a star from the moon, because the moon rotates very slowly. All aspects considered, the HSMB is about the only candidate that fits in naturally. Here, we present a design for one such bearing, capable of supporting a telescope that weighs about 3 lbs on Earth.

Chu, Wei-Kan↗

NASA NTRS1985

Capabilities of the LDEF-2 heavy nuclei collection

To take the next big step beyond High Energy Astronomy Observatory (HEAO-3) the Heavy Nuclei Collector (HNC), to be carried on an LDEF reflight, has the goals of greatly increased collecting power ( 30 actinides) and charge resolution sigma sub Z or = 0.25 E for Z up to approximately 100, which will provide abundances of all the charges 40 or Z or = 96 and permit sensitive searches for hypothetical particles such as monopoles, superheavy elements, and quark nuggets.

Drach, J.↗

NASA NTRS2000

Future Missions for Gamma-Ray Astronomy

Gamma-ray astronomy has made great advances in recent years, due largely to the recently completed 9-year mission of the Compton Gamma Ray Observatory. In this talk I will give an overview of what advances we may expect in the near future, with particular emphasis on earth-orbiting missions scheduled for flight within the next 5 years. Two missions, the High Energy Transient Explorer and Swift, will provide important new information on the sources of gamma-ray bursts. The Gamma-Ray Large Area Space Telescope will investigate high energy emission from a wide variety of sources, including active galaxies and gamma-ray pulsars. The contributions of ground-based and multiwavelength observations will also be addressed.

Meegan, Charles↗

NASA NTRS1982

Concepts for large interferometers in space

Very high angular resolution can be achieved in optical and radio astronomy through interferometers in space. Evolutionary approaches and required technological advances are presented. In the optical region a phase-coherent array, (COSMIC) starting as a four-element linear array is discussed. Combining several modules results in greatly improved resolution with a goal of combining images to obtain a single field of view with 0.004 arcsecond resolution. The angular resolution, detail and temporal coverage of radio maps obtained by ground-based Very Long Interferometry (VLBI) can be greatly improved by placing one of the stations in earth orbit. An evolutionary program leading to a large aperture VLBI observatory in space is discussed.

Morgan, S. H.↗

NASA NTRS1983

Use of Space Station for Earth and Planetary Exploration

The Earth and Planetary Exploration program attempts to develop an understanding of the earth as a planet by utilizing the capability of instruments in space to explore the earth. Studies of the solar system are conducted to gain an understanding of its origin and evolution. The facilities for planetary observations will be greatly extended by making use of a Space Station. Special demands related to the appropriate utilization of a Space Station observatory are discussed, taking into account the employment of ultraviolet spectroscopy for the study of planetary atmospheres and comets, advantages provided by infrared spectroscopy, far-infrared and submillimeter spectroscopy and radiometery, and the search for other planetary systems. The capabilities provided by the Space Station for an investigation of earth resources are explored. Attention is given to vegetation research and observations, land cover dynamics, hydrologic cycle research, geological research, suitable instruments, and a study of crustal dynamics.

Piotrowski, W. L.↗

NASA NTRS1994

SLR tracking of GPS-35

An experiment was designed to launch a corner cube retroreflector array on one of the Global Positioning Satellites (GPS). The launch on Aug. 31, 1993 ushered in the era of SLR tracking of GPS spacecraft. Once the space operations group finished the check-out procedures for the new satellite, the agreed upon SLR sites were allowed to track it. The first site to acquire GPS-35 was the Russian system at Maidanak and closely after the MLRS system at McDonald Observatory, Texas. The laser tracking network is currently tracking the GPS spacecraft known as GPS-35 or PRN 5 with great success. From the NASA side there are five stations that contribute data regularly and nearly as many from the international partners. Upcoming modifications to the ground receivers will allow for a further increase in the tracking capabilities of several additional sites and add some desperately needed southern hemisphere tracking. We are analyzing the data and are comparing SLR-derived orbits to those determined on the basis of GPS radiometric data.

Pavlis, Erricos C.↗

NASA NTRS1994

A review of recent results in gamma-ray astronomy obtained from high-altitude balloons

This paper reviews recent results in gamma-ray astronomy obtained from experiments flown on high-altitude balloons. New generation balloon-borne imaging experiments have produced the first gamma-ray maps of the Galactic center (GC) region. Balloon flights of new gamma-ray spectrometers with improved sensitivity have provided important new information on the GC annihilation line. For the first time, the narrow 511 keV line as been resolved (FWHM approx. = 3 keV). A very interesting spectral feature at approximately 170 keV has been attributed to backscattered annihilation, probably from the vicinity of a compact object. New results from the Compton Gamma-Ray Observatory (CGRO)/OSSE and Granat/SIGMA experiments on the annihilation line, when considered together with the recent balloon results, have added greatly to our knowledge and understanding of the origin and distribution of this emission. Balloon-borne instruments have made important measurements of gamma-ray continuum and line emission from SN 1987A. The GRIS spectrometer unambiguously resolved the 847 and 1238 keV line emission from radioactive Co-56 synthesized during the explosion. This data indicated that simple spherically symmetric and homogeneous models did not provide an adequate description of the expanding SN shell.

Teegarden, B. J.↗

NASA NTRS1974

Ultraviolet television data from the orbiting astronomical observatory. II - Stellar ultraviolet colors and interstellar extinction

The results from the Celescope Catalog of Ultraviolet Stellar Observations (Davis, Deutschman, and Haramundanis 1973) are studied, emphasizing statistical groups and subgroups of stars. In spite of the rather large observational errors, the great number of Celescope observations make it possible to do that kind of study with reasonable accuracy. Some stars have ultraviolet colors that differ significantly from those of the group to which they have been assigned on the basis of ground-based observations. An attempt is made to describe the general properties of the ultraviolet colors of the stars as observed by the Celescope experiment on board NASA's Orbiting Astronomical Observatory (OAO-2). Besides the direct applicability of these results to the general study of stellar atmospheres and of interstellar extinction, they are also considered as a frame of reference for further studies of individual stars and groups of stars.

Peytremann, E.↗

NASA NTRS1998

Summary of Research on Research Award

During this grant period, we analyzed data obtained with the Kuiper Airborne Observatory. The goal of the research was to study the distribution of matter around very young stars. These studies resulted in greatly improved understanding of the environment in which stars form. In particular, we studied regions forming stars of intermediate mass. In the process of studying these regions, we found that the models of collapse of low mass stars did a good job of explaining our observations of those regions, but that the dust around more massive stars was distributed in different ways, usually less centrally condensed. We have submitted for publication a large paper, in which all our observations of intermediate mass star-forming regions are presented and analyzed. This paper will provide a valuable reference and will be the basis for future modeling of these sources, using codes that we have developed. In addition to direct studies of the dust, we have used the information from our studies of the dust to make more realistic models of the emission from molecules in star forming regions. In particular, we were able to dispense with ad hoc ideas about the temperature and put in temperature distributions determined from the modeling of the far-infrared observations.

Evans, Neal J., II↗

NASA NTRS2009

Better Spectrometers, Beautiful Spectra and Confusion for All

The confluence of enormous improvements in submillimeter receivers and the development of powerful large scale observatories is about to force astrophysics and the sciences that support it to develop novel approaches for interpretation of data. The historical method of observing one or two lines and carefully analyzing them in the context of a simple model is now only applicable for distant objects where only a few lines are strong enough to be observable. Modern observatories collect many GHz of high signal-to-noise spectra in a single observation and in many cases, at sufficiently high spatial resolution to start resolving chemically distinct regions. The observatories planned for the near future and the inevitable upgrades of existing facilities will make large spectral data sets the rule rather than the exception in many areas of molecular astrophysics. The methodology and organization required to fully extract the available information and interpret these beautiful spectra represents a challenge to submillimeter astrophysics similar in magnitude to the last few decades of effort in improving receivers. The quality and abundance of spectra effectively prevents line-by-line analysis from being a time efficient proposition, however, global analysis of complex spectra is a science in its infancy. Spectroscopy at several other wavelengths have developed a number of techniques to analyze complex spectra, which can provide a great deal of guidance to the molecular astrophysics community on how to attack the complex spectrum problem. Ultimately, the challenge is one of organization, similar to building observatories, requiring teams of specialists combining their knowledge of dynamical, structural, chemical and radiative models with detailed knowledge in molecular physics and gas and grain surface chemistry to extract and exploit the enormous information content of complex spectra. This paper presents a spectroscopists view of the necessary elements in a tool for complex spectral analysis.

Spectral Analysis↗

NASA NTRS1985

The great flare of 1982 June 6

The great soft X-ray (SXR) flare (X12) of the past solar maximum was observed by Hinotori and by Big Bear Solar Observatory (BBSO) on June 6, 1982. Hinotori data consist of hard X-ray (HXR) and SXR images in the rise and decay of the flare, high-resolution soft X-ray spectra throughout the flare, and HXR and gamma-ray data. The BBSO data include films of H-alpha, H-alpha blue wing, D3 and longitudinal magnetic field, as well as video tapes of continuum. Images in HXR, SXR, H-alpha, D3 and the continuum are compared and SXR spectra analyzed. The flare resulted from extended motion of a large spot shearing the magnetic field. D3 and white-light images exhibit a progression from fast flashes to two ribbons, while both HXR and SXR are centered on the optical kernels. The continuum emission shows the same temporal behavior as the HXR at 160 keV. In its early phases, the Fe XXV line was double-peaked, and a decreasing blueshifted (up to 400 km/sec) component was observed, from which the evaporation rate of chromospheric material was estimated. It is suggested that this upflow is adequate to supply the coronal cloud. Flare energetics are discussed in detail, and it is concluded that a significant amount of energy was deposited in the corona, and that nonthermal electrons are the major energy input.

Tanaka, K.↗

NASA NTRS2017

Solar Magnetic Activity and Solar-Stellar Connections

Prediction of solar magnetic activity on various temporal scales is a fundamental element of space weather, which requires a wide range of theoretical and observational expertise in solar phenomena from the deep interior to the corona. Historical observations have revealed many features of cyclic variations of the solar activity; but these data are dramatically insufficient to draw a physical picture of global magnetic field evolution. New observational data, currently available from space missions and ground-based observatories, provide us with detailed information about solar dynamics and magnetism. However, because of the relatively short duration of data series and the great variety of data types and quality, it is challenging to assimilate these data in theoretical models and make reliable forecasts. The recent unexpectedly weak solar activity cycles, as well as observations of rotational and magnetic topology transitions in solar-type stars, suggest that the Sun and its magnetic dynamo are currently in a very interesting evolutionary stage. This could relate to the difficulty in getting a model of the Sun to produce solar-like – rather than anti-solar-like – differential rotation, to reproduce the rotation profile obtained from helioseismology, and to predict solar activity cycles.

magnetic↗

NASA NTRS1993

A computer-controlled x-y offset guiding stage for the MLRS

The MLRS has experienced excellent success in its lunar and artificial satellite laser ranging operations during its many years of operation, in spite of its relatively small 'receive' aperture. We continue to strive, however, for a greater volume of data, together with better accuracy and precision. We have just now completed the design, construction, and implementation of a computer controlled x-y offset guiding stage for the MLRS, analogous to the manual one that had been a part of the original 2.7-m lunar laser ranging system on Mt. Locke at McDonald Observatory. In the past, we had been hampered by the lack of a satisfactory hardware design which could fit within the very cramped quarters of the MLRS telescope's tail piece. Recently, with funding support from the U.S. Naval Observatory and the design and construction expertise of DFM Engineering, Inc., a satisfactory instrument has been specified, designed, built, and installed. This instrument will greatly expand MLRS observational opportunities by allowing the observing crews to actively guide on visible off axis lunar surface features or background stars while the on-axis lunar surface retroreflector targets are in the dark. This paper describes this instrument and its present implementation at the MLRS.

Shelus, Peter J.↗

NASA NTRS2014

Chromospheric Variability: Analysis of 36 years of Time Series from the National Solar Observatory/Sacramento Peak Ca II K-line Monitoring Program

Analysis of more than 36 years of time series of seven parameters measured in the NSO/AFRL/Sac Peak K-line monitoring program elucidates five elucidates five components of the variation: (1) the solar cycle (period approx. 11 years), (2) quasi-periodic variations (periods approx 100 days), (3) a broad band stochastic process (wide range of periods), (4) rotational modulation, and (5) random observational errors. Correlation and power spectrum analyses elucidate periodic and aperiodic variation of the chromospheric parameters. Time-frequency analysis illuminates periodic and quasi periodic signals, details of frequency modulation due to differential rotation, and in particular elucidates the rather complex harmonic structure (1) and (2) at time scales in the range approx 0.1 - 10 years. These results using only full-disk data further suggest that similar analyses will be useful at detecting and characterizing differential rotation in stars from stellar light-curves such as those being produced by NASA's Kepler observatory. Component (3) consists of variations over a range of timescales, in the manner of a 1/f random noise process. A timedependent Wilson-Bappu effect appears to be present in the solar cycle variations (1), but not in the stochastic process (3). Component (4) characterizes differential rotation of the active regions, and (5) is of course not characteristic of solar variability, but the fact that the observational errors are quite small greatly facilitates the analysis of the other components. The recent data suggest that the current cycle is starting late and may be relatively weak. The data analyzed in this paper can be found at the National Solar Observatory web site http://nsosp.nso.edu/cak_mon/, or by file transfer protocol at ftp://ftp.nso.edu/idl/cak.parameters.

Solar physics↗

NASA NTRS2017

The Formation and Maintenance of the Dominant Southern Polar Crown Cavity of Cycle 24

In this article, we report a study of the longest-lived polar crown cavity of Solar Cycle 24, using an observation from 2013, and propose a physical mechanism to explain its sustained existence. We used high temporal and spatial resolution observations from the Atmospheric Imaging Assembly (AIA) and the Helioseismic Magnetic Imager (HMI) instruments on board the Solar Dynamics Observatory (SDO) to explore the structure and evolution of the cavity. Although it existed for more than a year, we examined the circumpolar cavity in great detail from 2013 March 21 to 2013 October 31. Our study reinforces the existing theory of formation of polar crown filaments that involves two basic processes to form any polar crown cavity as well as the long-lived cavity that we studied here. First, the underlying polarity inversion line (PIL) of the circumpolar cavity is formed between (1) the trailing part of dozens of decayed active regions distributed in different longitudes and (2) the unipolar magnetic field in the polar coronal hole. Second, the long life of the cavity is sustained by the continuing flux cancellation along the PIL. The flux is persistently transported toward the polar region through surface meridional flow and diffusion. The continuing flux cancellation leads to the shrinking of the polar coronal hole.

Karna, N.↗

NASA NTRS1990

Lunar astronomical observatories - Design studies

The best location in the inner solar system for the grand observatories of the 21st century may be the moon. A multidisciplinary team including university students and faculty in engineering, astronomy, physics, and geology, and engineers from industry is investigating the moon as a site for astronomical observatories and is doing conceptual and preliminary designs for these future observatories. Studies encompass lunar facilities for radio astronomy and astronomy at optical, ultraviolet, and infrared wavelengths of the electromagnetic spectrum. Although there are significant engineering challenges in design and construction on the moon, the rewards for astronomy can be great, such as detection and study of earth-like planets orbiting nearby stars, and the task for engineers promises to stimulate advances in analysis and design, materials and structures, automation and robotics, foundations, and controls. Fabricating structures in the reduced-gravity environment of the moon will be easier than in the zero-gravity environment of earth orbit, as Apollo and space-shuttle missions have revealed. Construction of observatories on the moon can be adapted from techniques developed on the earth, with the advantage that the moon's weaker gravitational pull makes it possible to build larger devices than are practical on earth.

Johnson, Stewart W.↗

NASA NTRS1993

The Einstein Observatory catalog of IPC x ray sources. Volume 4E: Right ascension range 08h 00m to 11h 59m

The Einstein Observatory (HEAO-2, launched November 13, 1978) achieved radically improved sensitivity over previous x-ray missions through the use of focusing optics which simultaneously afforded greatly reduced background and produced true images. During its 2.5-yr mission, the Einstein X-Ray Telescope was pointed toward some 5,000 celestial targets, most of which were detected, and discovered several thousand additional 'serendipitous' sources in the observed fields. This catalog contains contour diagrams and source data, obtained with the imaging proportional counter in the 0.16 to 3.5 keV energy band, and describes methods for recovering upper limits for any sky position within the observed images, The main catalog consists of six volumes (numbered 2 through 7) of right ascension ordered pages, each containing data for one observation. Along with the primary documentaion describing how the catalog was constructed, volume 1 contains a complete source list, results for merged fields, a reference system to published papers, and data useful for calculating upper limits and fluxes.

Harris, D. E.↗

NASA NTRS1993

The Einstein Observatory catalog of IPC x ray sources. Volume 5E: Right ascension range 12h 00m to 15h 59m

The Einstein Observatory (HEAO-2, launched November 13, 1978) achieved radically improved sensitivity over previous x-ray missions through the use of focusing optics, which simultaneously afforded greatly reduced background and produced true images. During its 2.5-yr mission, the Einstein X-Ray Telescope was pointed toward some 5,000 celestial targets, most of which were detected, and discovered several thousand additional 'serendipitous' sources in the observed fields. This catalog contains contour diagrams and source data, obtained with the imaging proportional counter in the 0.16 to 3.5 keV energy band, and describes methods for recovering upper limits for any sky position within the observed images. The main catalog consists of six volumes (numbered 2 through 7) of right ascension ordered pages, each containing data for one observation. Along with the primary documentation describing how the catalog was constructed, volume 1 contains a complete source list, results for merged fields, a reference system to published papers, and data useful for calculating upper limits and fluxes.

Harris, D. E.↗