ALBERT

Beschreibung: The contributions that the Advanced X-ray Astrophysics Facility (AXAF) is expected to make in key areas of astronomical investigation are examined. Emphasis is given to the planned AXAF investigations of galaxy clusters, dark matter, and the distance scale of the universe. Properties of stars and quasars that AXAF will address are considered, and the most important AXAF characteristics are listed.

Beschreibung: Ideas presented at the Workshop on Astrophysics from the moon, held in Annapolis, Maryland, in February 1990, are discussed. Consideration is given to the formation of stars and planetary systems, the possibility of earthlike planets among the nearby stars, the possible existence of life and intelligence elsewhere, the current status of the sun and other stars, the evolution of the early universe, and environmental and site considerations for initial observatories.

Beschreibung: The Space Infrared Telescope Facility (SIRTF) is a one-meter class observatory for infrared astronomy that will be launched into high earth orbit by NASA in the late 1990's. SIRTF's three focal plane instruments will permit imaging and spectroscopy over most of the infrared spectrum with sensitivities of 100 to 10,000 times their predecessors. This paper briefly reviews SIRTF's capabilities, science objectives, and current status.

Beschreibung: The International Ultraviolet Explorer (IUE) was launched into a geosynchronous orbit on 26 January 1978. It is equipped with a 45-cm mirror and spectrographs operating in the far-ultraviolet (1150-2000 A) and the midultraviolet (1900-3200 A) wavelength regions. In a low-dispersion mode, the spectral resolution is some 6-7 A. In a high-dispersion echelle mode, the resolution is about 0.1 Aat the shortest wavelength and about 0.3 A at the longest. It is a collaborative program among NASA, ESA, and the British SERC. The IUE is operated in real time 16 hours a day from NASA Goddard Space Flight Center near Washington, D.C. and 8 hours daily from ESA's Villafranca groundstation near Madrid, Spain. By the end of 1989, 1870 papers, using IUE observations, have been published in referred journals. During the same period, over 1700 different astronomers from all over the world used the IUE for their research.

Beschreibung: The Hubble Space Telescope was launched from the Kennedy Space Center on April 24, 1990. Its initial check-out indicates that all sub-systems of the satellite are working very well, with two key exceptions: The line-of-sight pointing is subject to occasional jitter apparently induced by thermal stresses in the solar arrays; this is expected to be overcome. The telescope mirrors are found to contain approximately 0.5 wave rms of spherical aberration which cannot be overcome by any controls on board the satellite. This defect will limit the scientific performance of the telescope in the short run. However, the aberration can be fully corrected in the optical designs of future replacement instruments, and the delivery schedules of these instruments are being accelerated.

Beschreibung: A conceptual plan for the development of a comprehensive long duration solar space observatory, The Advanced Solar Observatory (ASO) is described. The ASO is intended to provide solar astronomers with the observational power necessary to address fundamental problems relating to the solar convection zone and activity cycle; the thermal and nonthermal processes that control the transport of energy, mass, and magnetic flux in the solar atmosphere; the generation of the solar wind; and the dynamics of the inner heliosphere. The ASO concept encompasses three proposed Space Station-based instrument ensembles: (1) the High Resolution Telescope Cluster, which includes far ultraviolet, extreme ultraviolet, and X-ray telescopes; (2) the Pinhole/Occulter Facility, which includes Fourier transform and coded aperture hard X-ray and gamma ray telescopes and occulted ultraviolet and visible light coronagraphs; and (3) the High Energy Facility, which contains neutron, gamma ray, and low frequency radio spectrometers. Two other facilities, the Orbiting Solar Laboratory, and a package of Global Dynamics Instrumentation, will, with the Space Station ensembles, form a comprehensive capability for solar physics. The scientific program of the ASO, current instrument concepts for the Space Station based ASO instrument ensembles, and plans for their accommodation on the Space Station are described.

Beschreibung: The outer planet positions of JPL's recent planetary ephemeris, DE 202, have begun to show significant differences from DE 200, the basic ephemeris of the major national almanacs. The differences DE 202 - DE 200 are plotted and are assumed to approximate the errors of DE 200. For Jupiter, the difference in right ascension varies over the planet's 12 yr period between -0.1 and -0.2 arcsec throughout the century; for Saturn, the right ascension also varies over the 30 yr period, but in addition, shows a drift which reaches -0.25 arcsec at present; for Uranus, the difference is small through the first half of the century, but now has reached -0.4 arcsec; for Neptune, the error was +0.6 arcsec at 1900 and is near -1.0 arcsec by the year 2000; the error for Pluto exceeds +2.0 arcsec by the end of the century and is rapidly increasing. The declination errors are generally periodic and smaller than the right ascensions.

Beschreibung: This paper reports the detection of the 3.3-micron emission feature in the center of two external galaxies: IC 694 (interacting with NGC 3690) and NGC 4194 (a merger). This feature has been previously detected in various galactic and extragalactic objects and is thought to be due to very small grains or large molecules that probably belong to the Polycyclic Aromatic Hydrocarbon (PAH) family. Its presence, as well as the IRAS colors, strongly suggest that these galaxies are dominated by starbursts rather than active nuclei. From publishing data and the present observations, the brightness of the feature in different galaxies is studied. A simple model of radiative transfer shows that the 3.3-micron feature brightness of a given galaxy allows the determination of the unreddened surface brightness of the galaxy stellar content. In galaxies with relatively large extinction, the 3.3-micron feature (and the other PAH related features) is therefore a useful spatial indicator of star-formation activity in their centers.

Beschreibung: A complete sample, taken from the Parkes 2.7 GHz catalog, of flat-spectrum radio sources with flux densities greater than 0.5 Jy is described. The sample covers all right ascensions and declinations for +10 deg to -45 deg, excluding the Galactic plane, and contains 403 sources. Attention is drawn to the advantages of radio surveys over optical surveys. The survey is used to highlight some selection effects found in optical surveys. How this sample can be used to give information on the early universe is discussed.

Beschreibung: The Ultra High Resolution XUV Spectroheliograph (UHRXS), a solar observatory planned for the Space Station Freedom, is described. The UHRXR instruments include nine XUV Ritchey-Chretien telescopes covering a spectral range of 70-350 A, which will provide images of solar atmosphere structures ranging in temperature from 50,000 to 20,000,000 K. The images will be obtained with spatial resolution that is an order of magnitude better than any other currently planned solar satellite experiment.

Beschreibung: The possibility of using terrestrial ionospheric focusing to improve the directivity of electric dipoles on space missions has been investigated by comparing simultaneous observations of a solar radio storm by the ISIS 1 and ISIS 2 spacecraft, in near earth orbit, and the ISEE 3 spacecraft located beyond the magnetosphere. To this end, a three-dimensional ray tracing in a spherically stratified ionosphere has been carried out for conditions appropriate to the observations by the ISIS spacecraft of a solar radio storm in September 1983. The procedure allows Poynting flux spectral densities measured on ISIS to be converted to spectral densities well outside the ionosphere where they can be compared directly with simultaneous observations on ISEE 3. The results demonstrate good agreement over their common observing frequency range (1-2 MHz).

Beschreibung: This paper discusses the Astro, a UV and X-ray observatory designed for the Space Shuttle Columbia, which is scheduled for the May 7, 1990 launch. Astro's four telescopes and their operation are described. They are the Hopkins Ultraviolet Telescope, the Wisconsin Ultraviolet Photo-Polarimeter Experiment, the Ultraviolet Imaging Telescope, and the Broad Band X-ray Telescope. Attention is also given to the mission plan and to the ground operations.

Beschreibung: A list of bright (less than 17 mag) southern QSOs and bright (less than 11 mag) stars that may be suitable for the Hubble Space Telescope link between the Hipparcos astrometric reference frame and the VLBI extragalactic frame is presented. The QSOs have been selected from various lists of radio objects and identifications. The stars have been selected from the Strasbourg (CDS) data base and from the Preliminary Second Cape Photographic Catalog, and supplemented with stars measured from the SERC IIIa-J Schmidt survey. These QSOs and stars have been included in the Hipparcos and HST schedule of observations.

Beschreibung: An inspection of 34 SRC/ESO J southern sky fields is the basis of the present list of clusters of galaxies and their approximate classifications in terms of cluster concentration, defined independently of richness and shape-symmetry. Where possible, an estimate of the cluster morphological population is provided. The Bautz-Morgan classification was applied using a strict comparison with clusters on the Palomar Sky Survey. Magnitudes were estimated on the basis of galaxies with photoelectric or photographic magnitudes.

Beschreibung: Preliminary studies have been conducted for the concept of a lunar base supporting astronomical instruments of power comparable to the VLA, giving attention to aperture-synthesis arrays which could improve angular resolution to the level of a few microarcsec. The only conceivable mode of catastrophic instrument failure envisioned would be a meteorite strike, although the probability for this is small and comparable to that encountered in orbital instruments. Nevertheless, lunar dust may pose problems, lunar soil may be inadequate for support of instrument structures, moonquakes may disturb instruments, gravitational deflection may distort them, and heat radiation and scattered light may exert troublesome influences on observations. Representative parameters for a specific system are presented.

Beschreibung: This catalog lists all publications containing new observations of CO isotopes in galaxies that have appeared since the submission of Verter (1985) and before the end of 1989. For each publication the number and nature of the observations are summarized. Condensations of this information can be used to evaluate the current status and direction of observational research on molecular gas in external galaxies.

Beschreibung: Astrometric measurements made with the Mark III stellar interferometer on five nights in August-September 1988 yielded average formal 1-sigma errors for 12 FK5 stars of 6 mas in declination and 10 mas in right ascension. This improvement in precision over previously reported measurements with this instrument made in 1986 is attributable to several factors: a second 12 m baseline; oriented E-S, was added to the instrument to improve the determination of right ascension; two-color analysis was included in the data-reduction process, along with a new central-fringe identification algorithm using three spectral channels, in order to reduce atmospheric errors; thermal control was greatly improved; and changes were made to observational procedures and hardware to monitor variations in the delay offset due to residual thermal drifts. Approximately half of the new positions are within 50 mas of their FK5 positions. However, an extended series of measurements are needed to ascertain the accuracy that can be achieved by interferometry.

Beschreibung: A photographic atlas of polar-ring galaxies and related objects is presented. The atlas includes kinematically confirmed polar-ring galaxies (category A), good candidates based on their morphological appearance (category B), possible candidates (category C), and possibly related objects (category D). New photometric and kinematic observations are reported for several galaxies in the catalog, including observations that show that UGC 7576 and UGC 9796 ( = II ZW 73) are S0 galaxies with polar rings. Roughly 0.5 percent of all nearby S0 galaxies appear to have polar rings. When corrected for various selection effects (e.g., nonoptimal viewing orientation, possible dimming, or limited lifetime of the ring) the percentage increases to about 5 percent of S0 galaxies which have, or have had a polar ring.

Beschreibung: A model describing the physical libration in longitude and latitude for Phobos is derived. The major effect is the well-known longitude variation with the anomalistic orbital period and amplitude. Several additional meter-sized periodic librations in longitude exist. The latitude variation is dominated by the forced precession of Phobos' figure axis with the precession of Phobos' orbital plane. The contribution of Phobos' topography to its gravity field is estimated using the control network model of Duxbury and Callahan (1989).

Beschreibung: An algorithm to calculate source structure corrections for bandwidth synthesis delays and delay rates is used to refer the position of extragalacitc radio sources to a specific feature of each source's morphology. The delay and delay rate are obtained from VBLI observations. The algorithm and its theoretical basis are described, and simulations for a simple two-component source are discussed. VLBI data for the complex radio source NRAO 140 are analyzed. For this source, structure corrections are calculated with maps from three different VLBI imaging techniques: the hybrid-CLEAN algorithm, the maximum entropy method, and model fitting. The calculated structure corrections are compared with brightness distributions to the actual data. The results are used to map NRAO 140. It is found that the CLEAN map produces the most accurate structure corrections.

Beschreibung: Observations from 600 Mark III VLBI experiments from 1979 to 1988, resulting in 237,681 acceptable pairs of group delay and phase delay rate observations, have been used to derive positions of 182 extragalactic radio sources with typical formal standard errors less than 1 mas. The sources are distributed fairly evenly above delta = -30 deg, and 70 sources have delta greater than 0 deg. Analysis with different troposphere models, as well as internal and external comparisons, indicates that a coordinate frame defined by this set of radio sources should be reliable at the 1 mas level. The right ascension zero point of this reference frame has been aligned with the FK5 by using the optical positions of 28 extragalactic radio sources whose positions are on the FK5 system. Because of known defects in the knowledge of astronomical constants, daily nutation offsets in longitude and obliquity were determined relative to an arbitrary reference day in the set of experiments.

Beschreibung: Redshifts were measured for a complete sample of galaxies detected by the IRAS within 11.5 deg of the center of the void in Bootes discovered by Kirshner et al (1981). There are 12 IRAS galaxies within the void as defined by the above authors, seven of which were discovered in this survey. One of these has a companion at the same redshift. The resulting density of IRAS galaxies in the void is measured to be between 1/6 and 1/3 of the average density; the uncertainty is dominated by Poisson statistics. Good agreement is found between the selection function and number density derived from the present sample and those derived from the all-sky sample of Strauss (1989). The optical spectra of the newly found galaxies in the void are typical of IRAS galaxies in the field.

Beschreibung: Continuing improvements in the lasers and the detection electronics over the years which have led to accurate measurements of the distance from the earth to the moon are discussed. The first reflector of laser light pulses, deployed on the moon surface twenty years ago by the Apollo 11 astronauts, consisted of 100 fused silica corner cubes, and reflected a beam of light directly back toward its point of origin. Observatories located in Texas, Hawaii, and France now regularly range the moon with an accuracy of approximately 1 inch. Ranging programs have also been carried out in Australia and the Soviet Union. The ranges are computer-analyzed to determine precisely the positions of the observatories on earth, the positions of the reflectors on the moon, the orbit of the moon around the earth, and the rotation and orientation of the earth and the moon. The most important scientific advances derived from lunar ranging are also reviewed.

Beschreibung: This paper discusses the application of active structures technology to the control of precision structures for future space-based astrophysics observatories. The state of the art in active structures is reviewed and technology developments applicable to large optical systems are discussed.

Beschreibung: This paper documents the planetary observational data used in a series of ephemerides produced at JPL over six years preceding the creation of DE118/LE62, the set which transformed directly into the JD2000-based set, DE200/LE200. Details of the data reduction procedures are presented, and techniques to overcome the uncertainties due to planetary topography are described. For the spacecraft data, the basic reductions are augmented by formulations for locating the transponder, whether in orbit or landed on the surface of a planet.

Beschreibung: New Technology Telescope (NTT) images of 16 southern ultraluminous infrared (LIR greater than 10 to the 12th solar luminosities) galaxies in the Local Universe (z less than 0.13) are presented. All these galaxies are strongly interacting systems showing double nuclei, wisps, and tails that are characteristic of advanced mergers. The most spectacular instance of these cosmic accidents is the 'superantenna', a system with long slender tails that extend over 500 kpc. It is concluded that ultraluminous infrared galaxies are mergers of giant spiral galaxies, and that the distinguishing features of tidal interactions in this type of galaxies become blurred at higher redshifts. The CCD images suggest the existence of a critical separation between the colliding galaxies of about 10 kpc at which the merging systems become ultraluminous in the infrared.

Beschreibung: The ability of a space-based radio interferometer array to make high resolution images at frequencies of only a few MHz will be limited by interplanetary scintillation. Numerical simulations have been used to study the severity of interferometer phase fluctuations caused by the density fluctuations in the solar wind over a range of frequencies and solar elongation angles. The impact of these fluctuations on the quality of radio images produced has also been investigated. The results show that, for baselines up to 100 km, accurate imaging should be possible when nu sin (epsilon/2) is equal to or greater than 2.5, where nu is the observing frequency in MHz and epsilon is the solar elongation angle.

Beschreibung: A mid-IR Michelson interferometer capable of obtaining 0.002/cm resolution solar spectra has been developed for balloon use. The interferometer is based on the Bomem self-aligning instrument, and is equipped with a solar tracking system, telemetry, and recording systems, as well as temperature control and gondola orientation. The interferometer has made two successful flights in the 7-14-micron interval up to 40 km. The basic systems are described and sample spectra are presented.

Beschreibung: X-ray fluxes or upper limits in the 2-10 keV energy band from the HEAO 1 A-2 experiment are given for well-defined samples of QSOs and of Seyfert galaxies of types 1, 1.5 and 2, and for a list of BL Lac objects (334 sources in total). All on-orbit X-ray measurements of these objects published between 1976 and 1986 from other experiments have also been cataloged.

Beschreibung: The prediction of the magnitude of the faintest star visible through a telescope by a visual observer is a difficult problem in physiology. Many prediction formulas have been advanced over the years, but most do not even consider the magnification used. Here, the prediction algorithm problem is attacked with two complimentary approaches: (1) First, a theoretical algorithm was developed based on physiological data for the sensitivity of the eye. This algorithm also accounts for the transmission of the atmosphere and the telescope, the brightness of the sky, the color of the star, the age of the observer, the aperture, and the magnification. (2) Second, 314 observed values for the limiting magnitude were collected as a test of the formula. It is found that the formula does accurately predict the average observed limiting magnitudes under all conditions.

Beschreibung: A new generation of photoelectric astrometric telescopes promises significant advances for both semiglobal and differential astrometry. Some of these new telescopes have a Ronchi ruling at the prime focal plane. The images move relative to the ruling, behind which photomultipliers or similar detectors view the modulated transmitted light. When several stars are viewed simultaneously, this technique exploits correlations in the atmospheric seeing to significantly improve differential astrometric precision. This article presents some general design and analysis criteria for this type of telescope and describes the particular reflector telescope. This has a 29-cm aperture and has met a 4-milli-arc-second differential precision per 5-minute observation. The system is designed for a program of improved annual parallax and solar-system object measurements.

Beschreibung: Eichhorn and Googe (1969) present formulas for incorporating a new position measurement into an existing star catalog. Their result is extended to the case where the new measurement also includes proper motion, thereby enabling one to combine the positions and proper motions from two catalogs.

Beschreibung: The Space Infrared Telescope Facility (SIRTF) is planned for launch by NASA in the mid-1990's. It will be a cryogenically-cooled observatory for infrared astronomy and will carry several focal plane instruments which will provide a wide range of imaging, photometric, and spectroscopic capabilities. SIRTF will build on the scientific and technical progress of the successful IRAS mission and take the next step in the exploration of the Universe at infrared wavelengths. Most of the observing time during the five-to-ten year SIRTF mission will be available to General Investigators, so there will be ample opportunities for the pursuit of problems originating from within the Space Life Sciences community. Here, a review is given of the capabilities of SIRTF for this style of investigation, using the study of carbon in the Galaxy as a specific example. The very high sensitivity of SIRTF's spectrometers to diffuse emission will allow studies of carbon in both the gaseous and solid phase in the interstellar medium and should be of particular importance for the identification of the carbon-bearing macromolecules believed to be responsible for the emission features identified in the near infrared. SIRTF will also carry out studies of a wide variety of evolved stars which are returning gas and solid phase carbon to the interstellar medium and contribute to our understanding of the carbon budget in the Galaxy. These studies in the area of galactic astronomy will be complemented by detailed investigations of carbon-bearing compounds in solar system objects, including the surfaces of distant asteroids and cometary nuclei which are too faint to be studied in any other way.

Beschreibung: In the outer envelopes of red giants, when the gas cools sufficiently, molecules and solids form. Thermodynamically, the most stable molecule is CO, and it is usually assumed that all the available carbon and oxygen are consumed in the formation of this molecule (Salpeter 1977). If the carbon abundance is greater than the oxygen abundance, then the carbon left over after the formation of CO is available for solid grains. Because carbon is by far the most abundant species available for making solids in these environments, researchers anticipate that the grains are composed of nearly pure carbon in some form. The observations which can be used to infer the nature of this solid phase carbon are discussed. The observations of the dust around carbon-rich red giants are discussed. These results are then placed into their broader astrophysical context.

Beschreibung: Using the results of gamma-ray, millimeter wave and far surveys of the galaxy, logically consistent picture of the large scale distribution of galactic gas and cosmic rays was derived, tied to the overall processes of stellar birth and destruction on a galactic scale. Using the results of the IRAS far-infrared survey of te galaxy, the large scale radial distributions of galactic far-infrared emission independently was obtained for both the Northern and Southern Hemisphere sides of the Galaxy. The dominant feature in these distributions was found to be a broad peak coincident with the 5 kpc molecular gas cloud ring. Evidence was found for spiral arm features. Strong correlations are evident between the large scale galactic distributions of far-infrared emission, gamma-ray emission and total CO emission. There is particularly tight correlation between the distribution of warm molecular clouds and far-infrared emission on a galactic scale. The 5 kpc ring was evident in existing galactic gamma-ray data. The extent to which the more detailed spiral arm features are evident in the more resolved EGRET (Energetic Gamma-Ray Experimental Telescope) data will help to determine more precisely the propagation characteristics of cosmic rays.

Beschreibung: The Precision Segmented Reflector (PSR) project which is developing telescope technology needed for future spaceborne submillimeter astronomy missions is described. Four major technical areas are under development. Lighweight composite mirrors and associated materials, precision structures and segmented reflector figure sensing and control are discussed. The objectives of the PSR project, approaches, and project technology status, are reported.

Beschreibung: Components for the key elements of submillimeter wave heterodyne receivers are described. The devices and components are inherently space qualifiable having low power and mass needs and exhibiting robustness. Nb and NbN superconductor insulator superconductor (SIS) tunnel junctions are selected for the nonlinear mixing element because of their robustness. NbN exhibits a large superconducting bandgap, allowing operation in excess of 1500 GHz. Both waveguide mounts, for the lower frequencies and planar antenna mixer mounts for the higher frequency range, are used. Quasi-optical components are used for frequency multiplexing and combining.

Beschreibung: Surveys made at wavelengths shorter than 100 microns are criticized in that they are biased against finding the coldest, most deeply obscured, and possibly youngest protostars. Large scale mapping of star forming regions in the submillimeter continuum and in lines such as CS H2CO and NH3, that are excited at high density, is identified as crucial in order to find clouds in the earliest stages of collapse into stars. The use of photometry from 1 to 1000 microns in characterizing the disks around embedded stars and T Tauri stars is outlined.

Beschreibung: SOFIA, an airborne observatory intended to be carried aboard a Boeing 747 high performance aircraft, is described. The observatory is predicted to provide a threefold greater aperture than that of the Kuiper telescope. The Boeing aircraft will carry the 2.5 diameter telescope and its observers to altitudes of 14,000 and above where the atmosphere is very nearly transparent at all wavelengths. Various aspects and specific missions of the SOFIA project, a cooperative venture of the U.S. and Germany, are described.

Beschreibung: The two major sources of confusion that limit the sensitivity of continuum observations at submillimeter wavelengths outside the galactic plane are discussed. One of the sources is the spatial structure of the thermal emission from dust in the Milky Way. The crowding of extragalactic sources at faint levels is the second source of confusion. Estimates of the noise expected from these two types of confusion as a function of wavelength and beam size on the sky are presented and compared to detector and photon noise estimates for proposed spaceborne telescopes.

Beschreibung: The Cosmic Background Explorer, launched 18 Nov. 1989, has nearly completed its first full mapping of the sky with all three of its instruments: A Far Infrared Absolute Spectrometer (FIRAS) covering 0.1 to 10 mm, a set of Differential Microwave Radiometers (DMR) operating at 3.3, 5.7, and 9.6 mm, and a diffuse Infrared Background Experiment (DIRBE) spanning 1 to 300 microns in ten bands. A preliminary map of the sky derived from DIRBE data is presented. Initial cosmological implications include: a limit on the comptonization parameter of 0.001, on the chemical potential parameter of 0.01, a strong limit on the existence of a hot smooth intergalactic medium, and a confirmation that the dipole anisotropy has the spectrum expected from a Doppler shift of a blackbody. There are no significant anisotropies in the microwave sky detected, other than from our own galaxy and a cos theta dipole anisotropy whose amplitude and direction agree with previous data. At shorter wavelengths, the sky spectrum and anisotropies are dominated by emission from local sources of emission within our Galaxy and Solar System. Preliminary comparison of IRAS (Infrared Astronomical Satellite) and DRIBE sky brightnesses toward the ecliptic poles shows the IRAS values to be significantly higher than found by DRIBE at 100 microns. The presence of gain and zero point errors in the IRAS total brightness data is suggested. The spacecraft, instrument designs, and data reduction methods are described.

Beschreibung: An overview of the subdivision of wavelength ranges, importance of extinction, observing techniques, and scientific objectives in both IR broadband measurement and spectroscopy is given. Infrared and millimeter wave spectroscopy in the galaxy and IR and millimeter wave observations for Centaurus A are examined and discussed.

Beschreibung: The Gamma-Ray Observatory (GRO) which is part of NASA's Great Observatories space program is presented. The GRO is equipped with the Burst and Transient Source Experiment (which detects low-energy gamma-ray photons from 20 keV to 600 keV and locates sources of gamma-ray bursts), the Oriented Scintillation Spectrometer Experiment (which detects celestial gamma rays from 100 keV to 10 MeV and identifies the elements producing these rays by measuring the ray's spectra and time variability), the Imaging Compton Telescope (which images gamma rays with energies from 1 to 30 MeV created when cosmic rays interact with interstellar matter), and the Energetic Gamma-Ray Experiment Telescope (which detects high-energy photons associated with the most energetic processes occurring in nature). After the energies of photons from each source are classified, the gamma-ray mechanisms can be modelled. Nuclei, radioactive isotopes, and nuclear reactions can be identified, and the physical conditions at the radiation's source can also be modelled. From these models, theories can be developed about the creation of elements in the explosion and collapse of giant stars, the acceleration of charged particles to velocities approaching the speed of light, and the destruction of matter and antimatter.

Beschreibung: Five methods for obtaining linear regression fits to bivariate data with unknown or insignificant measurement errors are discussed: ordinary least-squares (OLS) regression of Y on X, OLS regression of X on Y, the bisector of the two OLS lines, orthogonal regression, and 'reduced major-axis' regression. These methods have been used by various researchers in observational astronomy, most importantly in cosmic distance scale applications. Formulas for calculating the slope and intercept coefficients and their uncertainties are given for all the methods, including a new general form of the OLS variance estimates. The accuracy of the formulas was confirmed using numerical simulations. The applicability of the procedures is discussed with respect to their mathematical properties, the nature of the astronomical data under consideration, and the scientific purpose of the regression. It is found that, for problems needing symmetrical treatment of the variables, the OLS bisector performs significantly better than orthogonal or reduced major-axis regression.

Beschreibung: This article presents the results of a fit of numerically integrated Neptunian satellite orbits to earth-based astrometric observations and early Voyager spacecraft observations. Ephemerides based on these orbits were used by the Voyager project as the final pre-encounter ephemerides. As a by-product of the orbit fits, estimates of the Neptune mass, the second zonal harmonic of Neptune, and the pole orientation of Neptune were also obtained.

Beschreibung: Variations in astronomical refraction near the horizon are examined. Sunset timings, a sextant mounted on a tripod, and a temperature profile are utilized to derive the variations in refraction data, collected from 7 locations. It is determined that the refraction ranges from 0.234 to 1.678 deg with an rms deviation of 0.16, and it is observed that the variation is larger than previously supposed. Some applications for the variation of refraction value are discussed.

Beschreibung: High-resolution X-ray and EUV images of the solar corona have been obtained with two rocket-borne normal incidence Cassegrain multilayer telescopes. The Cassegrain images correspond to material at about 10 to the 6th K and about 80,000 K. Other images, at somewhat lower resolution, were obtained with Herschelian multilayer telescopes and Wolter-Schwarzschild hybrid grazing incidence/multilayer optical systems. The Cassegrain and Herschelian images are discussed emphasizing the analysis of polar plumes observed at the limb of the sun. The application of specific multilayer techniques to astronomical observations is discussed, emphasizing observations of the sun. Current efforts to develop a comprehensive Multi-Spectral Solar Telescope Array rocket instrument for the study of a wide variety of problems related to the solar atmosphere are reported.

Beschreibung: The VLA has been used in its A-, B-, C-, and D-configurations to make 1.49 GHz maps of sources in both the original and revised IRAS Bright Galaxy Samples of strong extragalactic sources selected at a wavelength of 60 microns. Integrated 1.49 GHz flux densities were obtained from the lowest resolution maps, and maps were made with higher resolution so that nearly all of the radio sources have been at least partially resolved. Only NGC 1377 was not detected at 1.49 GHz. An atlas of contour maps, a table of total flux densities plus other radio source parameters, and references to published radio maps are given. Since the infrared and radio continuum brightness distributions of IR-selected galaxies are usually similar, these high-resolution radio maps can be used as substitutes for the unavailable IR maps to indicate the sizes and precise locations of the IR-emitting regions.

Beschreibung: The white dwarf G29 - 38 was shown by Zuckerman and Becklin (1987) to have an IR excess at 1-5 microns, possibly due to a spatially unresolved brown dwarf companion. Using the NASA-MSFC 20-pixel bolometer array at the IRTF, a 10.8-micron flux density of 9.5 + or - 3.1 mJy is detected from G29 - 38. This value, combined with more recent 10-micron data obtained by others, implies that 10-micron emission from G29 - 38 is at least twice that expected from a brown dwarf having an effective temperature in the range 1100-1500 K, as previously estimated. The possibility that the IR excess is emitted by dust rather than a brown dwarf is therefore strengthened.

Beschreibung: A 4.9 m diameter antenna in earth orbit, part of the Tracking and Data Relay Satellite System, was previously used for space VLBI observations at 2.3 GHz. It has now been used successfully with two ground antennas for VLBI measurements at 15 GHz. Although the sensitivity (gain/system temperature) of the orbiting antenna was a factor of 6 poorer at 15 GHz than at 2.3 GHz, 11 out of 22 extragalactic sources were detected on space-ground baselines, up to a maximum baseline of 1.63 earth diameters. The results suggest that the distribution of source visibilities at 15 and 2.3 GHz are similar for these baseline lengths. Model-dependent brightness temperatures of 1-2.5 x 10 to the 12th K were derived for six sources. This suggests that sources with brightness temperatures in this range are as common at 15 GHz as at 2.3 GHz. The coherence on space-ground baselines (this includes effects due to the phase transfer from the ground to the satellite and the reconstruction of the spacecraft orbit) was 0.76 for 340 s integrations.

Beschreibung: Entries in the Guide Star Catalog (GSC) within three southern declination fields surveyed by Ratnatunga in 1983 are studied. All three fields have high galactic latitude. About 98 percent of the 13,540 GSC entries within the total survey area of 60 deg sq are cross identified. Using over 9000 stars in the magnitude range J between 12.5 and 15.5, the random rms precision in photometric magnitude within these fields is estimated to be 0.1-0.2 mag, much lower than the total rms accuracy of 0.4 mag estimated in GSC. Some of the scanned images of the remaining unmatched entries were visually inspected to identify the cause of discrepancy.

Beschreibung: A catalogue is presented of all the low-resolution IUE spectra of dwarf novae and nova-like stars that were recorded until the end of 1987. All spectra have been reduced, and are displayed, in a homogeneous way. In addition to details about these data, to the extent available, their position in the outburst light curves is given, physical information about each system, and a comprehensive list of references for published observations in all wavelength ranges.

Beschreibung: The capabilities of the X-ray Timing Explorer (XTE) are described with particular attention paid to current scientific problems it will address, from galactic neutron star systems to active galactic nuclei. It features a low-background continuous 2-200 keV response with large apertures (a 0.63 sq m proportional counter array and a 0.16 sq m dual rocking NaI/CsI scintillation array). Rapid response (in hours) to temporal phenomena, e.g., transients, is obtained by virtue of a scanning all-sky monitor and rapid maneuverability. The XTE will carry out detailed energy-resolved studies of phenomena close to neutron stars (e.g., quasi-periodic oscillations) because of its submillisecond timing (to 10 microsec), its high telemetry rates (to 256 kbs), and the high throughput of its data system (to greater than about (200,000 c/sec).

Beschreibung: The present volume on observations in earth orbit and beyond discusses current and future missions, launch vehicles, the relative merits of various observatories, and long-term future issues. Attention is given to the Granat automatic spacecraft, the prospects of the Hipparcos mission, EUV and FUV astronomy from Voyagers 1 and 2, and the X-ray Timing Explorer. Topics addressed include the SAX mission for X-ray astronomy, the Space Infrared Telescope Facility, the Ulysses mission in the high-latitude heliosphere, and science operations for future space astrophysics missions. Also discussed are science observations with the IUE using the one-gyro mode, new methods of determining spacecraft attitude, cryogenic testing of optics for ISOCAM, and the stellar X-ray polarimeter for the Spectrum-X-Gamma mission.

Beschreibung: The machine-readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The Basic FK5 provides improved mean positions and proper motions for the 1535 classical fundamental stars that had been included in the FK3 and FK4 catalogs. The machine version of the catalog contains the positions and proper motions of the Basic FK5 stars for the epochs and equinoxes J2000.0 and B1950.0, the mean epochs of individual observed right ascensions and declinations used to determine the final positions, and the mean errors of the final positions and proper motions for the reported epochs. The cross identifications to other designations used for the FK5 stars that are given in the published catalog were not included in the original machine versions, but the Durchmusterung numbers have been added at the Astronomical Data Center.

Beschreibung: The machine readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The catalog contains accurate equatorial coordinates for 4551 stars in a band of sky against which cameras of the Voyager spacecraft were pointed for observations in the region of Saturn during the flyby. All of the reference stars are in the range 12(exp h) 40(exp m) to 14(exp h) 12(exp m) in right ascension (1950) and +02 to -09 degs in declination. Mean errors of the positions are about 0.25 sec.

Beschreibung: The different materials that could be used to design the pedestal for a Moon based 16 meter telescope are discussed. The material that should be used has a low coefficient of thermal expansion, high modulus of elasticity, and high compressive and tensile strengths. For the model developed in this study, an aluminum-manganese alloy was used because of its low coefficient of thermal expansion. Due to variations in lunar soil conditions, both vertically and horizontally, three foundation systems are presented. The spudcan footing can be used in the case where dense soil is more than three meters. The spread footing is recommended where the dense soil is between one and three meters. Finally, in the third system, the Lunar Excursion Vehicle (LEV) is used as a base support for the telescope's pedestal. The LEV support requires a prepared site. The soil should be compacted and stabilized, if necessary, to reduce settlement.

Beschreibung: The digital frequency synthesizer (DFS) is an integral part of the programmable local oscillator (PLO) which is being developed for the NASA's Deep Space Network (DSN) and radar astronomy. Here, the theory of operation and the design of the DFS are discussed, and the design parameters in application for the Goldstone Solar System Radar (GSSR) are specified. The spectral purity of the DFS is evaluated by analytically evaluating the output spectrum of the DFS. A novel architecture is proposed for the design of the DFS with a frequency resolution of 1/2(exp 48) of the clock frequency (0.35 mu Hz at 100 MHz), a phase resolution of 0.0056 degrees (16 bits), and a frequency spur attenuation of -96 dBc.

Beschreibung: Results of a wind tunnel test of a new concept in observatory dome design, the Fixed Shutter Dome are presented. From an aerodynamic standpoint, the new dome configuration is similar in overall shape to conventional observatory domes, with the exception of the telescope viewing aperture. The new design consists of a circular aperture of reduced area in contrast to conventional domes with rectangular or slotted openings. Wind tunnel results of a side-by-side comparison of the new dome with a conventional dome demonstrate that the mean and fluctuating velocity through the aperture and in the center of the new dome configuration are lower than those of conventional domes, thus reducing the likelihood of telescope flow-induced vibration.

Beschreibung: Using high resolution and high sensitivity IRAS data at 12 and 25 microns low mass stars were studied which have recently formed in the Ophiuchus, Corona Australis, and IC1396 dark clouds. The successful application of these techniques to the Rho Ophiuchi infrared cluster is briefly described. The status of research performed is also presented.

Beschreibung: A multispectral glancing incidence x ray telescope is disclosed, which capable of broadband, high resolution imaging of solar and stellar x ray and extreme ultraviolet radiation sources includes a primary optical system which focuses the incoming radiation to a primary focus. Two or more ellipsoidal mirrors are positioned behind the primary focus at an inclination to the optical axis, each mirror having a concave surface coated with a multilayer synthetic microstructure coating to reflect a desired wavelength. The ellipsoidal mirrors are segments of respective ellipsoids having a common first focus coincident with the primary focus. A detector such as an x ray sensitive photographic film is positioned at the second focus of each of the ellipsoids so that each of the ellipsoidal mirrors may reflect the image at the first focus to the detector. In one embodiment the mirrors are inclined at different angles and has its respective second focus at a different location, separate detectors being located at the respective second focus. The mirrors are arranged so that the magnification and field of view differ, and a solenoid activated arm may withdraw at least one mirror from the beam to select the mirror upon which the beam is to impinge so that selected magnifications and fields of view may be detected.

Beschreibung: The Nancay decimetric Radio Telescope (NRT) in Nancay, France, is described, and its potential use for Search for Extraterrestrial Intelligence (SETI) observations is discussed. The conclusion reached is that the NRT is well suited for SETI observations because of its large collecting area, its large sky coverage, and its wideband frequency capability. However, a number of improvements are necessary in order to take full advantage of the system in carrying out an efficient SETI program. In particular, system sensitivity should be increased. This can be achieved through a series of improvements to the system, including lowering the ground pickup noise through the use of ground reflectors and more efficient feed design, and by using low-noise amplifier front ends.

Beschreibung: The machine-readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The catalog contains accurate equatorial coordinates for 4983 stars in a band of sky against which cameras of the Voyager spacecraft were pointed for observations in the region of Jupiter during the flyby. All of the reference stars are in the range 6 hr 00 min to 8 hr 04 min in right ascension (1950), declination zones +16 to +23 degrees, and 8 hr to 31 min to 8 hr 57 min, zones +08 to +14 degrees. Mean errors of the positions are about 0.4 sec.

Beschreibung: Large scale maps of the face of spiral galaxies M51, M83, and NGC 6946 in the 158 micron (C II) fine structure line. The maps are obtained from the Far-infrared Imaging Fabry-Perot Interferometer (FIFI) during its first series of flights on board the Kuiper Airborne Observatory. The (C II) line emission is ubiquitous and easily traced over the mapped regions of each of the galaxies. The (C II) maps are compared with those obtained with similar sized beams in the CO line. The data available from these maps is interpreted.

Beschreibung: The Extreme Ultraviolet Explorer mission is described. The satellite is now scheduled to be launched in September, 1991. For the first six months, an all sky survey will be carried out covering 90 to 820 A, or essentially the entire EUV bandpass. This EUV survey will be made in four bands, or colors, 90-150 A; 170-250 A, 400-600 A, and 550-750 A. A portion of the sky which is free from the normally intense 304 A geocoronal helium background will be surveyed at greater sensitivity. Following the sky survey portion of the mission, spectroscopy of individual sources will be carried out. Three spectrometers employing novel variable line spaced gratings will provide spectra with about 1 A resolution over the band from 90 to 800 A.

Beschreibung: Cool star winds can best be observed in resonance absorption lines seen in the spectrum of a hot companion, due to the wind passing in front of the blue star. We calculated absorption line profiles that would be seen in the ultraviolet part of the blue companion spectrum. Line profiles are derived for different radial dependences of the cool star wind and for different orbital phases of the binary. Bowen and Wilson find theoretically that stellar pulsations drive mass loss. We therefore apply our calculations to the Cepheid binary S Muscae which has a B5V companion. We find an upper limit for the Cepheid mass loss of M less than or equal to 7 x 10(exp -10) solar mass per year provided that the stellar wind of the companion does not influence the Cepheid wind at large distances.

Beschreibung: The ability of the EGRET (Energetic Gamma-Ray Experimental Telescope) to determine the spectral parameters of point sources in 14-day exposures, as planned for the initial survey phase of the GRO (Gamma Ray Observatory) mission, is explored by numerical simulation. Results are given for both galactic and extragalactic objects as a function of source strength and for representative levels of diffuse background emission.

Beschreibung: Nearly simultaneous optical, ultraviolet, and x ray observations of three low redshift quasars are presented. The EXOSAT x ray spectra span the range of observed spectral indices for quasars from the canonical 0.7 energy index typical of Seyfert galaxies for PG0923+129 (Mrk 705) to the steep spectral indices frequently seen in higher luminosity quasars with an index of 1.58 for PG0844+349 (Ton 951). None of the quasars exhibits any evidence for a soft x ray excess. This is consistent with accretion disk spectra fit to the IR through UV continua of the quasars -- the best fitting disk spectra peak at approximately 6 eV with black hole masses in the range 5 x 10(exp 7) to 1 x 10(exp 9) solar mass and mass accretion rates of approximately 0.1 times the Eddington-limited rate. These rather soft disk spectra are also compatible with the observed optical and ultraviolet line ratios.

Beschreibung: Researchers searched for interstellar methane in the spectra of infrared sources embedded in molecular clouds. New observations of several lines of the P and R branches of the nu 3 band of CH4 near 3.3 microns give column densities in the range N less than 1(-2) times 10 to the minus 16th power cm(-2). Resulting abundance ratios are (CH4)/(CO) less than 3.3 times 10 to the minus 2nd power toward GL961 in NGC 2244 and less than 2.4 times 10 to the minus 3rd power toward GL989 in the NGC 2264 molecular cloud. The limits, and those determined in earlier observations of BN in Orion and GL490, suggest that there is little methane in molecular clouds. The result agrees with predictions of chemical models. Exceptions could occur in clouds where oxygen may be depleted, for example by H2O freezing on grains. The present observations probably did not sample such regions.

Beschreibung: Discussed here are new observations of 3-carbon-containing interstellar molecules which play an important role in the chemistry of dense molecular clouds: protonated carbon dioxide, formic acid, and propynal. In 1984 a new oxide of carbon, C3O, was discovered in the interstellar medium (Matthews et al. 1984; Brown et al. 1985). Theoretical models suggest that C3O is produced by dissociative electron recombination with the ion H3C3O+. Although no laboratory data for the branching ratios of such a recombination exist, it seemed to us likely that additional products would include H2C3O. This molecule has more than one isomeric form, but one stable species is propynal (HC2CHO), which had been suggested as a possible interstellar molecule by Winnewisser (1973). In observations at the National Radio Astronomy Observatory 43 m telescope in Green Bank earlier this year, researchers detected a line in the cold cloud TMC-1 which they assign to the 2(0,2)-1(0,1) transition of propynal. The observed line agrees with the laboratory frequency to well within the experimental uncertainty a few parts in 10 to the 7th power. Researchers sought and failed to detect the corresponding 2(1,1)-1(1,0) line, which is understandable given the presence of both a and b components of the electric dipole moment in propynal. The b type transitions will drain population from energy levels with K(sub p) does not equal 0 into the K(sub p) equal 0 stack. If the researchers' assignment is correct, this is the first interstellar detection of propynal. Assuming typical rotational temperatures for TMC-1 and that the line is optically thin, the column density determined is about 5 times 10 to the 12th power cm to the -2nd power, or about three times that for C3O. Formic acid (HCOOH) was the first organic acid to be observed in the interstellar medium, in the Galactic center source Sgr B2. The only other interstellar detection has been recently made in the giant molecular cloud in Orion. As part of the same project that led to the detection of propynal, researchers sought formic acid in the nearby, cold dark clouds TMC-1 and L134N. It is seen only in L134N. This difference between the two clouds appears to be consistent with a model in which the oxygen/carbon ratio is higher in L134N. This would be consistent with the higher abundances for SO and SO2, observed in that cloud, and the higher abundances of many carbon-rich species in TMC-1 (Irvine et al. 1985).

Beschreibung: Preliminary results are presented from COBE's three observational instruments. These are the FIRAS spectrum experiment, which surveyed over 98 percent of the sky, the IR background experiment, DIRBE which surveyed all of the sky, and the DMR anisotropy experiment. It is found that the cosmic microwave background is very close to a blackbody, with a temperature of 2.735 + or - 0.06 K. The only reliably detected background anisotropy is the 3.3 + or - 0.2 mK-amplitude dipole. The rms quadrupole anisotropy is less than 0.00003 with 95-percent confidence. DIRBE results indicate that the IRAS 60-100 micron diffuse-flux calibrations suffer from gain and offset errors.

Beschreibung: The final report on project NAG5-78, 'IUE Observations of B Supergiants in the Large Magellanic Cloud', a collaborative effort between Garmany (U. of Colorado), Sonneborn (Goddard Space Flight Center) and Fitzpatrick (Princeton Univ.) is presented. Over 90 B supergiants in the Large Magellanic Cloud with the IUE satellite, using the low dispersion mode were observed. These stars were chosen because they resemble the precursor star to SN 1987a, and a data base in the continuing effort to understand why the precursor star was a blue, not a red supergiant was needed. The observations were all reduced and made into an atlas, and efforts to understand the evolutionary history of stars of the H-R diagram are underway.

Beschreibung: The Goddard High Resolution Spectrograph (GHRS) is an ultraviolet spectrometer which has been designed to exploit the imaging and pointing capabilities of the Hubble Space Telescope. It will obtain observations of astronomical sources with greater spectral, spatial and temporal resolution than has been possible with previous space-based instruments. Data from the GHRS will be applicable to many types of scientific investigations, including studies of the interstellar medium, stellar winds, chromospheres and coronae, the byproducts and endproducts of stellar evolution, planetary atmospheres, comets, and many kinds of extragalactic sources. This handbook is intended to introduce the GHRS to potential users. The main purpose is to provide enough information to explore the feasibility of possible research projects and to plan, propose and execute a set of observations. An overview of the instrument performance, which should allow one to evaluate the suitability of the GHRS to specific projects, and a somewhat more detailed description of the GHRS hardware are given. How observing programs will be carried out, the various operating modes of the instrument, and the specific information about the performance of the instrument needed to plan an observation are discussed.

Beschreibung: The framework for quantitative scientific analysis with the Hubble Space Telescope (HST) will be established from a detailed calibration program, and a major responsibility of staff in the Telescope & Instruments Branch (TIB) is the development and maintenance of this calibration for the instruments and the telescope. The first in-orbit calibration will be performed by the SI Investigation Definition Teams (IDTs) during the Science Verification (SV) period in Cycle 0 (expected to start 3 months after launch and last for 5 months). Subsequently, instrument scientists in the TIB become responsible for all aspects of the calibration program. Because of the long lead times involved, TIB scientists have already formulated a calibration plan for the next observing period, Cycle 1 (expected to last a year after the end of SV), which has been reviewed and approved by the STScI Director. The purpose here is to describe the contents of this plan. Our primary aim has been to maintain through Cycle 1 the level of calibration that is anticipated by the end of SV. Anticipated accuracies are given here in tabular form - of course, these accuracies can only be best guesses because we do not know how each instrument will actually perform on-orbit. The calibration accuracies are expected to satisfy the normal needs of both the General Observers (GOs) and the Guaranteed Time Observers (GTOs).

Beschreibung: The Faint Object Spectrograph (FOS) has undergone substantial rework since the 1985 FOS Instrument Handbook was published, and we are now more knowledgeable regarding the spacecraft and instrument operations requirements and constraints. The formal system for observation specification has also evolved considerably, as the GTO programs were defined in detail. This supplement to the FOS Instrument Handbook addresses the important aspects of these changes, to facilitate proper selection and specification of FOS observing programs. Since the Handbook was published, the FOS red detector has been replaced twice, first with the best available spare in 1985 (which proved to have a poor, and steadily degrading red response), and later with a newly developed Digicon, which exhibits a high, stable efficiency and a dark-count rate less than half that of its predecessors. Also, the FOS optical train was realigned in 1987-88 to eliminate considerable beam-vignetting losses, and the collimators were both removed and recoated for greater reflectivity. Following the optics and detector rework, the FOS was carefully recalibrated (although only ambient measurements were possible, so the far-UV characteristics could not be re-evaluated directly). The resulting efficiency curves, including improved estimates of the telescope throughput, are shown. A number of changes in the observing-mode specifications and addition of several optional parameters resulted as the Proposal Instructions were honed during the last year. Target-brightness limitations, which have only recently been formulated carefully, are described. Although these restrictions are very conservative, it is imperative that the detector safety be guarded closely, especially during the initial stages of flight operations. Restrictions on the use of the internal calibration lamps and aperture-illumination sources (TA LEDs), also resulting from detector safety considerations, are outlined. Finally, many changes have been made to the instructions for target acquisition specification.

Beschreibung: Selected information from the current Hubble Space Telescope (HST) science programs for the Guaranteed Time Observers (GTO's) and General Observers (GO's) is presented. Included are program abstracts, detailed listings of specific targets, and exposure information.

Beschreibung: This manual is a guide for astronomers who intend to use the High Speed Photometer (HSP), one of the scientific instruments onboard the Hubble Space Telescope (HST). All the information needed for ordinary uses of the HSP is presented, including: (1) an overview of the instrument; (2) a detailed description of some details of the HSP-ST system that may be important for some observations; (3) tables and figures describing the sensitivity and limitations of the HSP; (4) how to go about planning an observation with the HSP; and (5) a description of the standard calibration to be applied to HSP data and the resulting data products.

Beschreibung: An overview is presented of the development and construction of the Wide Field and Planetary Camera (WF/PC). The WF/PC is a duel two dimensional spectrophotometer with rudimentary polarimetric and transmission grating capabilities. The instrument operates from 1150 to 11000 A with a resolution of 0.1 arcsec per pixel or 0.043 arcsec per pixel. Data products and standard calibration methods are briefly summarized.

Beschreibung: The Hubble Space Telescope is described along with how its design affects the images produced at the Science Instruments. An overview is presented of the hardware. Details are presented of the focal plane, throughput of the telescope, and the point spread function (image of an unresolved point source). Some detailed simulations are available of this, which might be useful to observers in planning their observations and in reducing their data.

Beschreibung: The Faint Object Camera (FOC) is a long focal ratio, photon counting device designed to take high resolution two dimensional images of areas of the sky up to 44 by 44 arcseconds squared in size, with pixel dimensions as small as 0.0007 by 0.0007 arcseconds squared in the 1150 to 6500 A wavelength range. The basic aim of the handbook is to make relevant information about the FOC available to a wide range of astronomers, many of whom may wish to apply for HST observing time. The FOC, as presently configured, is briefly described, and some basic performance parameters are summarized. Also included are detailed performance parameters and instructions on how to derive approximate FOC exposure times for the proposed targets.

Beschreibung: The Fine Guidance Sensors (FGS) are a system of photomultiplier tubes and white light amplitude interferometers (Koester's prism) which are used for the fine guidance of the Hubble Space Telescope (HST). The purpose of the handbook is to provide information to a potential user of the FGS so that he may explore the feasibility of performing various observations. A brief overview is given of how the FGS works, along with an explanation of the instrument in some detail. The procedure for estimating exposure times is explained. The observing modes are described. Some details needed to specify the exposures and observation requirements on the proposal forms are explained. Data reduction procedures are outlined.

Beschreibung: The dynamics were studied of the solar corona through the imaging of large scale coronal structures with AS&E High Resolution Soft X ray Imaging Solar Sounding Rocket Payload. The proposal for this program outlined a plan of research based on the construction of a high sensitivity X ray telescope from the optical and electronic components of the previous flight of this payload (36.038CS). Specifically, the X ray sensitive CCD camera was to be placed in the prime focus of the grazing incidence X ray mirror. The improved quantum efficiency of the CCD detector (over the film which had previously been used) allows quantitative measurements of temperature and emission measure in regions of low x ray emission such as helmet streamers beyond 1.2 solar radii or coronal holes. Furthermore, the improved sensitivity of the CCD allows short exposures of bright objects to study unexplored temporal regimes of active region loop evolution.

Beschreibung: The FAUST telescope is an ultraviolet survey instrument that features a wide 8 deg field of view, 1-arcmin angular resolution, and a photon counting detector. Operating in the 1400-1800 A band, it will be sufficiently sensitive to detect blue m(v) = 17 objects in a single 20-minute night. The instrument is part of the ATLAS-1 shuttle mission, presently scheduled for flight in May 1991. A substantial number of high galactic latitude fields will be investigated, with particular emphasis on studies of the origin of the diffuse far UV background.

Beschreibung: In April 1990, Space Shuttle Discovery launched the Hubble Space Telescope (HST). An 18 month in-orbit update of the operations and performance of the HST is presented. Numerous color photographs are shown of objects already observed, and mission plans are presented for future observations by the HST.

Beschreibung: This video recording explains the science mission of the Broad Band X ray Telescope on board the Space Shuttle Columbia, December 1990. This tape was produced before launch.

Beschreibung: An overview of the mission of the Hubble Space Telescope, a joint project between NASA and the European Space Agency which will be used to study deep space, as well as our solar system is presented. The video contains animations depicting the Hubble Space Telescope in orbit, as well as footage of scientists at the Space Telescope Science Institute making real time observations. The images Hubble acquires will be downloaded into a database that contains images of over 19,000,000 celestial objects called the Star Catalog.

Beschreibung: Objectives of the Solar Optical Telescope are to study the physics of the Sun on the scale at which many of the important physical processes occur and to attain a resolution of 73km on the Sun or 0.1 arc seconds of angular resolution. Topics discussed in this overview of the Solar Optical Telescope include: why is the Solar Optical Telescope needed; current picture of the Sun's atmosphere and convection zone; scientific problems for the Solar Optical Telescope; a description of the telescope; the facility - science management, contamination control, and accessibility to the instruments; the scientific instruments - a coordinated instrument package for unlocking the Sun's secrets; parameters of the coordinated instrument package; science operations from the Space Shuttle; and the dynamic solar atmosphere.

Beschreibung: Surveys of the second quadrant of the Galaxy undertaken with the CfA 1.2-m telescope have been combined to produce a map of approximately 620 sq deg in the 2.6-mm CO (J = 1-0) line at high Galactic latitudes. CO was detected over about 13 percent of the region surveyed, an order of magnitude more gas by area than previously estimated. In contrast, only 26 percent of the area predicted by Desert et al. (1988) to contain molecular gas actually reveals CO, and about two-thirds of the clouds detected are not listed in their catalog of IR excess clouds.

Beschreibung: The machine-readable version of the atlas, as it is currently being distributed from the Astronomical Data Center, is described. The atlas represent a collection of spectra in the wavelength range 2.00 to 2.45 micros having a resolution of approximately 0.02 micron. The sample of 73 stars includes a supergiant, giants, dwarfs, and subdwarfs with a chemical abundance range of about -2 to +0.5 dex.

Beschreibung: A list of 1186 ultraviolet-excess objects (designated KUV) was compiled as a result of a search conducted with the 105-cm Schmidt telescope of the Kiso station of the Tokyo Astronomical Observatory. This document describes the machine readable version of the KUV survey list and presents a sample listing showing the logical records as they are recorded in the machine readable catalog. The KUV data include equatorial coordinates, magnitudes, color indices, and identifications for previously cataloged objects.

Beschreibung: The machine-readable version of the catalog, as it is currently being distributed from the astronomical data centers, is described. The catalog is a collection of spectrophotometric observations made using rotating grating scanners and calibrated with the fluxes of Vega. The observations cover various wavelength regions between about 330 and 1080 nm.

Beschreibung: The machine readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The Zodiacal Zone Catalog is a catalog of positions and proper motions for stars in the magnitude range where m sub v is between 4 and 10, lying within 16 deg of the ecliptic and north of declination -30 deg. The catalog contains positions and proper motions, at epoch, for equator and equinox J2000.0, magnitudes and spectral types taken mostly from the Smithsonian Astrophysical Observatory Star Catalog, and reference positions and proper motions for equinox and epoch B1950.0.

Beschreibung: In the early 1970's, the Smithsonian Astrophysical Observatory and the University of Arizona engaged in a cooperative program to develop a balloon-borne 102-cm telescope capable of carrying out far infrared (40 to 250 micron) observations of astronomical interest above the earth's atmosphere. Since 1972, the telescope has flown and successfully recovered a total of nineteen times. Thirteen of the flights produced high-quality astronomical data, resulting in more than 92.5 hours of photometric and spectroscopic observations of numerous objects, such as H 2 regions, dark clouds, molecular clouds, a planetary nebula, a galaxy, the galactic center, the planets, and an asteroid. From the launch site in Palestine, Texas, sources as far south as -50 degrees declination were observed. The balloon-borne telescope was one of the most sensitive instruments ever used for observation in the far infrared region of the spectrum. It was most productive in producing high resolution maps of large areas (typically square degrees) centered on known H 2 regions, molecular clouds, and dark cloud complexes. In many cases, these scans produced the first far infrared maps of these regions, and many new sources were discovered. The results have led to a better understanding of the distribution of gas and dust in these regions, the evolution of H 2 regions, and the processes of star formation in giant molecular clouds. The following topics are presented: (1) the focal plane instrumentation; (2) the history and flight record; (3) scientific results and publications; (4) eduational aspects; and (5) future planes.

Beschreibung: Optical spectrophotometry of PW Vulpeculae (Nova Vul 1984 no. 1) is combined with ultraviolet data to estimate electron temperatures, densities, and abundances in the ejecta of this slow classical nova. The reddening, distance, and evolution of the ultraviolet spectrum are also discussed. Abundances are nearly solar, with the exception of Nitrogen, which is substantially higher. Although Neon has been reported to be enhanced in several novae, it does not seem to be the case for PW Vul. Photoionization model calculations are presented of the ejecta that give a reasonable match of the observed emission spectrum. A strong featureless continuum shows that very hot, presumably shock heated, gas plays a major role in determining the energetics of this nova. Emission from this hot gas is responsible for the ionization of the nebular gas. A calculation of the masses of both the hot coronal gas and the cooler nebular gas shows that the former may account for most of the mass of the ejecta.

Beschreibung: Results are presented from observations, made with the SWP spectrograph at low resolution, of Tc-deficient S and C members of the group of chemically peculiar red giant (PRG) stars, which were carried out to search for possible companions to these stars. The results support the hypothesis of Little et al. (1987) and Smith and Lambert (1987, 1988) that the chemical peculiarities of T-deficient S and MS PRG stars have arisen due to mass transfer from white dwarf companions.

Beschreibung: The present study describes the STIS instrument concept and the role and requirements of the CCD detectors. Specific required properties and the current status of the efforts to meet them are discussed. The goals of the STIS team include studies of the origin and evolution of the solar system, star formation, variable stellar phenomena, the nature and energy balance of the interstellar and intergalactic medium, and the origin and evolution of galaxies and their nuclear activity. The STIS operating modes (spectral range, resolving power, effective area, and angular range) and the optical arrangement to accomplish them are presented. The detective quantum efficiency of several candidate detector types are shown as a function of wavelength for the four STIS bands. Difficulties that arise in the use of CCDs are discussed. Consideration is given to the requirements imposed on STIS CCDs and to their performance.

Beschreibung: The technology of the wide field planetary camera (WFPC-2) CCD technology is examined with reference to the WFPC-1 experience. Strategies are presented for elimination of quantum efficiency (QE) hysteresis and implementation of maintenance-free QE stability, improved far-UV performance, on-orbit photometric calibrations, refinements in CCD electronics, and anticipated CCD particle radiation effects. Absorption depth vs. wavelength in silicon and a cross section of the CCD membrane are shown.

Beschreibung: A description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility is presented and a summary of its observations and data reduction is given. The systems that make up the facility are a magnetograph telescope, an H alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.