Search

Over the past 30 years, interest in extraterrestrial intelligence has progressed from philosophical discussion to rigorous scientific endeavors attempting to make contact. Since it is impossible to assess the probability of success and the amount of telescope time needed for detection, Search for Extraterrestrial Intelligence (SETI) Projects are plagued with the problem of attaining the large amounts of time needed on the world's precious few large radio telescopes. To circumvent this problem, the Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP) instrument operates autonomously in a piggyback mode utilizing whatever observing plan is chosen by the primary observer. In this way, large quantities of high-quality data can be collected in a cost-effective and unobtrusive manner. During normal operations, SERENDIP logs statistically significant events for further offline analysis. Due to the large number of terrestrial and near-space transmitters on earth, a major element of the SERENDIP project involves identifying and rejecting spurious signals from these sources. Another major element of the SERENDIP Project (as well as most other SETI efforts) is detecting extraterrestrial intelligence (ETI) signals. Events selected as candidate ETI signals are studied further in a targeted search program which utilizes between 24 to 48 hours of dedicated telescope time each year.

The following subject areas are covered: (1) the science program (star formation and origins of planetary systems; structure and evolution of the interstellar medium; stellar population; the galactic and extragalactic distance scale; nature of galaxy nuclei, AGNs, and QSOs; formation and evolution of galaxies at high redshifts; and cosmology); (2) implementation of the science program; (3) the observatory-class missions (HST; LST - the 6m successor to HST; and next-generation 16m telescope); (4) moderate and small missions (Delta-class Explorers; imaging astrometric interferometer; small Explorers; optics development and demonstrations; and supporting ground-based capabilities); (5) prerequisites - the current science program (Lyman-FUSE; HTS optimization; the near-term science program; data analysis, modeling, and theory funding; and archives); (6) technologies for the next century; and (7) lunar-based telescopes and instruments.

Analysis and interpretation continued on data generated by the flight of 27.086 in April of 1986 and by the successful UVX mission. Optical and mechanical design of the 1 meter EUV telescope, planned for launch with the large SPARTAN type carrier, ASTRO-SPAS, was also continued. The major effort centered on the preparation of flight 27.106, scheduled to launch in September, 1986. Work which was performed included: design of the skins and bulkheads; completion of the optical, mechanical, and electrical design; purchase of the major components of the instruments; assemblage of the electrical components; and performance of theoretical work, to support the data interpretation.

The Far Ultraviolet imager (FUVI) was flown on the Aries class sounding rocket 24.015, producing outstanding results. The diffuse extreme ultraviolet (EUV) background spectrometer which is under construction is described. It will be launched on the Black Brant sounding rocket flight number 27.086. Ongoing design studies of a high resolution spectrometer are discussed. This instrument incorporates a one meter normal incidence mirror and will be suitable for an advanced Spartan mission.

The HEAO A-2 low energy X-ray detectors have surveyed over 95% of the sky in the spectral bands 0.18-0.44 and 0.44-2.8 keV, down to a typical limiting sensitivity of 1 x 10 to the -11th and 3 x 10 to the -11th ergs per sq cm per sec in each band, respectively. Using a significance criterion of 6 sigma for existence, 114 sources are cataloged, of which 54 were previously undiscovered and 32 remain unidentified. The catalog contains a listing of all counterpart identifications and a cross-reference to all HEAO 1 A-2 low energy detector team publications on the catalog sources complete through the end of 1981. Supplementary material allows the estimation of spectral parameters for the spectral models from the observed intensities. Simple graphs allow the extraction of energy fluxes at the earth, both with and without the effects of interstellar absorption. The angular distribution of the cataloged sources in the 0.44-2.8 keV band is concentrated toward the galactic plane and resembles that seen at higher energy. The distribution in the 0.18-0.44 keV band is more uniform and contains many more newly discovered and unidentified sources.

The OAO-3 satellite was used for several months' observation of the loss mass X-ray binary sources 2A18822-371 and 4U2129+47 in a search for variability similar to the 35 day on-off cycle observed in Her X-1. The related system Cyg X-2 was observed both optically and in X-rays covering one complete binary cycle of 9.8 days. The UCL X-ray telescope observations revealed no periodities nor obvious variability other than the known orbital periods; however, the ground-based optical spectroscopy supports the interpretation of the photometry periodicities as representing orbital motion in 2A1822-371 and detected radial velocity motions on the photometric period in 4U2129+47. The shape and the length of the 4.8 hour periodicity in the X-ray emission from Cyg X-3 was also studied. The quality OAO-3 data obtained to measure the light curve and look for a change in the period and/or obtain improved measurement of the slope of the light curve was insufficient.

The Far Ultraviolet Space Telescope (FAUST) a compact, wide field-of-view, far ultraviolet instrument designed for astronomical observations of extended and point sources is discussed. The design and application of the instrument are described. The prime objective is to observe faint astronomical sources with sensitivities higher than previously available. Scientific programs will include: (1) a search for ultraviolet stars which are predicted to exist at the stage of evolution prior to the final death of a star; (2) observations of galaxies and quasars; and (3) joint programs with other Spacelab 1 experiments. The secondary objective is to verify the suitability of the Spacelab as a platform for far ultraviolet astronomy: data will be provided on the ultraviolet background levels due to astronomical, terrestrial, and spacecraft generated sources; the levels of contaminants which affect ultraviolet instruments; and the capability of the Orbiter for stable pointing at celestial sources for useful periods of time.

Questions concerning the optical identification of X-ray sources are considered. There are now a total of eight optically identified galactic X-ray sources. Of these eight, five are definitely established as binaries. The nature of the other three sources remains unknown. Studies of U Geminorum conducted on the basis of optical and X-ray observations are also discussed. From the upper limit to the accretion rate for U Gem obtained with the aid of soft X-ray data, it is seen that most of the mass flow in U Gem is lost from the system.

A Black Brant VC rocket was used to scan the Coma and Virgo clusters in order to measure structure in the X-ray sources. The rocket also made measurements of soft X-ray spectra, soft X-ray background flux during a 50 deg scan of the sky, soft X-rays from De Voucoulers 50, set limits to the energy dependence of soft X-ray background spectra, and the flux of solar 584 A radiation resonantly scattered by interstellar He flowing through the solar system.

The paper presents HEAO 1 low-energy X-ray observations of 59 known or suspected RS CVn systems cited in the lists of Hall (1976), Eggen (1978), and the circulars of the Working Group on RS CVn systems of IAU Commission 42. The data are used to argue against the validity of the minimum flux coronal models. A coronal loop model is used to derive expressions for the loop parameters in terms of observable quantities, and find acceptable solutions for RS CVn systems. It is concluded that the difference between solar activity and that observed in RS CVn systems may be merely a matter of scale.

The paper reports the detection of two X-ray flares from each of the nearby dMe stars, AT Mic and AD Leo, with the A-2 experiment on board HEAO 1. A spectrum obtained during the brighter AT Mic flare, the first X-ray spectrum of a stellar flare, is well matched by a thermal model with a temperature 3 x 10 to the 7 K and an iron K-alpha emission line. The X-ray luminosities derived are in the range 1.3-16 x 10 to the 30th ergs/s, while emission measures are in the range 1.1-14 x 10 to the 53rd/cu cm. The estimated Lx/Lopt ratios exceed unity and are inconsistent with Mullan's flare model. Several scenarios to explain this discrepancy are proposed.

During the summer of 1978 the recurrent transient X-ray source, Aquila X-1, underwent its first major outburst in two years. The results of extensive observations at X-ray and optical wavelengths throughout this event, which lasted for approximately two months are presented. The peak X-ray luminosity was approximately 1.3 times that of the Crab and exhibited spectral dependent flickering on timescales approximately 5 minutes. The observations are interpreted in terms of a standard accretion disk model withparticular emphasis on the similarities to Sco X-1 and other dward X-ray systems, although the transient nature of the system remains unexplained. It was found that Aquila X-1 can be described adequately by the semi-detached Roche lobe model and yields a mass ratio of less than or approximate to 3.5.

Evidence for a soft X-ray source at the location of the nova-like variable star MV Lyr is presented. Data from the smallest field of view of the A2 experiment on board HEAO-1 in the range 0.18 to 2.5 keV reveals a source of 0.18 to 0.43 keV emission, designated H1901+43, with a count rate corresponding to a flux of 4 x 10 to the -12th erg/sq cm per sec if a spectral temperature of 3 x 10 to the 5th K is assumed. The two-dimensional error box of H1901+43 is observed to contain the UX UMa star MV Lyr, which is suggested as the only obvious candidate for the source of X-ray emission, in accordance with the observations of soft X-ray emission from other cataclysmic variables, notably AM Her, U Gem and SS Cyg.

The HEAO-1 A-2 experiment, designed to study the large scale structure of the galaxy and the universe at X-ray energies is described. The instrument consists of six gas proportional counters of three types nominally covering the energy ranges of 0.15-3 keV, 1.2-20 keV, and 2.5-60 keV. The two low energy detectors have about 400 sq cm open area each while the four others have about 800 sq cm each. Dual field of view collimators allow the unambiguous determination of instrument internal background and diffuse X-ray brightness. Instrument characteristics and early performance are discussed.

Of the two 584 A channels in the helium glow detector, channel #1 appeared to provide data with erratic count rates and undue susceptibility to dayglow and solar contamination possibly because of filter fatigue or failure. Channel #3 data appear normal and of high quality. For this reason only data from this last channel was analyzed and used for detailed comparison with theory. Reduction and fitting techniques are described, as well as applications of the data in the study of nighttime and daytime Hel 584 A emission. A hot model of the interstellar medium is presented. Topics covered in the appendix include: observations of interstellar helium with a gas absorption cell: implications for the structure of the local interstellar medium; EUV dayglow observations with a helium gas absorption cell; and EUV scattering from local interstellar helium at nonzero temperatures: implications for the derivations of interstellar medium parameters.

Follow-on studies to the Apollo-Soyuz Extreme Ultraviolet Telescope experiment (MA-083) include analyses of individual target stars or classes of stars, not only with regard to the EUV data but also in connection with theoretical models and observations in other parts of the spectrum. Topics discussed include: observations of SS Cygni, Proxima Centauri, HZ 43, and Feige 24; computer searches for new EUV sources; Sirius: models and inferences; EUV emission from a hot gas; and the diffuse EUV background.

The adaptation of an extreme ultraviolet astronomy rocket payload for flight on the shuttle was studied. A sample payload for determining integration and flight procedures for experiments which may typically be flown on shuttle missions was provided. The electrical, mechanical, thermal, and operational interface requirements between the payload and the orbiter were examined. Of particular concern was establishing a baseline payload accommodation which utilizes proven common hardware for electrical, data, command, and possibly real time monitoring functions. The instrument integration and checkout procedures necessary to assure satisfactory in-orbit instrument performance were defined and those procedures which can be implemented in such a way as to minimize their impact on orbiter integration schedules were identified.

High intensity continuous gas discharge line source for extreme UV with low electromagnetic interference

Line emission in diffuse cosmic X ray continuum, discussing probable interstellar or intergalactic matter source

Acquisition and processing of X ray data from Southern Hemisphere sky

Sco XR-1 optical intensity power spectra oscillations searched for in pulsar frequencies and fundamental radial mode vibrations in white dwarfs and neutron stars

Extragalactic objects 3C 273 NGC 5128 and M87 X ray emission detection, using proportional counters on Aerobee 150 rocket

Far UV photometer for space research, isolating specific bands by combining spectral response of individual solar blind photocathodes with thin metallic films transmission qualities

X ray scattering by interstellar grains in direction of Crab pulsar and Sco XR-1

Aerobee payload and other instrumentation for studies in galactic X ray astronomy

Soft x ray extragalactic background flux measurements, considering correction for absorption by interstellar medium