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NASA NTRS1986

Coronal diagnostics.

This is an introduction to this part of the proceedings and an overview of coronal diagnostics. The current understanding of coronal loops is summarized. Included are observations from ground-based radio telescopes and from X ray telescopes lofted above the atmosphere, as well as theoretical interpretations of these observations. Also included in these introductory remarks is a discussion of the three dimensional structure of coronal loops. Alternative radiation mechanisms are then described within the context of both the radio and X ray emission. Various methods of determining the strength and structure of the coronal magnetic field are then described, followed by the coronae of nearby stars and future prospects for radio diagnostic of coronal loops.

Lang, Kenneth R.↗

NASA NTRS2005

International VLBI Service for Geodesy and Astrometry 2004 Annual Report

Contents include the following: Combination Studies using the Cont02 Campaign. Coordinating Center report. Analysis coordinator report. Network coordinator report. IVS Technology coordinator report. Algonquin Radio observatory. Fortaleza Station report for 2004. Gilmore Creek Geophysical Observatory. Goddard Geophysical and Astronomical observatory. Hartebeesthoek Radio Astronomy Observatory (HartRAO). Hbart, Mt Pleasant, station report for 2004. Kashima 34m Radio Telescope. Kashima and Koganei 11-m VLBI Stations. Kokee Park Geophysical Observatory. Matera GGS VLBI Station. The Medicina Station status report. Report of the Mizusawa 10m Telescope. Noto Station Activity. NYAL Ny-Alesund 20 metre Antenna. German Antarctic receiving Station (GARS) O'higgins. The IVS network station Onsala space Observatory. Sheshan VLBI Station report for 2004. 10 Years of Geodetic Experiments at the Simeiz VLBI Station. Svetloe RAdio Astronomical Observatory. JARE Syowa Station 11-m Antenna, Antarctica. Geodetic Observatory TIGO in Concepcion. Tsukuba 32-m VLBI Station. Nanshan VLBI Station Report. Westford Antenna. Fundamental-station Wettzell 20m Radiotelescope. Observatorio Astroonomico Nacional Yebes. Yellowknife Observatory. The Bonn Geodetic VLBI Operation Center. CORE Operation Center Report. U.S. Naval Observatory Operation Center. The Bonn Astro/Geo Mark IV Correlator.

Behrend, Dirk↗

NASA NTRS2007

Status on Iterative Transform Phase Retrieval Applied to the GBT Data

This slide presentation reviews the use of iterative transform phase retrieval in the analysis of the Green Bank Radio Telescope (GBT) Data. It reviews the NASA projects that have used phase retrieval, and the testbed for the algorithm to be used for the James Webb Space Telescope. It shows the comparison of phase retrieval with an interferometer, and reviews the two approaches used for phase retrieval, iterative transform (ITA) or parametric (non-linear least squares model fitting). The concept of ITA Phase Retrieval is reviewed, and the application to Radio Antennas is reviewed. The presentation also examines the National Radio Astronomy Observatory (NRAO) data from the GBT, and the Fourier model that NRAO uses to analyze the data. The challenge for ITA phase retrieval is reviewed, and the coherent approximation for incoherent data is shown. The validity of the approximation is good for a large tilt. There is a review of the proof of concept of the Phase Review simulation using the input wavefront, and the initial sampling parameters estimate from the focused GBT data.

Dean, Bruce↗

NASA NTRS2013

Mechanism for Deploying a Long, Thin-Film Antenna from a Rover

Observations with radio telescopes address key problems in cosmology, astrobiology, heliophysics, and planetary science including the first light in the Universe (Cosmic Dawn), magnetic fields of extrasolar planets, particle acceleration mechanisms, and the lunar ionosphere. The Moon is a unique science platform because it allows access to radio frequencies that do not penetrate the Earth's ionosphere and because its far side is shielded from intense terrestrial emissions. A radio antenna can be realized by using polyimide film as a substrate, with a conducting substance deposited on it. Such an antenna can be rolled into a small volume for transport, then deployed by unrolling, and a robotic rover offers a natural means of unrolling a polyimide film-based antenna. An antenna deployment mechanism was developed that allows a thin film to be deposited onto a ground surface, in a controlled manner, using a minimally actuated rover. The deployment mechanism consists of two rollers, one driven and one passive. The antenna film is wrapped around the driven roller. The passive roller is mounted on linear bearings that allow it to move radially with respect to the driven roller. Springs preload the passive roller against the driven roller, and prevent the tightly wrapped film from unspooling or "bird's nesting" on the driven spool. The antenna deployment mechanism is integrated on the minimally-actuated Axel rover. Axel is a two-wheeled rover platform with a trailing boom that is capable of traversing undulated terrain and overcoming obstacles of a wheel radius in height. It is operated by four motors: one that drives each wheel; a third that controls the rotation of the boom, which orients the body mounted sensors; and a fourth that controls the rover's spool to drive the antenna roller. This low-mass axle-like rover houses its control and communication avionics inside its cylindrical body. The Axel rover teleoperation software has an auto-spooling mode that allows a user to automatically deploy the thin-film antenna at a rate proportional to the wheel speed as it drives the rover along its trajectory. The software allows Axel to deposit the film onto the ground to prevent or minimize relative motion between the film and the terrain to avoid the risk of scraping and antenna with the terrain.

Lazio, Joseph↗

NASA NTRS2012

VHF Radio Response of the near Earth Space During Solar Activity Growth in October, 2003

The analysis of observations of very high frequency radio noise intensity at the middle latitude on a frequency f = 500 MHz from 14th till 26th of October, 2003 is presented. These data are compared with the solar radio bursts in the range of frequencies 1-14 MHz registered by RAD2 receiver of the WAVES device installed on board the WIND spacecraft. The sporadic enhancement of near Earth very high frequency radio noise were observed with the help of ground radio telescope preferably either in pre mid night hours or at daytime. In many cases between October 17 and 22 short-term increases of the fluxes of low energy electrons, protons and ions in the interplanetary space by hundreds of times, corresponded to VHF radio bursts. At the same time slow increasing of solar cosmic rays streams at Lagrange point L1 and on geostationary orbit during October, 21 and 22, did not affect the usual radio noise level. A strong solar flare of 1B/X5.5 class on October 23 contributed to a prolonged rise of the intensity level of spectral radio emission, including the night sector of magnetosphere. It is assumed that very high frequency radio bursts in the near Earth space may appear when the processes of penetration of interplanetary low energy charge particles into Earth plasmasphere take place.

Dudnik, O. V.↗

NASA NTRS2011

Monitoring Mars for Electrostatic Disturbances

The DSN radio telescope DSS-13 was used to monitor Mars for electrostatic discharges from 17 February to 11 April, 2010, and from 19 April to 4 May, 2011, over a total of 72 sessions. Of these sessions, few showed noteworthy results and no outstanding electrostatic disturbances were observed on Mars from analyzing the kurtosis of radio emission from Mars. Electrostatic discharges on mars were originally detected in June of 2006 by Ruf et al. using DSS-13. he kurtosis (normalized fourth moment of the electrical field strength) is sensitive to non-thermal radiation. Two frequencies bands, either 2.4 and 8.4 GHz or 8.4 and 32 GHz were used. The non-thermal radiation spectrum should have peaks at the lowest three modes of the theoretical Schumann Resonances of Mars. The telescope was pointed away from Mars every 5 minutes for 45 seconds to confirm if Mars was indeed the sources of any events. It was shown that by including a down-link signal in one channel and by observing when the kurtosis changed as the telescope was pointed away from the source that the procedure can monitor Mars without the need of extra equipment monitoring a control source.

electrostatic discharges↗

NASA NTRS1994

A six year timing solution for PSR B1951 + 32

Six years of pulse time-of-arrival measurements have been collected from observations of the young, fast pulsar PSR B1951 + 32 in the CTB 80 supernova remnant using the Jodrell Bank and Arecibo radio telescopes. The combined data allow for the determination of a phase connected solution between 1987 August 21 and 1993 September 21. This solution provides an accurate rotational ephemeris for high energy x-ray and gamma-ray observations of this source made during the six years of radio timing observations to an accuracy of better than one tenth of a pulse period (4 ms). The pulsar has an activity parameter comparable with the value seen in the Crab pulsar.

Foster, R. S.↗

NASA NTRS1991

Development of a moon-based magnetospheric and coronal imager using a large broadband array

The 'Missions to and from Planet Earth' mandated by President Bush in 1989 provide a unique opportunity for magnetospheric and coronal plasma physicists to cooperate with low frequency radio astronomers in the development of an advanced experiment designed for the lunar surface. A large active lunar based array would sound the Earth's magnetosphere at VLF frequencies and the solar corona at decametric wavelengths allowing plasma physicists to map both the Earth's magnetosphere and those regions in the solar corona that trigger precursors to solar flares. With the transmitter silent, the array would become the ideal low frequency radio telescope, examining both geospace emissions such as auroral kilometric radiation and extraterrestrial signals from the planets, pulsars, supernova remnants, and active galactic nuclei. Both experiments satisfy requirements mandated in both 'Mission to Planet Earth' and in 'Mission from Planet Earth.' By proposing a cooperative effort both communities (plasma physicists and radio astronomers) stand to benefit. Jim Green, Director of the NASA Space Science Data Center (NSSDC) at GSFC; Tony Phillips, Research Fellow at California Institute of Technology; T. D. Carr, Director of the University of Florida Radio Observatory (UFRO) and the author are enlisting the cooperation of the scientific community in defining the system specifications. Some components, such as the receivers, will be standard 'off-the-shelf' items, and hence will require little developmental research. However, the individual antenna elements and the phasing and matching networks will require some R&D to satisfy the frequency requirements (20 KHz-40 MHz). By flying the experiment in Earth orbit first, Dr. Green proposes to gather valuable magnetospheric data as well as to prove the principle of the large moon based experiment. He claims that funding for the preliminary ground based studies at the UFRO may be available as early as FY-92.

Lebo, George↗

NASA NTRS1986

Overview of the NASA SETI Program

The NASA Search of Extraterrestrial Intelligence (SETI) program plan is to scan the microwave window from 1 to 10 GHz with existing radio telescopes and sophisticated signal processing equipment looking for narrow band features that might represent artificial signals. A microwave spectrometer was built and is being field tested. A pattern recognition computer to search for drifting continuous wave signals and pulse trains in the output spectra is being designed. Equipment to characterize the radio frequency interference environment was also built. The plan is to complete the hardware and software by FY-88. Then, with increased funding, this equipment will be replicated in Very Large Scale Integration form. Observations, both a complete sky survey and a search fo nearby solar type stars, will begin in about 1990. The hypothesis that very powerful signals exist or that signals are being beamed at us will be tested. To detect the kinds of signals radiated at distances of 100 light years will require a collecting area kilometers in diameter.

Oliver, B. M.↗

NASA NTRS1978

Independent radio-occultation studies of Venus' atmospheres

Closed-loop frequency data from Mariner 10 have provided S and X-band temperature-pressure profiles for Venus' neutral atmosphere, as well as an S-band profile for the nightside ionosphere. The dual-frequency radio-occultation experiment was independently monitored by two radio telescopes: Goldstone and Owens Valley (X-band only). Comparisons are also made with data obtained from Mariner 5 and in-situ measurements from Veneras 8, 9, and 10. Attention is given to anomalies in the amplitude and frequency of spacecraft signals during their exit from the Venusian atmosphere, as evidenced by radio occultation.

Nicholson, P. D.↗

NASA NTRS1982

Transit telescope designs optimized for multiple object spectroscopy with fibers

Instruments to simultaneously study the spectra of many objects in the field of view of a telescope can be made using fused silica fibers. The spectrograph at the 2.3m telescope of the University of Arizona has been modified for such operation, and is used routinely to study the dynamics of galaxy clusters. Consideration has been given to how the multifiber technique can best be used to obtain spectra of the many faint objects identified by deep transit survey instruments and new space and radio telescopes. A transit survey such as that planned by McGraw et al. (1980), with CCDs at the focus of a 2m transit telescope, will identify objects down to 24th magnitude, and down to 22nd magnitude will give very complete data on variability and optical energy distribution. A telescope with much larger aperture is required for spectroscopic follow up. It is suggested that large telescopes dedicated to this type of work can be made and operated for only a fraction of the cost of a general-purpose telescope.

Angel, J. R. P.↗

NASA NTRS1992

Predicted galaxy counts in CO emission

The CO galaxy counts are predicted from studies of LCO in nearby galaxies, with consideration given to how these counts may be compared to the current understanding of recent galaxy evolution. The average number of galaxies per square degree with CO (1-0) emission above a brightness threshold of 4.5 x 10 exp -20 W/sq m is predicted to be 0.5 +/-4.0. The expressed uncertainty in the predicted galaxy counts comes primarily from uncertainties in the absolute scale and high-luminosity cutoff of the CO luminosity function. Using present-technology mm-radio telescopes and receivers, it is possible to employ galaxy counts in CO (1-0) emission to test theories of recent (z is less than about 0.4) galaxy evolution. If it is true that interactions among galaxies and consequent starbursts were more common in the recent past, as suggested by galaxy counts at far-IR and cm-radio wavelengths, then it is anticipated that the molecular emission of galaxies will increase with redshift and the CO galaxy counts will exceed this prediction based on nearby galaxies.

Verter, Frances↗

NASA NTRS2020

Investigating the Mini and Giant Radio Flare Episodes of Cygnus X-3

The microquasar Cygnus X-3 underwent a giant radio flare in April 2017, reaching a maximum flux of∼16.5 Jy at 8.5 GHz. We present results from a long monitoring campaign carried out with Medicina at 8.5, 18.6 and 24.1 GHz, in parallel to the Mets ̈ahovi radio telescope at 37 GHz, from 4 to 11 April 2017. We observe a spectral steepening fromα= 0.2 to 0.5 (with Sν∝ν−α) within 6 h around the epoch of the peak maximum of the flare, and rapid changes in the spectral slope in the following days during brief enhanced emission episodes while the general trend of the radio flux density indicated the decay of the giant flare. We further study the radio orbital modulation of CygX-3 emission associated with the 2017 giant flare and with six mini-flares observed in 1983, 1985, 1994,1995, 2002 and 2016. The enhanced emission episodes observed during the decline of the giant flare at 8.5 GHz coincide with the orbital phaseφ∼0.5 (orbital inferior conjunction). On the other hand the light curves of the mini-flares observed at 15−22 GHz peak atφ∼0, except for the 2016 light curve which is shifted of 0.5 w.r.t. the other ones. We attribute the apparent phase shift to the variable location of the emitting region along the bent jet. This might be explained by the different accretion states of the flaring episodes (the 2016 mini-flare occurred in the hypersoft X-ray state).

Elise Egron↗

NASA NTRS1980

Synthesized map of a solar filament at 6 cm with approximately 15 arc sec resolution

Radio telescope observations have been used to provide the first synthesized map of a filament at 6 cm with angular resolution of about 15 arcsec. The 'dirty' map of the north limb of the sun is shown along with the dirty map of the residual after subtracting the three component least squares model. There is very good correspondence between the radio contours and the H alpha filament; the darkest feature of the filament has a radio temperature depression of 7500 plus or minus 1500 K, and the corresponding brightness temperature of the filament is 12500 plus or minus 1500 K. It is concluded that for this particular filament the radio size is not larger than the optical one.

Rao, A. P.↗

NASA NTRS2008

Understanding Black Hole X-ray Binaries: The Case of Cygnus X-1

Black Hole X-ray Binaries are known to display distinct emission states that differ in their X-ray spectra, their X-ray timing properties (on times scales less than 1 s) and their radio emission. In recent years monitoring observations, specially with NASA's Rossi X-ray Timing Explorer (RXTE), have provided us with detailed empirical modeling of the phenomenology of the different states as well as a unification scheme of the long term evolution of black holes, transient and persistent, in terms of these states. Observations of the persistent High Mass X-ray Binary (HMXB) Cygnus X-l have been at the forefront of learning about black hole states since its optical identification through a state transition in 1973. In this talk I will present in depth studies of several different aspects of the accretion process in this system. The main data base for these studies is an ongoing RXTE and Ryle radio telescope bi-weekly monitoring campaign that started in 1997. I will discuss high-resolution timing results, especially power spectra, which first gave rise to the Lorentzian description now widely used for black hole and neutron star binaries, and time lags, which we found to be especially well suited to identify state transitions. The evolution of spectral, timing, and radio parameters over years will be shown, including the rms-flux relation and the observation of a clearly correlated radio/x-ray flare. We also observed Cygnus X-1 with INTEGRAL, which allowed us to extend timing and spectral studies to higher energies, with XMM, which provided strong constraints on the parameters of the 6.4 keV iron fluorescence line, and with Chandra, which provided the most in depth study to date of the stellar wind in this system. Models based on the physical conditions in the accretion region are still mainly concentrated on the one or other of the observational areas but they are expanding: as an example I will review results from a jet model for the quantitative description of the radio through X-ray spectra. I will conclude with an outlook on a truly multi-instrument observing campaign of Cygnus X-1 that was performed in 2008 April in order to better constrain the jet models mentioned above (and provide a unique data set for cross-calibration).

Pottschmidt, Katja↗

NASA NTRS1977

X-ray and radio observations of the structure of Abell 478

The complex X-ray and radio structures of the cluster of galaxies Abell 478 have been observed in the 2-11-keV energy band by the rotating modulation collimators on the SAS-3 X-ray observatory and at 1415 MHz by the Westerbork synthesis radio telescope. The X-ray data imply an extended source (X-ray luminosity of the order of 10 to the 45th power erg/s) and are consistent with the presence of a coincident pointlike source X-ray luminosity of the order of 10 to the 45th power erg/s. The X-ray source position is also coincident with a cD radio galaxy at the core of the cluster.

Schnopper, H. W.↗

NASA NTRS1990

A multi-wavelength study of the peculiar galaxy NGC 2976

Researchers are currently studying NGC 2976 at many wavelengths to investigate the extent to which an interaction with M81 may have affected the star formation history of this galaxy. Here, researchers present observations of NGC 2976 made at 50 microns with the high resolution (CPC) instrument onboard Infrared Astronomy Satellite (IRAS) at 21-cm (both HI line and radio continuum) with the Westerbork Synthesis Radio Telescope (WSRT) and in the H alpha line with the Kitt Peak National Observatory (KPNO) 36 inch telescope. The far infrared emission is not centrally peaked as in other spirals (e.g., Wainscoat et al. 1987), but has obvious intensity peaks near the ends of the disk. The ionized gas as inferred from the H alpha observations, is largely confined to two large, symmetrically placed emission regions near the ends of the disk. Finally, the HI and 21-cm radio continuum emission also exhibit this strongly double-peaked structure. At all of the above wavelengths the emission peaks are roughly coincident and lie approx. 1.2 minutes to the NW and approx. 1.1 minutes to the SE of the optical center of this galaxy.

Tacconi, L. J.↗

NASA NTRS1992

Report of the Working Design Group

The engineering study group in the LOUISA workshop was responsible for producing a preliminary general design for an optical synthetic aperture telescope on the Moon. This design is intended to be a test case for focusing continuing design studies. The scope of the design included consideration of the array geometry, individual telescopes, metrology, site attributes, and construction. However, no attempt was made to go into further depth in the design than to cover the essential characteristics of the instrument. The starting point for the array design was the lunar optical array discussed by Burke (1985). His array geometry followed the design and correlation procedure of the 27-element Very Large Array (VLA) radio telescopes near Socorro, New Mexico.

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