scholarly journals 40. Radio Astronomy (Radio Astronomie)

1991 ◽  
Vol 21 (1) ◽  
pp. 449-475
Keyword(s):  
Radio Source ◽  
Radio Telescope ◽  
Radio Astronomy ◽  
Aperture Synthesis ◽  
Considerable Progress ◽  
Radio Interferometry ◽  
Owens Valley ◽  
Digital Correlator ◽  
Under Construction

The following commission members have contributed to this report:W.J. Altenhoff, H. Andernach, J. Baars, R. Chini, R.J. Cohen, J.J. Condon, Y. Fukui, R. Güsten, J.M. van der Hulst, C. Henkel, W. Huchtmeier, M. Ishiguro, T. Krichbaum, M, Kundu, A. Lazenby, W. Reich, P. Roelfsema, S.E. Thorsett, R. Tuffs, CM. Walmsley, H. Wendker, R. Wielebinski, T.L. Wilson (organizer), A. WitzelAperture Synthesis Telescopes - Commissioning tests and observations have been made using three antennas in the Australia Telescope (AT), spaced up to 2km apart, and the first image of a radio source observed at 6cm was produced in 1989. The IRAM millimeter array in France comprizing three 15-m antennas has been commissioned at 3mm. A fourth antenna is planned as well as operation at 1mm. The three element Berkeley-Illinois-Maryland Array (BIMA) at Hat Creek is being expanded to six 6-m antennas and a new correlator with 1024 channel up to 830MHz bandwidth. Plans to expand to 9 antennas are final. The Owens Valley three-element millimeter array has been operated at 1mm, the shortest wavelength for the radio interferometry; a digital correlator with 500MHz bandwidth is under construction and the array will be extended to 6 antennas. In Japan at NRO the Nobeyama Millimeter Array equipped with SIS receivers and 320MHz bandwidth "FX" correlator is now operational at 3mm and 7mm wavelengths. New SIS receivers for 1mm and 2mm are under construction and a sixth 10-m antenna is planned. The Cambridge 5-km telescope, now the Ryle Telescope, has been substantially upgraded. The overall sensitivity of the instrument is being increased by a factor of ~20. The Giant Metrewave Radio Telescope, being built at Khodad near Pune in India, has made considerable progress and is expected to be operational by 1992-93.

scholarly journals VLBI Measurements of Radio Source Positions at Three U.S. Stations

1981 ◽  
Vol 63 ◽  
pp. 329-336
Author(s):  
Shu-Hua Ye
Keyword(s):  
Radio Source ◽  
Radio Astronomy ◽  
Data Reduction ◽  
Geodetic Survey ◽  
Time Span ◽  
National Geodetic Survey ◽  
Owens Valley ◽  
Radio Observatory ◽  
The U.S

AbstractResults of VLBI measurement of 14 radio source positions at three U.S. stations during the MERIT short campaign is presented. Comparisons with other solutions are given, together with the comparisons between several radio source catalogues.During the MERIT short campaign, several observatories cooperated in VLBI measurements organized jointly by the U.S. National Geodetic Survey (NGS) and the National Aeronautics and Space Administration (NASA). There were two 7-day observations arranged from Sept. 26 to Oct. 2 and from Oct. 16 to Oct. 22, with time span nearly 23 hours per day. Details of the observation and data reduction have been published elsewhere (1). This paper deals with radio source positions determined by three U.S. stations, the Haystack Observatory, the Harvard Radio Astronomy Station (HRAS) and the Owens Valley Radio Observatory (OVRO).

scholarly journals Demonstrating the Principles of Aperture Synthesis with Table- Top Laboratory Exercises

2019 ◽  
Vol 200 ◽  
pp. 02004
Author(s):  
J.M. Marr ◽  
A.E.E. Rogers ◽  
V.L. Fish ◽  
F.P. Wilkin ◽  
M.B. Arndt ◽  
...  
Keyword(s):  
Radio Astronomy ◽  
Fourier Transforms ◽  
Aperture Synthesis ◽  
Fluorescent Light ◽  
College Level ◽  
Radio Interferometry ◽  
Hands On ◽  
Computer Activity ◽  
User Friendly ◽  
Signal Sources

Many undergraduate radio astronomy courses are unable to give a detailed treatment of aperture synthesis due to time constraints and limited math backgrounds of students. We have taken a laboratory-based approach to teaching radio interferometry using a set of college-level, table-top exercises. These are performed with the Very Small Radio Telescope (VSRT), an interferometer developed at the Haystack Observatory using satellite TV electronics as detectors and compact fluorescent light bulbs as microwave signal sources. The hands-on experience provided by the VSRT in these labs allows students to gain a conceptual understanding of radio interferometry and aperture synthesis without the rigorous mathematical background traditionally required. The data are quickly and easily processed using a user-friendly data analysis Java package, VSRTI_Plotter.jar. This software can also be used in the absence of the equipment as an interactive computer activity to demonstrate an interferometer’s responses to assorted surface brightness distributions. The students also gain some familiarity with Fourier transforms and an appreciation for the Fourier relations in interferometry using another Java package, the Tool for Interactive Fourier Transforms (TIFT). We have successfully used these tools in multiple offerings of our radio astronomy course at Union College

scholarly journals A distinct negative leader propagation mode

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
O. Scholten ◽  
B. M. Hare ◽  
J. Dwyer ◽  
N. Liu ◽  
C. Sterpka ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Electric Discharge ◽  
Radio Astronomy ◽  
Propagation Mode ◽  
Common Phenomenon ◽  
High Charge ◽  
Initial Stage ◽  
Lightning Initiation ◽  
The Common

AbstractThe common phenomenon of lightning still harbors many secrets such as what are the conditions for lightning initiation and what is driving the discharge to propagate over several tens of kilometers through the atmosphere forming conducting ionized channels called leaders. Since lightning is an electric discharge phenomenon, there are positively and negatively charged leaders. In this work we report on measurements made with the LOFAR radio telescope, an instrument primarily build for radio-astronomy observations. It is observed that a negative leader rather suddenly changes, for a few milliseconds, into a mode where it radiates 100 times more VHF power than typical negative leaders after which it spawns a large number of more typical negative leaders. This mode occurs during the initial stage, soon after initiation, of all lightning flashes we have mapped (about 25). For some flashes this mode occurs also well after initiation and we show one case where it is triggered twice, some 100 ms apart. We postulate that this is indicative of a small (order of 5 km$$^2$$ 2 ) high charge pocket. Lightning thus appears to be initiated exclusively in the vicinity of such a small but dense charge pocket.

Multi-wavelength Optical Aperture Synthesis

1992 ◽  
Vol 10 (1) ◽  
pp. 71-73 ◽  
Author(s):  
R.G. Marson ◽  
T.R. Bedding ◽  
J.G. Robertson
Keyword(s):  
Radio Astronomy ◽  
Angular Resolution ◽  
Diffraction Limit ◽  
Double Star ◽  
Aperture Synthesis ◽  
Angular Diameter ◽  
Optical Aperture ◽  
Multi Wavelength ◽  
Red Giant ◽  
Large Telescopes

AbstractThe technique of aperture synthesis is well developed in radio astronomy. When applied to the optical regime, aperture synthesis allows one to partially overcome the blurring effects of the atmosphere and increase the angular resolution of large telescopes to the diffraction limit. MAPPIT (Masked APerture-Plane Interference Telescope) is a multi-element interferometer which operates at the coude focus of the 3.9 m Anglo-Australian Telescope. This instrument has recently been reconfigured to operate in a dispersed mode so that simultaneous observations in a band of wavelengths are possible. We will discuss this instrument’s new mode and present observations of the double star δ Sco and an angular diameter of the previously unresolved red giant β Gru.

scholarly journals INTERSTELLAR MEDIUM AND DECAMETER RADIO SPECTROSCOPY

2021 ◽  
Vol 26 (4) ◽  
pp. 314-325
Author(s):  
S. V. Stepkin ◽  
◽  
O. O. Konovalenko ◽  
Y. V. Vasylkivskyi ◽  
D. V. Mukha ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Radio Telescope ◽  
Radio Astronomy ◽  
Low Frequency ◽  
Spectral Lines ◽  
Physical Parameters ◽  
Recombination Mechanism ◽  
Radio Recombination Lines ◽  
Radio Spectroscopy ◽  
Correlation Spectrum

Purpose: The analytical review of the main results of research in the new direction of the low-frequency radio astronomy, the interstellar medium radio spectroscopy at decameter waves, which had led to astrophysical discovery, recording of the radio recombination lines in absorption for highly excited states of interstellar carbon atoms (more than 600). Design/methodology/approach: The UTR-2 world-largest broadband radio telescope of decameter waves optimally connected with the digital correlation spectrum analyzers has been used. Continuous modernization of antenna system and devices allowed increasing the analysis band from 100 kHzto 24 MHz and a number of channels from 32 to 8192. The radio telescope and receiving equipment with appropriate software allowed to have a long efficient integration time enough for a large line series simultaneously with high resolution, noise immunity and relative sensitivity. Findings: A new type of interstellar spectral lines has been discovered and studied, the interstellar carbon radio recombination lines in absorption for the record high excited atoms with principal quantum numbers greater than 1000. The line parameters (intensity, shape, width, radial velocity) and their relation ship with the interstellar medium physical parameters have been determined. The temperature of line forming regions is about 100 K, the electron concentration up to 0.1 cm–3 and the size of a line forming region is about 10 pc. For the first time, radio recombination lines were observed in absorption. They have significant broadening and are amplified by the dielectronic-like recombination mechanism and are also the lowest frequency lines in atomic spectroscopy. Conclusions: The detected low-frequency carbon radio recombination lines and their observations have become a new highly effective tool for the cold partially ionized interstellar plasma diagnostics. Using them allows obtaining the information which is not available with the other astrophysical methods. For almost half a century of their research, a large amount of hardware-methodical and astrophysical results have been obtained including a record number of Galaxy objects, where there levant lines have been recorded. The domestic achievements have stimulated many theoretical and experimental studies in other countries, but the scientific achievements of Ukrainian scientists prove the best prospects for further development of this very important area of astronomical science. Key words: low-frequency radio astronomy; radio telescope; interstellar medium; radio recombination lines; carbon; hydrogen; spectral analyzer

scholarly journals Status of the Thai 40-m Radio Telescope

2017 ◽  
Vol 13 (S337) ◽  
pp. 346-347
Author(s):  
Phrudth Jaroenjittichai
Keyword(s):  
Radio Telescope ◽  
Radio Astronomy ◽  
Time Domain ◽  
Phased Array ◽  
Low Frequency ◽  
Great Leap ◽  
Great Leap Forward ◽  
Astronomical Research ◽  
L Band ◽  
K Band

AbstractSince the first light of the 2.4-m Thai National Telescope in 2013, Thailand foresees another great leap forward in astronomy. A project known as “Radio Astronomy Network and Geodesy for Development” (RANGD) by National Astronomical Research Institute of Thailand (NARIT) has been approved for year 2017-2021. A 40-m radio telescope has been planned to operate up to 115-GHz observation with prime-focus capability for low frequency and phased array feed receivers. The telescope’s first light is expected in late 2019 with a cryogenics K-band and L-band receivers. RFI environment at the site has been investigated and shown to be at reasonable level. A 13-m VGOS telescope is also included for geodetic applications. Early single-dish science will focus on time domain observations, such as pulsars and transients, outbursts and variability of maser and AGN sources.

Solar Radio Astronomy at Low Frequencies

2002 ◽  
Vol 199 ◽  
pp. 415-425
Author(s):  
Monique Pick
Keyword(s):  
Radio Telescope ◽  
Radio Astronomy ◽  
Coronal Mass Ejections ◽  
Solar Radio ◽  
Electron Beams ◽  
Solar Physics ◽  
Interplanetary Shocks ◽  
Radio Observations ◽  
Low Frequencies ◽  
Solar Radio Astronomy

This review is concerned to study of sun at frequencies lower than 1.4 GHz. Emphasis is made on results which illustrate the topics in which GMRT could play a major role. Coordinated studies including spectral and imaging radio observations are important for research in solar physics. Joint observations between the Giant Meter Radio Telescope (GMRT) with radio instruments located in the same longitude range are encouraged. This review inludes three distinct topics: Electron beams and radio observations- Radio signatures of Coronal Mass Ejections- Radio signatures of coronal and interplanetary shocks.

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