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Topic: Very Long Baseline Interferometry

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	Very Long Baseline Interferometry - Wikipedia, the free encyclopedia
		Very Long Baseline Interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy, in which the data received at each antenna in the array is paired with timing information, usually from a local atomic clock, and then stored for later analysis on magnetic tape or hard disk.
		The resolution achievable using interferometry is proportional to the distance between the antennas furthest apart in the array.
		As the phase of each complex visibility measurement cannot be determined with a very long baseline interferometer the symmetry of the corresponding contribution to the source brightness distributions is not known.
	en.wikipedia.org /wiki/Very_Long_Baseline_Interferometry (1381 words)

	Closure phase - Wikipedia, the free encyclopedia
		The closure phase is an observable quantity in imaging interferometry, which allowed the use of interferometry with very long baselines.
		The radio signals received are recorded onto magnetic tapes and sent to a laboratory as described in the article on Very Long Baseline Interferometry.
		Because of this property, it is widely used for interferometric imaging in radio astronomy and optical interferometry.
	en.wikipedia.org /wiki/Closure_phase (340 words)

	Untitled Document (Site not responding. Last check: 2007-10-22)
		Optical interferometry proved to be a quantum leap forward in the field of astrometry for the angular measurement of stars.
		Cross-correlation of signals is critical to the operation of long baseline interferometers since the signals to be combined are complex.
		Very long baseline interferometry is now capable of reaching resolutions on scales of 10^-3 to 10^-4 arcseconds from fringe patterns with positional accuracies of 10^-3 arcseconds.
	www1.wcf.net /~radduci/Papers/606-p.html (5460 words)

	NRC-HIA: Space Very Long Baseline Interferometry
		Although the space radio antenna is small compared to the large ground radio telescopes that are currently operational, the wide recording bandwidths yield interferometer sensitivities that allow for a large range of scientific purposes.
		In the long term very large antennas on the ground may be used in conjunction with antennas in space.
		Because of the very small linear scales imaged by the resolution of these telescopes (either in the sources themselves or in the intervening medium through which the sources will be observed), almost all of the observed phenomena will be time variable on the scale of the mission lifetimes (often much shorter).
	www.hia-iha.nrc-cnrc.gc.ca /projects/vlbi_e.html (1023 words)

	1993 VLBA Summer School Proceedings
		A brief overview of the fundamental principles underlying radio interferometry is presented using the terminology of modern optics.
		The Very Long Baseline Array (VLBA) is a highly flexible radio telescope designed for research in high resolution astronomy and geodesy.
		The top-level design goals for the Very Long Baseline Array are discussed and details of the design and performance of the antennas are presented.
	www.cv.nrao.edu /vlbabook (1085 words)

	ESA - Science - Home - Observations: Very Long Baseline Interferometry (VLBI)
		The angular resolution of a particular telescope depends on two main parameters: its diameter and the wavelength of the signal it is receiving.
		The angular resolution of the resulting image is as good as that obtained from a single antenna with a diameter equal to the largest separation (or ‘baseline’) between the individual antennas.
		The Very Long Baseline Interferometry (VLBI) technique — the ultimate case of interferometry — was originally developed in the 1960s by astronomers who were seeking ways to push the angular resolution of radio telescopes to the limits for studies of distant celestial objects.
	www.esa.int /esaSC/SEM8FUXDE2E_index_0.html (402 words)

	Smithsonian Astrophysical Observatory (SAO) (Site not responding. Last check: 2007-10-22)
		In Very Long Baseline Interferometry (VLBI), signals from a distant cosmic object are observed and recorded by widely separated radio telescopes.
		The signals are combined to produce an image of the radio source, with resolution equal to that achieved by a single giant telescope, thousands of kilometers across.
		The high velocities measured suggest the presence of a giant concentration of mass equivalent to 40 million Suns -- a fl hole -- at the galaxy's core.
	cfa-www.harvard.edu /cfa/ep/brochure/vlbi.html (176 words)

	Degree-1 Earth deformation from very long baseline interferometry measurements
		The presence of degree-1 deformations in very long baseline interferometry (VLBI) measurements is detected for the first time.
		For the period 1996–2001, 14 baselines out of 35 are significantly correlated (5% significance level).
		For the period 1985–2001, a sinusoidal fit to the GPS load-moment series predicts baseline series at all VLBI epochs, 49 out of 110 baselines are significantly correlated (5% significance level).
	www.agu.org /pubs/crossref/2002/2002GL015883.shtml (251 words)

	Very Long Baseline Interferometry (Site not responding. Last check: 2007-10-22)
		The Ny-Ålesund facility occupies a unique position near the North Pole and is able to collaborate with any observatory on the Northern hemisphere (see figure 2).
		The lack of nearby, large populated areas and the strict governmental monitoring of human activities on the Spitsbergen Islands ensures a very quiet microwave environment.
		It validates other geodetic results and provides the long term stability needed for long time series observations.
	www.statkart.no /skgd/nyaales/vlbi.html (459 words)

	D S N Advanced Tracking and Observational Techniques Home Page
		Very Long Baseline Interferometry (VLBI) is the radio astronomy technique which permits observation of celestial sources with the highest achievable angular resolution in modern astronomy.
		Because of the high sensitivity of the DSN antennas and their location, relative to other radio observatories around the Earth, DSN antennas have been used for VLBI since pioneering experiments in late 1960s.
		At present, the DSN antennas are regularly used for VLBI observations together with international VLBI radio astronomy networks: European VLBI (EVN) network, Very Long Baseline Array (VLBA/USA), Asian Pacific Telescope (APT), and in the Global VLBI sessions.
	dsnscience.jpl.nasa.gov /vlbi.html (332 words)

	CSRS :: Canadian Spatial Reference System - What is Very Long Baseline Interferometry
		VLBI, or Very Long Baseline Interferometry is a technique used to determine very precise distances between radio telescopes in order to study the earth, it's place in the universe and to monitor the changes in both.
		VLBI uses radio signals from deep space to measure how the continents are moving, how the spin rate of the earth is changing, the motion of the pole and even how the earth 'wobbles' in space.
		The size of the earth, it's shape, the changing orientation of it's polar axis and varying spin rate have all been determined by observing the stars and have all played a major role in our present understanding of the earth's structure.
	www.geod.nrcan.gc.ca /geodesy/vlbi/index_e.php (351 words)

	Very Long Baseline Connected Interferometry via the STM-16 ATM Network (ResearchIndex) (Site not responding. Last check: 2007-10-22)
		The very long baseline interferometry (VLBI) observed data...
		3 Evaluation of repeatability of baseline lengths in the VLBI..
		2 Very long baseline interferometry with large effective bandw..
	citeseer.ist.psu.edu /353486.html (241 words)

	NRAO OVLBI Home Page
		The Orbiting VLBI tracking station in Green Bank, West Virginia is one of four NASA tracking stations dedicated to support of Very Long Baseline Interferometry satellites.
		Current and future satellites extend interferometry baselines beyond the diameter of the earth.
		Researchers at JPL and their colaborators are planning a next generation space radio telescope, ARISE, Advanced Radio Interferometry between Space and Earth.
	www.gb.nrao.edu /ovlbi/OVLBI.html (1148 words)

	A two-step approach to analyze European geodetic Very Long Baseline Interferometry (VLBI) data (ResearchIndex) (Site not responding. Last check: 2007-10-22)
		Abstract: Since 1990 the European fixed station geodetic Very Long Baseline Interferometry (VLBI) network has been observing on a regular basis in order to determine crustal motion in Europe.
		Usually the analyses of geodetic VLBI data are set up in two different ways: a) to produce station coordinates for each observation epoch from independent parameter adjustments and b) to compute station coordinates at a reference epoch together with drift rate components simultaneously from solutions where station...
		Crustal motion in Europe determined with geodetic Very Long..
	citeseer.ist.psu.edu /206520.html (220 words)

	Very Long Baseline Interferometry (VLBI) Observing at Arecibo (Site not responding. Last check: 2007-10-22)
		Very Long Baseline Interferometry (VLBI) Observing at Arecibo
		NAIC presently commits Arecibo to supporting VLBI observing up to a maximum of 4% of the 305-m's observing time.
		Amounts of data can also be transferred off-line to the JIVE correlator by ftp, permitting (for example) establishment of fringes pre-observation.
	www.naic.edu /~astro/guide/node10.html (326 words)

	Welcome to JIVE
		JIVE is the Joint Institute for Very Long Baseline Interferometry in Europe.
		It was created by the European Consortium for VLBI and is a member of the European VLBI Network (EVN).
		The Panel's Evaluation Report is very positive and was approved by the ESF Executive Board a few days ago.
	www.jive.nl (541 words)

	Geoscience Australia: Geodesy - Very Long Baseline Interferometry (VLBI) Geodetic Technical Reports
		Very Long Baseline Interferometry (VLBI) Geodetic Technical Reports
		This is an index of Very Long Baseline Interferometry (VLBI) online Geodesy's Technical Papers either published in journals or presented by Geoscience Australia staff at recent meetings and conferences.
		The number of baselines under study is 190, correspondingly.
	www.ga.gov.au /geodesy/reports/vlbi (352 words)

	Citebase - Testing Relativistic Effect of Propagation of Gravity by Very-Long Baseline Interferometry
		Authors: Kopeikin, Sergei M. It is shown that the finite speed of gravity affects very-long baseline interferometric observations of quasars during the time of their line-of-sight close angular encounter with Jupiter.
		The present Letter suggests a new experimental test of general relativity in which the effect of propagation of gravity can be directly measured by very-long baseline interferometry as an excess time delay in addition to the logarithmic Shapiro time delay (Shapiro, I. I., 1964, Phys.
		The extra time delay caused by Jupiter on the 8th of September 2002 can be measured by advanced VLBI (very long baseline interferometry).
	citebase.eprints.org /cgi-bin/citations?id=oai:arXiv.org:gr-qc/0105060 (1206 words)

	Very Long Baseline Radio Interferometry (VLBI)
		To date, geocentric coordinates have been measured for about 120 sites, both fixed and "mobile", using the bandwidth synthesis Mark-III (or equivalent) technique.
		More than half of these have sufficiently long histories that reliable three-dimensional velocity estimates are also available.
		Likewise, celestial coordinates have been determined for more than 600 radio sources.
	www.iers.org /iers/earth/techniques/vlbi.html (192 words)

	Modeling of nutation-precession: Very long baseline interferometry results
		Analysis of over 20 years of very long baseline interferometry data (VLBI) yields estimates of the coefficients of the nutation series with standard deviations ranging from 5 microseconds of arc (μas) for the terms with periods <400 days to 38 μas for the longest-period terms.
		The largest deviations between the VLBI estimates of the amplitudes of terms in the nutation series and the theoretical values from the Mathews-Herring-Buffett (MHB2000) nutation series are 56 ± 38 μas (associated with two of the 18.6 year nutations).
		Citation: Herring, T. Mathews, and B. Buffett (2002), Modeling of nutation-precession: Very long baseline interferometry results, J.
	www.agu.org /pubs/crossref/2002/2001JB000165.shtml (366 words)

	Frequently Asked Questions About Radio Astronomy
		The VLA got its name because it is an array of radio telescopes and it is very large.
		In its very early conceptual and planning stages, "Very Large Array" was a working title, probably not intended to be the final name for the facility.
		Radio observations as part of a Search for Extraterrestrial Intelligence (SETI) have been done by different groups of researchers for a number of years, but this type of work is not a part of NRAO observational programs.
	www.aoc.nrao.edu /intro/faq.html (1395 words)

	Goddard Space Flight Center's Very Long Baseline Interferometry (Site not responding. Last check: 2007-10-22)
		The latest official GSFC VLBI ITRF quarterly solution (2005e, December 2005), quarterly intensive solution (Int15) and their associated earth orientation (eop) products can now be accessed through this web site's Data and Results page.
		Welcome to the home page of the GSFC VLBI Group--the NASA Goddard Space Flight Center's Very Long Baseline Interferometry (VLBI) group.
		VLBI is a geodetic technique that uses radio signals from quasars to measure movements of the Earth's crust and the rotation of the Earth.
	lupus.gsfc.nasa.gov (160 words)

	Find in a Library: Very long baseline interferometry and the VLBA : proceedings of a summer school held in Socorro, New ...
		Find in a Library: Very long baseline interferometry and the VLBA : proceedings of a summer school held in Socorro, New Mexico, June 23-30, 1993
		Very long baseline interferometry and the VLBA : proceedings of a summer school held in Socorro, New Mexico, June 23-30, 1993
		WorldCat is provided by OCLC Online Computer Library Center, Inc. on behalf of its member libraries.
	worldcatlibraries.org /wcpa/ow/bae15bb7a40d3c8da19afeb4da09e526.html (102 words)

	ETHZ IfA: Very Long Baseline Interferometry of Nearby Stars (Site not responding. Last check: 2007-10-22)
		With the discovery of strong radio emission from nearby stars the interest in Very Long Baseline Interferometry (VLBI) has increased.
		We hope to resolve the coronae with the present observing campaing, detect possible active regions, observe their rotation and evolution.
		As a spin off, very accurate astrometric positions will result that may serve to detect small companions of the stars.
	www.astro.phys.ethz.ch /research/benz/vlbi_nf.html (184 words)

	Very Long Baseline Interferometry (Site not responding. Last check: 2007-10-22)
		Radio astronomers can combine data from two telescopes that are very far apart and create images which have the same resolution as if they had a single telescope with a lens as big as the distance between the two telescopes.
		This means radio telescope arrays can see incredibly small details.
		Figure 1 Keck's 10 meter uses VLBI techniques to produce superior images to conventional telescopes.
	ffden-2.phys.uaf.edu /211.fall2000.web.projects/MMA/mvl.htm (64 words)

	Stellar Evolution - Black Holes
		The existence of mass concentration in ‘dark stars’ however, where their gravitational force was such that light couldn’t escape from them, was first postulated in the late 18th century by Reverend John Mitchell and subsequently in the very late 18th century by Pierre-Simon Laplace (Bunn 1995, Thinkquest 1999).
		These super massive fl holes are very large and are of the order of up to billions of solar masses (Britt 2003).
		If primordial quantum fl holes existed early in the history of the Universe it is very likely that some of these, being extremely small, would have radiated away (Schomberg 2002) via Hawking radiation.
	astronomyonline.org /Stars/BlackHole.asp?Cate=Stars&SubCate=OG04&SubCa... (5984 words)

	Dr. Zook's Lab (Site not responding. Last check: 2007-10-22)
		Zook's research interests include astronomy and optics, with such research areas as optical phase conjugation in nonlinear materials and observational work on quasars using Very Long Baseline Interferometry (VLBI).
		Another area of research interest deals with the physical nature of "good" musical tone quality in wind instruments.
		This area of research is an outgrowth of another interest of mine, playing the oboe and English horn in both the Pomona College Symphony Orchestra and the Pomona College Concert Band."
	www.physics.pomona.edu /visitors/place/zookres.html (109 words)

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